codegen: add ability to insert comments and blank lines into the generated code

.gitignore

@@ -1 +1,6 @@
 sample_data/data
+
+# Legacy versions
+.cmd-old/
+pkg/.testapp
+.claude

cmd/subcmd_generate_models.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"fmt"
 	"go/ast"
-	"go/printer"
 	"go/token"
 	"os"
 
@@ -37,46 +36,49 @@ var generate_model = &cobra.Command{
 			return ErrNoSuchTable
 		}
 
-		fset := token.NewFileSet()
-
 		if Must(cmd.Flags().GetBool("test")) {
 			file2 := modelgenerate.GenerateModelTestAST(table, modname)
-			PanicIf(printer.Fprint(os.Stdout, fset, file2))
+			PanicIf(modelgenerate.FprintWithComments(os.Stdout, file2))
 		} else {
-			file := &ast.File{
-				Name: ast.NewIdent("db"), // TODO: parameterize
-
-				Decls: []ast.Decl{
-					&ast.GenDecl{
-						Tok: token.IMPORT,
-						Specs: []ast.Spec{
-							&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"database/sql"`}},
-							&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"errors"`}},
-							&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"fmt"`}},
-							&ast.ImportSpec{
-								Name: ast.NewIdent("."),
-								Path: &ast.BasicLit{Kind: token.STRING, Value: `"git.offline-twitter.com/offline-labs/gas-stack/pkg/db"`},
-							},
-							&ast.ImportSpec{
-								Name: ast.NewIdent("."),
-								Path: &ast.BasicLit{
-									Kind:  token.STRING,
-									Value: `"git.offline-twitter.com/offline-labs/gas-stack/pkg/flowutils"`,
-								},
+			decls := []ast.Decl{
+				&ast.GenDecl{
+					Tok: token.IMPORT,
+					Specs: []ast.Spec{
+						&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"database/sql"`}},
+						&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"errors"`}},
+						&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"fmt"`}},
+						&ast.ImportSpec{
+							Name: ast.NewIdent("."),
+							Path: &ast.BasicLit{Kind: token.STRING, Value: `"git.offline-twitter.com/offline-labs/gas-stack/pkg/db"`},
+						},
+						&ast.ImportSpec{
+							Name: ast.NewIdent("."),
+							Path: &ast.BasicLit{
+								Kind:  token.STRING,
+								Value: `"git.offline-twitter.com/offline-labs/gas-stack/pkg/flowutils"`,
 							},
 						},
 					},
-					modelgenerate.GenerateIDType(table),
-					modelgenerate.GenerateModelAST(table),
-					modelgenerate.GenerateSQLFieldsConst(table),
-					modelgenerate.GenerateSaveItemFunc(table),
-					modelgenerate.GenerateDeleteItemFunc(table),
-					modelgenerate.GenerateGetItemByIDFunc(table),
-					modelgenerate.GenerateGetAllItemsFunc(table),
 				},
 			}
+			if !table.IsWithoutRowid {
+				decls = append(decls, modelgenerate.GenerateIDType(table))
+			}
+			decls = append(decls,
+				modelgenerate.GenerateModelAST(table),
+				modelgenerate.GenerateSQLFieldsConst(table),
+				modelgenerate.GenerateSaveItemFunc(table),
+				modelgenerate.GenerateDeleteItemFunc(table),
+				modelgenerate.GenerateGetItemByIDFunc(table),
+				modelgenerate.GenerateGetAllItemsFunc(table),
+			)
 
-			PanicIf(printer.Fprint(os.Stdout, fset, file))
+			file := &ast.File{
+				Name:  ast.NewIdent("db"), // TODO: parameterize
+				Decls: decls,
+			}
+
+			PanicIf(modelgenerate.FprintWithComments(os.Stdout, file))
 		}
 
 		return nil

doc/TODO.txt

@@ -1,17 +1,31 @@
-TODO: auto-timestamps
-- SaveXyz should set created_at and updated_at; shouldn't touch is_deleted or deleted_at
+TODO: soft-deletion
+- enable soft-deletion if table has `is_deleted` and `deleted_at` fields
 - if soft delete is enabled, DeleteXyz should do update (not delete) and set is_deleted and deleted_at
     - ...and DeleteXyz should have pointer receiver for soft-delete
-- SaveXyz shouldn't set created_at in the do-update branch
 - GetXyzByID should include `ErrItemIsDeleted` if item is soft-deleted
 
-TODO: modified-timestamps
-- set updated_at and created_at in SaveXYZ
-- soft delete option
-
-TODO: generator-foreign-keys
-- add auto-foreign-key checking blocks to SaveXyz
-
 TODO: migration-structs
 - Right now, migrations are strings.  Could be a struct with "name", "up" and "down" fields
 - Adding a "down" operation enables handling newer DB versions with "down instead of error-out" for development (perhaps a flag)
+
+IDEA: migrations-table
+- Store migrations in a table.  This makes the schema more self-documenting.
+- Possible schema: name, sql_up, sql_down, hash (computed from those fields plus previous migration hash)
+    - or just rowid instead of hash?  Migration sequence should be immutable after publishing, so there should never be "conflicts"
+
+TODO: language-server-for-TODO.txt
+
+TODO: auto-migration-checker
+- Use `pkg/schema` to test whether a base schema plus a migration equals a new schema
+
+TODO: codegen SaveXyz update path doesn't check foreign keys
+- Insert path has FK error handling, but the update path wraps everything in Must
+- An update that violates an FK constraint will panic instead of returning an error
+
+TODO: codegen `without rowid` tables properly
+
+TODO: generated test file inclues global test DB setup, which is wrong
+
+TODO: join-tables
+- handle codegen for without rowid tables properly
+- add "get all "

go.mod

@@ -3,6 +3,7 @@ module git.offline-twitter.com/offline-labs/gas-stack
 go 1.22.5
 
 require (
+	github.com/go-test/deep v1.1.1
 	github.com/jinzhu/inflection v1.0.0
 	github.com/jmoiron/sqlx v1.4.0
 	github.com/mattn/go-sqlite3 v1.14.24

go.sum

@@ -5,6 +5,8 @@ github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/go-sql-driver/mysql v1.8.1 h1:LedoTUt/eveggdHS9qUFC1EFSa8bU2+1pZjSRpvNJ1Y=
 github.com/go-sql-driver/mysql v1.8.1/go.mod h1:wEBSXgmK//2ZFJyE+qWnIsVGmvmEKlqwuVSjsCm7DZg=
+github.com/go-test/deep v1.1.1 h1:0r/53hagsehfO4bzD2Pgr/+RgHqhmf+k1Bpse2cTu1U=
+github.com/go-test/deep v1.1.1/go.mod h1:5C2ZWiW0ErCdrYzpqxLbTX7MG14M9iiw8DgHncVwcsE=
 github.com/inconshreveable/mousetrap v1.1.0 h1:wN+x4NVGpMsO7ErUn/mUI3vEoE6Jt13X2s0bqwp9tc8=
 github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLfsEA9PFc4w1p2J65bw=
 github.com/jinzhu/inflection v1.0.0 h1:K317FqzuhWc8YvSVlFMCCUb36O/S9MCKRDI7QkRKD/E=

ops/devcontainer/Dockerfile

@@ -10,6 +10,8 @@ RUN apk add less
 RUN curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/master/install.sh | sh -s -- -b /usr/local/bin v2.0.2
 RUN GOBIN=/usr/local/bin go install git.offline-twitter.com/offline-labs/gocheckout@v0.0.2
 
+COPY etc/group /etc/group
+
 # Create a user in the container with the same UID as on the host machine, to avoid ownership conflicts.
 # The user gets sudo of course.
 #

ops/devcontainer/etc/group

@@ -0,0 +1,3 @@
+root:x:0:
+nogroup:x:65533:
+nobody:x:65534:

ops/devcontainer/start.sh

@@ -7,6 +7,7 @@ sudo docker run --rm -it \
     -v "$(go env GOMODCACHE):/gocache-vol/mod-cache" \
     -e GOMODCACHE=/gocache-vol/mod-cache \
     -e GOLANGCI_LINT_CACHE=/gocache-vol/lint-cache \
+    -v /memory:/memory \
     --workdir /code \
     --net host \
     gas

ops/gas_init_test.sh

@@ -9,7 +9,8 @@ set -e
 set -x
 
 PS4='+(${BASH_SOURCE}:${LINENO}): '
-cd "$(dirname "${BASH_SOURCE[0]}")/.."
+proj_root=$(readlink -f "$(dirname "${BASH_SOURCE[0]}")/..")
+cd "$proj_root"
 
 # Compile `gas`
 gas="/tmp/gas"
@@ -29,11 +30,19 @@ EOF
 
 cd $test_project
 
+# Add "replace" directive"
+echo "replace git.offline-twitter.com/offline-labs/gas-stack => $proj_root" >> go.mod
+
 # Create a new table in the schema
 cat >> pkg/db/schema.sql <<EOF
+create table item_flavor (rowid integer primary key, name text not null) strict;
+
 create table items (
     rowid integer primary key,
-    description text not null default ''
+    description text not null default '',
+    flavor integer references item_flavor(rowid),
+    created_at integer not null,
+    updated_at integer not null
 ) strict;
 EOF
 

pkg/codegen/modelgenerate/ast_helpers.go

@@ -0,0 +1,180 @@
+package modelgenerate
+
+import (
+	"bytes"
+	"go/ast"
+	"go/parser"
+	"go/printer"
+	"go/token"
+	"io"
+	"sort"
+)
+
+// These just need to be unique (i.e., something that will never be a real function in actual code).
+const (
+	commentMarker   = "__comment__jafkjewfkajwlekfjawlejf"
+	blankLineMarker = "__blank_line__awefjakwlefjkwalkefj"
+)
+
+// TrailingComments is a side map for attaching end-of-line comments to AST nodes.
+// Generators populate this map; FprintWithComments consumes and clears it.
+// For a regular statement, the comment appears at the end of the statement's line.
+// For a BlockStmt, the comment appears after the closing brace.
+//
+// This is a terrible implementation (global variable), but Node is an interface (pointer type),
+// so there's no risk of cross-contamination really.  Still bad for concurrent use, but hopefully
+// we don't have to do that.
+var TrailingComments = map[ast.Node]string{}
+
+// mustCall wraps a call expression in Must(...), producing AST for Must(inner).
+func mustCall(inner ast.Expr) *ast.CallExpr {
+	return &ast.CallExpr{
+		Fun:  ast.NewIdent("Must"),
+		Args: []ast.Expr{inner},
+	}
+}
+
+// Comment creates a marker statement that will be converted to a real Go comment
+// in the generated output by FprintWithComments.
+func Comment(text string) ast.Stmt {
+	return &ast.ExprStmt{X: &ast.CallExpr{
+		Fun:  ast.NewIdent(commentMarker),
+		Args: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: `"` + text + `"`}},
+	}}
+}
+
+// BlankLine creates a marker statement that will be converted to a blank line
+// in the generated output.  The marker occupies a line in the first-pass output;
+// when removed, the position gap causes the printer to insert a blank line.
+func BlankLine() *ast.ExprStmt {
+	return &ast.ExprStmt{X: &ast.CallExpr{
+		Fun: ast.NewIdent(blankLineMarker),
+	}}
+}
+
+// FprintWithComments prints an ast.File, converting Comment/BlankLine markers
+// into real Go comments and blank lines, preserving Doc comments, and applying
+// trailing comments from the TrailingComments side map.
+//
+// It does a round-trip (print -> parse -> modify -> print) to obtain real token
+// positions, which Go's comment system requires.
+func FprintWithComments(w io.Writer, file *ast.File) error {
+	// First pass: print to buffer
+	// Doc comments on FuncDecl/GenDecl are NOT added to file.Comments here;
+	// the printer handles them via setComment(d.Doc) when visiting each decl.
+	var buf bytes.Buffer
+	fset := token.NewFileSet()
+	if err := printer.Fprint(&buf, fset, file); err != nil {
+		return err
+	}
+
+	// Re-parse to get real positions (ParseComments preserves doc comments)
+	fset = token.NewFileSet()
+	parsed, err := parser.ParseFile(fset, "", buf.Bytes(), parser.ParseComments)
+	if err != nil {
+		return err
+	}
+
+	// Convert the tree-of-nodes into a slice-of-nodes
+	collectNodes := func(node ast.Node) []ast.Node {
+		var nodes []ast.Node
+		ast.Inspect(node, func(n ast.Node) bool {
+			// Filter out comments, as they only appear in the
+			switch n.(type) {
+			case *ast.CommentGroup, *ast.Comment:
+				return false
+			}
+			nodes = append(nodes, n)
+			return true
+		})
+		return nodes
+	}
+
+	// Parallel walk: apply TrailingComments from the side map.
+	// Both trees have identical structure (the reparse is just a positioned copy),
+	// so ast.Inspect visits nodes in the same order.  We skip comment nodes to
+	// avoid mismatches from Doc fields.
+	if len(TrailingComments) > 0 {
+		origNodes := collectNodes(file)
+		reparsedNodes := collectNodes(parsed)
+		for i, orig := range origNodes {
+			text, ok := TrailingComments[orig]
+			if !ok {
+				continue
+			}
+			reparsed := reparsedNodes[i]
+			parsed.Comments = append(parsed.Comments, &ast.CommentGroup{
+				List: []*ast.Comment{{Slash: reparsed.End(), Text: "// " + text}},
+			})
+		}
+	}
+
+	extractCommentMarker := func(stmt ast.Stmt) (string, bool) {
+		expr, ok := stmt.(*ast.ExprStmt)
+		if !ok {
+			return "", false
+		}
+		call, ok := expr.X.(*ast.CallExpr)
+		if !ok {
+			return "", false
+		}
+		ident, ok := call.Fun.(*ast.Ident)
+		if !ok || ident.Name != commentMarker {
+			return "", false
+		}
+		lit := call.Args[0].(*ast.BasicLit)
+		return lit.Value[1 : len(lit.Value)-1], true
+	}
+
+	isBlankLineMarker := func(stmt ast.Stmt) bool {
+		expr, ok := stmt.(*ast.ExprStmt)
+		if !ok {
+			return false
+		}
+		call, ok := expr.X.(*ast.CallExpr)
+		if !ok {
+			return false
+		}
+		ident, ok := call.Fun.(*ast.Ident)
+		return ok && ident.Name == blankLineMarker
+	}
+
+	// Convert comment and blank-line markers
+	ast.Inspect(parsed, func(n ast.Node) bool {
+		// We only care about Block nodes
+		block, ok := n.(*ast.BlockStmt)
+		if !ok {
+			return true
+		}
+
+		// Check the statements in this block , replacing our artificial Comment(...) and BlankLine(...) nodes
+		// in the block statement's body with actual ones
+		filtered := block.List[:0]
+		for _, stmt := range block.List {
+			if text, ok := extractCommentMarker(stmt); ok {
+				// If it's a comment, add it to the fileset's list of Comments
+				parsed.Comments = append(parsed.Comments, &ast.CommentGroup{
+					List: []*ast.Comment{{Slash: stmt.Pos(), Text: "// " + text}},
+				})
+			} else if isBlankLineMarker(stmt) {
+				// If it's a blank line, just remove it; the position gap creates a blank line
+			} else {
+				// Otherwise: it's a normal statement, so keep it.
+				filtered = append(filtered, stmt)
+			}
+		}
+		block.List = filtered
+		return true
+	})
+
+	sort.Slice(parsed.Comments, func(i, j int) bool {
+		return parsed.Comments[i].Pos() < parsed.Comments[j].Pos()
+	})
+
+	// Clear side map for next invocation
+	for k := range TrailingComments {
+		delete(TrailingComments, k)
+	}
+
+	return printer.Fprint(w, fset, parsed)
+}

pkg/codegen/modelgenerate/generate_model.go

@@ -13,6 +13,25 @@ import (
 	"git.offline-twitter.com/offline-labs/gas-stack/pkg/textutils"
 )
 
+// ---------------
+// Helpers
+// ---------------
+
+var (
+	dbRecv    = &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent("db")}, Type: ast.NewIdent("DB")}}}
+	dbDB      = &ast.SelectorExpr{X: ast.NewIdent("db"), Sel: ast.NewIdent("DB")}
+	fmtErrorf = &ast.SelectorExpr{X: ast.NewIdent("fmt"), Sel: ast.NewIdent("Errorf")}
+)
+
+func SQLFieldsConstIdent(tbl schema.Table) *ast.Ident {
+	return ast.NewIdent(strings.ToLower(tbl.GoTypeName) + "SQLFields")
+}
+
+// ---------------
+// Generators
+// ---------------
+
+// GenerateIDType produces an AST for the model's ID field.
 func GenerateIDType(table schema.Table) *ast.GenDecl {
 	// e.g., `type FoodID int`
 	return &ast.GenDecl{
@@ -37,33 +56,14 @@ func GenerateModelAST(table schema.Table) *ast.GenDecl {
 				Tag:   &ast.BasicLit{Kind: token.STRING, Value: "`db:\"rowid\" json:\"id\"`"},
 			})
 		default:
-			if col.IsForeignKey && strings.HasSuffix(col.Name, "_id") {
+			if col.IsNonCodeTableForeignKey() {
 				fields = append(fields, &ast.Field{
-					Names: []*ast.Ident{ast.NewIdent(textutils.SnakeToCamel(strings.TrimSuffix(col.Name, "_id")) + "ID")},
+					Names: []*ast.Ident{ast.NewIdent(col.GoFieldName())},
 					Type:  ast.NewIdent(schema.TypenameFromTablename(col.ForeignKeyTargetTable) + "ID"),
 					Tag:   &ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("`db:\"%s\" json:\"%s\"`", col.Name, col.Name)},
 				})
 			} else {
-				typeName := "string"
-				switch col.Type {
-				case "integer", "int":
-					if strings.HasPrefix(col.Name, "is_") || strings.HasPrefix(col.Name, "has_") {
-						typeName = "bool"
-					} else if strings.HasSuffix(col.Name, "_at") {
-						typeName = "Timestamp"
-					} else {
-						typeName = "int64"
-					}
-				case "text":
-					typeName = "string"
-				case "real":
-					typeName = "float32"
-				case "blob":
-					typeName = "[]byte"
-				default:
-					panic("Unrecognized sqlite column type: " + col.Type)
-				}
-
+				typeName := col.GoType()
 				fields = append(fields, &ast.Field{
 					Names: []*ast.Ident{ast.NewIdent(textutils.SnakeToCamel(col.Name))},
 					Type:  ast.NewIdent(typeName),
@@ -82,6 +82,129 @@ func GenerateModelAST(table schema.Table) *ast.GenDecl {
 	}
 }
 
+// buildFKCheckLambda builds the `checkForeignKeyFailures := func(err error) error { ... }` AST.
+// Returns the assignment statement and whether any FK columns were found.
+func buildFKCheckLambda(tbl schema.Table) (*ast.AssignStmt, bool) {
+	hasFks := false
+	stmt := &ast.AssignStmt{
+		Lhs: []ast.Expr{ast.NewIdent("checkForeignKeyFailures")},
+		Tok: token.DEFINE,
+		Rhs: []ast.Expr{
+			&ast.FuncLit{
+				Type: &ast.FuncType{
+					Params: &ast.FieldList{
+						List: []*ast.Field{{
+							Names: []*ast.Ident{ast.NewIdent("err")},
+							Type:  ast.NewIdent("error"),
+						}},
+					},
+					Results: &ast.FieldList{
+						List: []*ast.Field{{Type: ast.NewIdent("error")}},
+					},
+				},
+				Body: &ast.BlockStmt{
+					List: func() []ast.Stmt {
+						ret := []ast.Stmt{}
+						// if !isSqliteFkError(err) { return nil }
+						ret = append(ret, &ast.IfStmt{
+							Cond: &ast.UnaryExpr{Op: token.NOT, X: &ast.CallExpr{Fun: ast.NewIdent("IsSqliteFkError"), Args: []ast.Expr{ast.NewIdent("err")}}},
+							Body: &ast.BlockStmt{List: []ast.Stmt{&ast.ReturnStmt{Results: []ast.Expr{ast.NewIdent("nil")}}}},
+						})
+
+						for _, col := range tbl.Columns {
+							if !col.IsForeignKey { // Check both "real" foreign keys and code table values
+								continue
+							}
+							hasFks = true
+
+							structFieldName := col.GoFieldName()
+							structField := &ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent(structFieldName)}
+
+							if col.IsNonCodeTableForeignKey() {
+								// Real foreign key; look up referent by ID to see if it exists
+								ret = append(ret, &ast.IfStmt{
+									Init: &ast.AssignStmt{
+										Lhs: []ast.Expr{ast.NewIdent("_"), ast.NewIdent("err")},
+										Tok: token.DEFINE,
+										Rhs: []ast.Expr{
+											&ast.CallExpr{
+												Fun:  &ast.SelectorExpr{X: ast.NewIdent("db"), Sel: ast.NewIdent(getByIDFuncName(col.ForeignKeyTargetTable))},
+												Args: []ast.Expr{structField},
+											},
+										},
+									},
+									Cond: &ast.CallExpr{
+										Fun:  &ast.SelectorExpr{X: ast.NewIdent("errors"), Sel: ast.NewIdent("Is")},
+										Args: []ast.Expr{ast.NewIdent("err"), ast.NewIdent("ErrNotInDB")},
+									},
+									Body: &ast.BlockStmt{
+										List: []ast.Stmt{
+											&ast.ReturnStmt{
+												Results: []ast.Expr{
+													&ast.CallExpr{
+														Fun: ast.NewIdent("NewForeignKeyError"),
+														Args: []ast.Expr{
+															&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("%q", structFieldName)},
+															&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("%q", col.ForeignKeyTargetTable)},
+															structField,
+														},
+													},
+												},
+											},
+										},
+									},
+								})
+							} else {
+								// Code table value.  Query the table to see if it exists
+								ret = append(ret, &ast.IfStmt{
+									Init: &ast.AssignStmt{
+										Lhs: []ast.Expr{ast.NewIdent("err")},
+										Tok: token.ASSIGN,
+										Rhs: []ast.Expr{
+											&ast.CallExpr{
+												Fun: &ast.SelectorExpr{X: dbDB, Sel: ast.NewIdent("Get")},
+												Args: []ast.Expr{
+													&ast.CallExpr{Fun: ast.NewIdent("new"), Args: []ast.Expr{ast.NewIdent("int")}},
+													&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("`select 1 from %s where rowid = ?`", col.ForeignKeyTargetTable)},
+													structField,
+												},
+											},
+										},
+									},
+									Cond: &ast.CallExpr{
+										Fun:  &ast.SelectorExpr{X: ast.NewIdent("errors"), Sel: ast.NewIdent("Is")},
+										Args: []ast.Expr{ast.NewIdent("err"), &ast.SelectorExpr{X: ast.NewIdent("sql"), Sel: ast.NewIdent("ErrNoRows")}},
+									},
+									Body: &ast.BlockStmt{
+										List: []ast.Stmt{
+											&ast.ReturnStmt{
+												Results: []ast.Expr{
+													&ast.CallExpr{
+														Fun: ast.NewIdent("NewForeignKeyError"),
+														Args: []ast.Expr{
+															&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("%q", structFieldName)},
+															ast.NewIdent(fmt.Sprintf("%q", col.ForeignKeyTargetTable)),
+															structField,
+														},
+													},
+												},
+											},
+										},
+									},
+								})
+							}
+						}
+						// final return nil
+						ret = append(ret, &ast.ReturnStmt{Results: []ast.Expr{ast.NewIdent("nil")}})
+						return ret
+					}(),
+				},
+			},
+		},
+	}
+	return stmt, hasFks
+}
+
 // GenerateSaveItemFunc produces an AST for the SaveXyz() function of the model.
 // E.g., a table with `table.TypeName = "foods"` will produce a "SaveFood()" function.
 func GenerateSaveItemFunc(tbl schema.Table) *ast.FuncDecl {
@@ -89,6 +212,9 @@ func GenerateSaveItemFunc(tbl schema.Table) *ast.FuncDecl {
 	insertVals := make([]string, 0, len(tbl.Columns))
 	updatePairs := make([]string, 0, len(tbl.Columns))
 
+	hasCreatedAt, hasUpdatedAt := tbl.HasAutoTimestamps()
+
+	// Assemble data for building SQL "insert" and "update" strings
 	for _, col := range tbl.Columns {
 		if col.Name == "rowid" {
 			continue
@@ -99,104 +225,200 @@ func GenerateSaveItemFunc(tbl schema.Table) *ast.FuncDecl {
 			val = fmt.Sprintf("nullif(%s, 0)", val)
 		}
 		insertVals = append(insertVals, val)
+		// created_at should not be updated after creation
+		if col.Name == "created_at" && hasCreatedAt {
+			continue
+		}
 		updatePairs = append(updatePairs, col.Name+"="+val)
 	}
-
-	insertStmt := fmt.Sprintf("\n\t\t    insert into %s (%s)\n\t\t          values (%s)\n\t\t", tbl.TableName, strings.Join(insertCols, ", "), strings.Join(insertVals, ", "))
+	insertStmt := fmt.Sprintf("\n\t\t    insert into %s (%s)\n\t\t         values (%s)\n\t\t", tbl.TableName, strings.Join(insertCols, ", "), strings.Join(insertVals, ", "))
 	updateStmt := fmt.Sprintf("\n\t\t    update %s\n\t\t       set %s\n\t\t     where rowid = :rowid\n\t\t", tbl.TableName, strings.Join(updatePairs, ",\n\t\t           "))
 
+	checkForeignKeyFailuresAssignment, hasFks := buildFKCheckLambda(tbl)
+
 	funcBody := &ast.BlockStmt{
-		List: []ast.Stmt{
-			&ast.IfStmt{
+		List: func() []ast.Stmt {
+			ret := []ast.Stmt{}
+			if hasFks {
+				ret = append(ret, checkForeignKeyFailuresAssignment, BlankLine())
+			}
+			if hasUpdatedAt {
+				// Auto-timestamps: updated_at
+				ret = append(ret, &ast.AssignStmt{
+					Lhs: []ast.Expr{&ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("UpdatedAt")}},
+					Tok: token.ASSIGN,
+					Rhs: []ast.Expr{&ast.CallExpr{Fun: ast.NewIdent("TimestampNow"), Args: []ast.Expr{}}},
+				})
+			}
+			// if item.ID == 0 {...} else {...}
+			ret = append(ret, &ast.IfStmt{
 				Cond: &ast.BinaryExpr{
 					X:  &ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")},
 					Op: token.EQL,
 					Y:  &ast.BasicLit{Kind: token.INT, Value: "0"},
 				},
 				Body: &ast.BlockStmt{
-					List: []ast.Stmt{
-						&ast.AssignStmt{
-							Lhs: []ast.Expr{ast.NewIdent("result")},
-							Tok: token.DEFINE,
-							Rhs: []ast.Expr{&ast.CallExpr{
-								Fun: ast.NewIdent("Must"),
-								Args: []ast.Expr{&ast.CallExpr{
-									Fun: &ast.SelectorExpr{X: ast.NewIdent("db.DB"), Sel: ast.NewIdent("NamedExec")},
-									Args: []ast.Expr{
-										&ast.BasicLit{Kind: token.STRING, Value: "`" + insertStmt + "`"},
-										ast.NewIdent(tbl.VarName),
+					// Do create
+					List: append(
+						func() []ast.Stmt {
+							ret1 := []ast.Stmt{Comment("Do create")}
+							if hasCreatedAt {
+								// Auto-timestamps: created_at
+								ret1 = append(ret1, &ast.AssignStmt{
+									Lhs: []ast.Expr{&ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("CreatedAt")}},
+									Tok: token.ASSIGN,
+									Rhs: []ast.Expr{&ast.CallExpr{Fun: ast.NewIdent("TimestampNow"), Args: []ast.Expr{}}},
+								})
+							}
+							namedExecStmt := &ast.CallExpr{
+								Fun: &ast.SelectorExpr{X: dbDB, Sel: ast.NewIdent("NamedExec")},
+								Args: []ast.Expr{
+									&ast.BasicLit{Kind: token.STRING, Value: "`" + insertStmt + "`"},
+									ast.NewIdent(tbl.VarName),
+								},
+							}
+							if !hasFks {
+								// No foreign key checking needed; just use `Must` for brevity
+								return append(ret1, &ast.AssignStmt{
+									Lhs: []ast.Expr{ast.NewIdent("result")},
+									Tok: token.DEFINE,
+									Rhs: []ast.Expr{mustCall(namedExecStmt)},
+								})
+							}
+
+							return append(ret1,
+								// result, err := db.DB.NamedExec(`...`, u)
+								&ast.AssignStmt{
+									Lhs: []ast.Expr{
+										ast.NewIdent("result"),
+										ast.NewIdent("err"),
 									},
-								}},
-							}},
-						},
+									Tok: token.DEFINE,
+									Rhs: []ast.Expr{namedExecStmt},
+								},
+
+								// if fkErr := checkForeignKeyFailures(err); fkErr != nil { return fkErr } else if err != nil { panic(err) }
+								&ast.IfStmt{
+									Init: &ast.AssignStmt{
+										Lhs: []ast.Expr{ast.NewIdent("fkErr")},
+										Tok: token.DEFINE,
+										Rhs: []ast.Expr{
+											&ast.CallExpr{
+												Fun:  ast.NewIdent("checkForeignKeyFailures"),
+												Args: []ast.Expr{ast.NewIdent("err")},
+											},
+										},
+									},
+									Cond: &ast.BinaryExpr{
+										X:  ast.NewIdent("fkErr"),
+										Op: token.NEQ,
+										Y:  ast.NewIdent("nil"),
+									},
+									Body: &ast.BlockStmt{
+										List: []ast.Stmt{
+											&ast.ReturnStmt{
+												Results: []ast.Expr{ast.NewIdent("fkErr")},
+											},
+										},
+									},
+									Else: func() *ast.IfStmt {
+										panicStmt := &ast.ExprStmt{
+											X: &ast.CallExpr{
+												Fun:  ast.NewIdent("panic"),
+												Args: []ast.Expr{ast.NewIdent("err")},
+											},
+										}
+										TrailingComments[panicStmt] = "not a foreign key error"
+										return &ast.IfStmt{
+											Cond: &ast.BinaryExpr{
+												X:  ast.NewIdent("err"),
+												Op: token.NEQ,
+												Y:  ast.NewIdent("nil"),
+											},
+											Body: &ast.BlockStmt{
+												List: []ast.Stmt{panicStmt},
+											},
+										}
+									}(),
+								},
+							)
+						}(),
 						&ast.AssignStmt{
 							Lhs: []ast.Expr{&ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")}},
 							Tok: token.ASSIGN,
 							Rhs: []ast.Expr{&ast.CallExpr{
 								Fun: ast.NewIdent(tbl.TypeIDName),
-								Args: []ast.Expr{&ast.CallExpr{
-									Fun: ast.NewIdent("Must"),
-									Args: []ast.Expr{&ast.CallExpr{
-										Fun:  &ast.SelectorExpr{X: ast.NewIdent("result"), Sel: ast.NewIdent("LastInsertId")},
-										Args: []ast.Expr{},
-									}},
-								}},
+								Args: []ast.Expr{mustCall(&ast.CallExpr{
+									Fun:  &ast.SelectorExpr{X: ast.NewIdent("result"), Sel: ast.NewIdent("LastInsertId")},
+									Args: []ast.Expr{},
+								})},
 							}},
 						},
-					},
+					),
 				},
 				Else: &ast.BlockStmt{
+					// Do update
 					List: []ast.Stmt{
+						Comment("Do update"),
 						&ast.AssignStmt{
 							Lhs: []ast.Expr{ast.NewIdent("result")},
 							Tok: token.DEFINE,
-							Rhs: []ast.Expr{&ast.CallExpr{
-								Fun: ast.NewIdent("Must"),
-								Args: []ast.Expr{&ast.CallExpr{
-									Fun:  &ast.SelectorExpr{X: ast.NewIdent("db.DB"), Sel: ast.NewIdent("NamedExec")},
-									Args: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: "`" + updateStmt + "`"}, ast.NewIdent(tbl.VarName)},
-								}},
-							}},
+							Rhs: []ast.Expr{mustCall(&ast.CallExpr{
+								Fun:  &ast.SelectorExpr{X: dbDB, Sel: ast.NewIdent("NamedExec")},
+								Args: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: "`" + updateStmt + "`"}, ast.NewIdent(tbl.VarName)},
+							})},
 						},
 
 						&ast.IfStmt{
 							Cond: &ast.BinaryExpr{
-								X: &ast.CallExpr{
-									Fun: ast.NewIdent("Must"),
-									Args: []ast.Expr{&ast.CallExpr{
-										Fun:  &ast.SelectorExpr{X: ast.NewIdent("result"), Sel: ast.NewIdent("RowsAffected")},
-										Args: []ast.Expr{},
-									}},
-								},
+								X: mustCall(&ast.CallExpr{
+									Fun:  &ast.SelectorExpr{X: ast.NewIdent("result"), Sel: ast.NewIdent("RowsAffected")},
+									Args: []ast.Expr{},
+								}),
 								Op: token.NEQ,
 								Y:  &ast.BasicLit{Kind: token.INT, Value: "1"},
 							},
-							Body: &ast.BlockStmt{List: []ast.Stmt{&ast.ExprStmt{X: &ast.CallExpr{Fun: ast.NewIdent("panic"), Args: []ast.Expr{&ast.CallExpr{Fun: ast.NewIdent("fmt.Errorf"), Args: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("\"got %s with ID (%%d), so attempted update, but it doesn't exist\"", strings.ToLower(tbl.GoTypeName))}, &ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")}}}}}}}},
+							Body: &ast.BlockStmt{List: []ast.Stmt{&ast.ExprStmt{X: &ast.CallExpr{Fun: ast.NewIdent("panic"), Args: []ast.Expr{&ast.CallExpr{Fun: fmtErrorf, Args: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("\"got %s with ID (%%d), so attempted update, but it doesn't exist\"", strings.ToLower(tbl.GoTypeName))}, &ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")}}}}}}}},
 						},
 					},
 				},
-			},
-		},
+			})
+			if hasFks {
+				// If there's foreign key checking, it needs to return an error (or nil)
+				ret = append(ret, &ast.ReturnStmt{Results: []ast.Expr{ast.NewIdent("nil")}})
+			}
+			return ret
+		}(),
 	}
 
 	funcDecl := &ast.FuncDecl{
-		Recv: &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent("db")}, Type: ast.NewIdent("DB")}}},
+		Doc: &ast.CommentGroup{List: []*ast.Comment{
+			{Text: fmt.Sprintf("// Save%s creates or updates a %s in the database.", tbl.GoTypeName, tbl.GoTypeName)},
+			{Text: "// If the item doesn't exist (has no ID set), it will create it; otherwise it will do an update."},
+		}},
+		Recv: dbRecv,
 		Name: ast.NewIdent("Save" + tbl.GoTypeName),
 		Type: &ast.FuncType{
-			Params:  &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent(tbl.VarName)}, Type: &ast.StarExpr{X: ast.NewIdent(tbl.GoTypeName)}}}},
-			Results: nil,
+			Params: &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent(tbl.VarName)}, Type: &ast.StarExpr{X: ast.NewIdent(tbl.GoTypeName)}}}},
+			Results: func() *ast.FieldList {
+				if hasFks {
+					return &ast.FieldList{List: []*ast.Field{{Type: ast.NewIdent("error")}}}
+				}
+				return nil
+			}(),
 		},
 		Body: funcBody,
 	}
 	return funcDecl
 }
 
+func getByIDFuncName(tblname string) string {
+	return "Get" + schema.TypenameFromTablename(tblname) + "ByID"
+}
+
 // GenerateGetItemByIDFunc produces an AST for the `GetXyzByID()` function.
 // E.g., a table with `table.TypeName = "foods"` will produce a "GetFoodByID()" function.
 func GenerateGetItemByIDFunc(tbl schema.Table) *ast.FuncDecl {
-	funcName := "Get" + tbl.GoTypeName + "ByID"
-
-	recv := &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent("db")}, Type: ast.NewIdent("DB")}}}
 	arg := &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent("id")}, Type: ast.NewIdent(tbl.TypeIDName)}}}
 	result := &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent("ret")}, Type: ast.NewIdent(tbl.GoTypeName)}, {Names: []*ast.Ident{ast.NewIdent("err")}, Type: ast.NewIdent("error")}}}
 
@@ -216,7 +438,7 @@ func GenerateGetItemByIDFunc(tbl schema.Table) *ast.FuncDecl {
 			&ast.AssignStmt{
 				Lhs: []ast.Expr{ast.NewIdent("err")},
 				Tok: token.ASSIGN,
-				Rhs: []ast.Expr{&ast.CallExpr{Fun: &ast.SelectorExpr{X: ast.NewIdent("db.DB"), Sel: ast.NewIdent("Get")}, Args: []ast.Expr{&ast.UnaryExpr{Op: token.AND, X: ast.NewIdent("ret")}, selectExpr, ast.NewIdent("id")}}},
+				Rhs: []ast.Expr{&ast.CallExpr{Fun: &ast.SelectorExpr{X: dbDB, Sel: ast.NewIdent("Get")}, Args: []ast.Expr{&ast.UnaryExpr{Op: token.AND, X: ast.NewIdent("ret")}, selectExpr, ast.NewIdent("id")}}},
 			},
 			&ast.IfStmt{
 				Cond: &ast.CallExpr{Fun: &ast.SelectorExpr{X: ast.NewIdent("errors"), Sel: ast.NewIdent("Is")}, Args: []ast.Expr{ast.NewIdent("err"), &ast.SelectorExpr{X: ast.NewIdent("sql"), Sel: ast.NewIdent("ErrNoRows")}}},
@@ -227,8 +449,8 @@ func GenerateGetItemByIDFunc(tbl schema.Table) *ast.FuncDecl {
 	}
 
 	funcDecl := &ast.FuncDecl{
-		Recv: recv,
-		Name: ast.NewIdent(funcName),
+		Recv: dbRecv,
+		Name: ast.NewIdent(getByIDFuncName(tbl.TableName)),
 		Type: &ast.FuncType{Params: arg, Results: result},
 		Body: funcBody,
 	}
@@ -239,9 +461,6 @@ func GenerateGetItemByIDFunc(tbl schema.Table) *ast.FuncDecl {
 // E.g., a table with `table.TypeName = "foods"` will produce a "GetAllFoods()" function.
 func GenerateGetAllItemsFunc(tbl schema.Table) *ast.FuncDecl {
 	funcName := "GetAll" + inflection.Plural(tbl.GoTypeName)
-	recv := &ast.FieldList{List: []*ast.Field{
-		{Names: []*ast.Ident{ast.NewIdent("db")}, Type: ast.NewIdent("DB")},
-	}}
 	result := &ast.FieldList{List: []*ast.Field{
 		{Names: []*ast.Ident{ast.NewIdent("ret")}, Type: &ast.ArrayType{Elt: ast.NewIdent(tbl.GoTypeName)}},
 	}}
@@ -251,19 +470,19 @@ func GenerateGetAllItemsFunc(tbl schema.Table) *ast.FuncDecl {
 		Args: []ast.Expr{
 			&ast.CallExpr{
 				Fun: &ast.SelectorExpr{
-					X:   ast.NewIdent("db.DB"),
+					X:   dbDB,
 					Sel: ast.NewIdent("Select"),
 				},
 				Args: []ast.Expr{
 					&ast.UnaryExpr{Op: token.AND, X: ast.NewIdent("ret")},
 					&ast.BinaryExpr{
 						X: &ast.BinaryExpr{
-							X:  &ast.BasicLit{Kind: token.STRING, Value: "`SELECT `"},
+							X:  &ast.BasicLit{Kind: token.STRING, Value: "`select `"},
 							Op: token.ADD,
 							Y:  SQLFieldsConstIdent(tbl),
 						},
 						Op: token.ADD,
-						Y:  &ast.BasicLit{Kind: token.STRING, Value: "` FROM " + tbl.TableName + "`"},
+						Y:  &ast.BasicLit{Kind: token.STRING, Value: "` from " + tbl.TableName + "`"},
 					},
 				},
 			},
@@ -278,7 +497,7 @@ func GenerateGetAllItemsFunc(tbl schema.Table) *ast.FuncDecl {
 	}
 
 	return &ast.FuncDecl{
-		Recv: recv,
+		Recv: dbRecv,
 		Name: ast.NewIdent(funcName),
 		Type: &ast.FuncType{
 			Params:  &ast.FieldList{},
@@ -291,34 +510,29 @@ func GenerateGetAllItemsFunc(tbl schema.Table) *ast.FuncDecl {
 // GenerateDeleteItemFunc produces an AST for the `DeleteXyz()` function.
 // E.g., a table with `table.TypeName = "foods"` will produce a "DeleteFood()" function.
 func GenerateDeleteItemFunc(tbl schema.Table) *ast.FuncDecl {
-	funcName := "Delete" + tbl.GoTypeName
-	recv := &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent("db")}, Type: ast.NewIdent("DB")}}}
-	arg := &ast.FieldList{List: []*ast.Field{{Names: []*ast.Ident{ast.NewIdent(tbl.VarName)}, Type: ast.NewIdent(tbl.GoTypeName)}}}
+	arg := &ast.FieldList{List: []*ast.Field{{
+		Names: []*ast.Ident{ast.NewIdent(tbl.VarName)},
+		Type:  ast.NewIdent(tbl.GoTypeName),
+	}}}
 
 	funcBody := &ast.BlockStmt{
 		List: []ast.Stmt{
 			&ast.AssignStmt{
 				Lhs: []ast.Expr{ast.NewIdent("result")},
 				Tok: token.DEFINE,
-				Rhs: []ast.Expr{&ast.CallExpr{
-					Fun: ast.NewIdent("Must"),
-					Args: []ast.Expr{&ast.CallExpr{
-						Fun: &ast.SelectorExpr{X: ast.NewIdent("db.DB"), Sel: ast.NewIdent("Exec")},
-						Args: []ast.Expr{
-							&ast.BasicLit{Kind: token.STRING, Value: "`delete from " + tbl.TableName + " where rowid = ?`"},
-							&ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")},
-						},
-					}},
-				}},
+				Rhs: []ast.Expr{mustCall(&ast.CallExpr{
+					Fun: &ast.SelectorExpr{X: dbDB, Sel: ast.NewIdent("Exec")},
+					Args: []ast.Expr{
+						&ast.BasicLit{Kind: token.STRING, Value: "`delete from " + tbl.TableName + " where rowid = ?`"},
+						&ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")},
+					},
+				})},
 			},
 			&ast.IfStmt{
 				Cond: &ast.BinaryExpr{
-					X: &ast.CallExpr{
-						Fun: ast.NewIdent("Must"),
-						Args: []ast.Expr{
-							&ast.CallExpr{Fun: &ast.SelectorExpr{X: ast.NewIdent("result"), Sel: ast.NewIdent("RowsAffected")}, Args: []ast.Expr{}},
-						},
-					},
+					X: mustCall(
+						&ast.CallExpr{Fun: &ast.SelectorExpr{X: ast.NewIdent("result"), Sel: ast.NewIdent("RowsAffected")}, Args: []ast.Expr{}},
+					),
 					Op: token.NEQ,
 					Y:  &ast.BasicLit{Kind: token.INT, Value: "1"},
 				},
@@ -326,7 +540,7 @@ func GenerateDeleteItemFunc(tbl schema.Table) *ast.FuncDecl {
 					&ast.ExprStmt{X: &ast.CallExpr{
 						Fun: ast.NewIdent("panic"),
 						Args: []ast.Expr{&ast.CallExpr{
-							Fun: ast.NewIdent("fmt.Errorf"),
+							Fun: fmtErrorf,
 							Args: []ast.Expr{
 								&ast.BasicLit{Kind: token.STRING, Value: fmt.Sprintf("\"tried to delete %s with ID (%%d) but it doesn't exist\"", strings.ToLower(tbl.GoTypeName))},
 								&ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent("ID")},
@@ -339,8 +553,8 @@ func GenerateDeleteItemFunc(tbl schema.Table) *ast.FuncDecl {
 	}
 
 	funcDecl := &ast.FuncDecl{
-		Recv: recv,
-		Name: ast.NewIdent(funcName),
+		Recv: dbRecv,
+		Name: ast.NewIdent("Delete" + tbl.GoTypeName),
 		Type: &ast.FuncType{Params: arg, Results: nil},
 		Body: funcBody,
 	}
@@ -351,7 +565,11 @@ func GenerateDeleteItemFunc(tbl schema.Table) *ast.FuncDecl {
 func GenerateSQLFieldsConst(tbl schema.Table) *ast.GenDecl {
 	columns := make([]string, 0, len(tbl.Columns))
 	for _, col := range tbl.Columns {
-		columns = append(columns, col.Name)
+		if col.IsNullableForeignKey() {
+			columns = append(columns, fmt.Sprintf("ifnull(%s, 0) %s", col.Name, col.Name))
+		} else {
+			columns = append(columns, col.Name)
+		}
 	}
 	// Join with comma and space
 	value := "`" + strings.Join(columns, ", ") + "`"
@@ -366,11 +584,3 @@ func GenerateSQLFieldsConst(tbl schema.Table) *ast.GenDecl {
 		},
 	}
 }
-
-// ---------------
-// Helpers
-// ---------------
-
-func SQLFieldsConstIdent(tbl schema.Table) *ast.Ident {
-	return ast.NewIdent(strings.ToLower(tbl.GoTypeName) + "SQLFields")
-}

pkg/codegen/modelgenerate/generate_testfile.go

@@ -15,69 +15,25 @@ func GenerateModelTestAST(tbl schema.Table, gomodName string) *ast.File {
 	packageName := "db"
 	testpackageName := packageName + "_test"
 
-	testDBDecl := &ast.GenDecl{
-		Tok: token.VAR,
-		Specs: []ast.Spec{
-			&ast.ValueSpec{
-				Names: []*ast.Ident{ast.NewIdent("TestDB")},
-				Type:  &ast.StarExpr{X: ast.NewIdent("DB")},
-			},
-		},
-	}
-
-	initFuncDecl := &ast.FuncDecl{
-		Name: ast.NewIdent("init"),
-		Type: &ast.FuncType{Params: &ast.FieldList{}},
-		Body: &ast.BlockStmt{
-			List: []ast.Stmt{
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{ast.NewIdent("TestDB")},
-					Tok: token.ASSIGN,
-					Rhs: []ast.Expr{&ast.CallExpr{
-						Fun:  ast.NewIdent("MakeDB"),
-						Args: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: `"tmp"`}},
-					}},
-				},
-			},
-		},
-	}
-
-	makeDBHelperDecl := &ast.FuncDecl{
-		Name: ast.NewIdent("MakeDB"),
+	// func MakeItem() Item { return Item{} }
+	makeItemFunc := &ast.FuncDecl{
+		Name: ast.NewIdent("Make" + tbl.GoTypeName),
 		Type: &ast.FuncType{
-			Params: &ast.FieldList{
-				List: []*ast.Field{{
-					Names: []*ast.Ident{ast.NewIdent("dbName")},
-					Type:  ast.NewIdent("string"),
-				}},
-			},
+			Params: &ast.FieldList{},
 			Results: &ast.FieldList{
-				List: []*ast.Field{{Type: &ast.StarExpr{X: ast.NewIdent("DB")}}},
+				List: []*ast.Field{
+					{Type: ast.NewIdent(tbl.GoTypeName)},
+				},
 			},
 		},
 		Body: &ast.BlockStmt{
 			List: []ast.Stmt{
-				// db := Must(Create(fmt.Sprintf("file:%s?mode=memory&cache=shared", dbName)))
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{ast.NewIdent("db")},
-					Tok: token.DEFINE,
-					Rhs: []ast.Expr{&ast.CallExpr{
-						Fun: ast.NewIdent("Must"),
-						Args: []ast.Expr{&ast.CallExpr{
-							Fun: ast.NewIdent("Create"),
-							Args: []ast.Expr{&ast.CallExpr{
-								Fun: ast.NewIdent("fmt.Sprintf"),
-								Args: []ast.Expr{
-									&ast.BasicLit{Kind: token.STRING, Value: `"file:%s?mode=memory&cache=shared"`},
-									ast.NewIdent("dbName"),
-								},
-							}},
-						}},
-					}},
-				},
-				// return db
 				&ast.ReturnStmt{
-					Results: []ast.Expr{ast.NewIdent("db")},
+					Results: []ast.Expr{
+						&ast.CompositeLit{
+							Type: ast.NewIdent(tbl.GoTypeName),
+						},
+					},
 				},
 			},
 		},
@@ -89,138 +45,157 @@ func GenerateModelTestAST(tbl schema.Table, gomodName string) *ast.File {
 	description1 := `"an item"`
 	description2 := `"a big item"`
 
+	hasCreatedAt, hasUpdatedAt := tbl.HasAutoTimestamps()
+
+	testFuncType := &ast.FuncType{
+		Params: &ast.FieldList{
+			List: []*ast.Field{{
+				Names: []*ast.Ident{ast.NewIdent("t")},
+				Type:  &ast.StarExpr{X: &ast.SelectorExpr{X: ast.NewIdent("testing"), Sel: ast.NewIdent("T")}},
+			}},
+		},
+	}
+
 	testCreateUpdateDelete := &ast.FuncDecl{
 		Name: ast.NewIdent("TestCreateUpdateDelete" + tbl.GoTypeName),
-		Type: &ast.FuncType{
-			Params: &ast.FieldList{
-				List: []*ast.Field{{
-					Names: []*ast.Ident{ast.NewIdent("t")},
-					Type:  ast.NewIdent("*testing.T"),
-				}},
-			},
-		},
+		Type: testFuncType,
 		Body: &ast.BlockStmt{
-			List: []ast.Stmt{
-				// item := Item{Description: "an item"}
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{testObj},
-					Tok: token.DEFINE,
-					Rhs: []ast.Expr{&ast.CompositeLit{
-						Type: ast.NewIdent(tbl.GoTypeName),
-						Elts: []ast.Expr{
-							&ast.KeyValueExpr{
-								Key:   fieldName,
-								Value: &ast.BasicLit{Kind: token.STRING, Value: description1},
+			List: func() []ast.Stmt {
+				assertNotZero := func(obj *ast.Ident, field string) *ast.ExprStmt {
+					return &ast.ExprStmt{X: &ast.CallExpr{
+						Fun:  &ast.SelectorExpr{X: ast.NewIdent("assert"), Sel: ast.NewIdent("NotZero")},
+						Args: []ast.Expr{ast.NewIdent("t"), &ast.SelectorExpr{X: obj, Sel: ast.NewIdent(field)}},
+					}}
+				}
+
+				stmts := []ast.Stmt{
+					// item := Item{Description: "an item"}
+					&ast.AssignStmt{
+						Lhs: []ast.Expr{testObj},
+						Tok: token.DEFINE,
+						Rhs: []ast.Expr{&ast.CompositeLit{
+							Type: ast.NewIdent(tbl.GoTypeName),
+							Elts: []ast.Expr{
+								&ast.KeyValueExpr{
+									Key:   fieldName,
+									Value: &ast.BasicLit{Kind: token.STRING, Value: description1},
+								},
 							},
+						}},
+					},
+
+					// TestDB.SaveItem(&item)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun:  &ast.SelectorExpr{X: ast.NewIdent("TestDB"), Sel: ast.NewIdent("Save" + tbl.GoTypeName)},
+						Args: []ast.Expr{&ast.UnaryExpr{Op: token.AND, X: testObj}},
+					}},
+
+					// require.NotZero(t, item.ID)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun:  &ast.SelectorExpr{X: ast.NewIdent("require"), Sel: ast.NewIdent("NotZero")},
+						Args: []ast.Expr{ast.NewIdent("t"), &ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
+					}},
+				}
+
+				// After create: assert timestamps are set
+				if hasCreatedAt {
+					stmts = append(stmts, assertNotZero(testObj, "CreatedAt"))
+				}
+				if hasUpdatedAt {
+					stmts = append(stmts, assertNotZero(testObj, "UpdatedAt"))
+				}
+
+				stmts = append(stmts,
+					// item2 := Must(TestDB.GetItemByID(item.ID))
+					&ast.AssignStmt{
+						Lhs: []ast.Expr{testObj2},
+						Tok: token.DEFINE,
+						Rhs: []ast.Expr{mustCall(&ast.CallExpr{
+							Fun:  &ast.SelectorExpr{X: ast.NewIdent("TestDB"), Sel: ast.NewIdent("Get" + tbl.GoTypeName + "ByID")},
+							Args: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
+						})},
+					},
+
+					// assert.Equal(t, "an item", item2.Description)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun: &ast.SelectorExpr{X: ast.NewIdent("assert"), Sel: ast.NewIdent("Equal")},
+						Args: []ast.Expr{
+							ast.NewIdent("t"),
+							&ast.BasicLit{Kind: token.STRING, Value: description1},
+							&ast.SelectorExpr{X: testObj2, Sel: fieldName},
 						},
 					}},
-				},
 
-				// TestDB.SaveItem(&item)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun:  ast.NewIdent("TestDB.Save" + tbl.GoTypeName),
-					Args: []ast.Expr{&ast.UnaryExpr{Op: token.AND, X: testObj}},
-				}},
+					// item.Description = "a big item"
+					&ast.AssignStmt{
+						Lhs: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: fieldName}},
+						Tok: token.ASSIGN,
+						Rhs: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: description2}},
+					},
 
-				// require.NotZero(t, item.ID)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun:  ast.NewIdent("require.NotZero"),
-					Args: []ast.Expr{ast.NewIdent("t"), &ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
-				}},
+					// TestDB.SaveItem(&item)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun:  &ast.SelectorExpr{X: ast.NewIdent("TestDB"), Sel: ast.NewIdent("Save" + tbl.GoTypeName)},
+						Args: []ast.Expr{&ast.UnaryExpr{Op: token.AND, X: testObj}},
+					}},
+				)
 
-				// item2 := Must(TestDB.GetItemByID(item.ID))
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{testObj2},
-					Tok: token.DEFINE,
-					Rhs: []ast.Expr{&ast.CallExpr{
-						Fun: ast.NewIdent("Must"),
-						Args: []ast.Expr{&ast.CallExpr{
-							Fun:  ast.NewIdent("TestDB.Get" + tbl.GoTypeName + "ByID"),
+				stmts = append(stmts,
+					// item2 = Must(TestDB.GetItemByID(item.ID))
+					&ast.AssignStmt{
+						Lhs: []ast.Expr{testObj2},
+						Tok: token.ASSIGN,
+						Rhs: []ast.Expr{mustCall(&ast.CallExpr{
+							Fun:  &ast.SelectorExpr{X: ast.NewIdent("TestDB"), Sel: ast.NewIdent("Get" + tbl.GoTypeName + "ByID")},
+							Args: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
+						})},
+					},
+
+					// assert.Equal(t, item.Description, item2.Description)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun: &ast.SelectorExpr{X: ast.NewIdent("assert"), Sel: ast.NewIdent("Equal")},
+						Args: []ast.Expr{
+							ast.NewIdent("t"),
+							&ast.SelectorExpr{X: testObj, Sel: fieldName},
+							&ast.SelectorExpr{X: testObj2, Sel: fieldName},
+						},
+					}},
+
+					// TestDB.DeleteItem(item)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun:  &ast.SelectorExpr{X: ast.NewIdent("TestDB"), Sel: ast.NewIdent("Delete" + tbl.GoTypeName)},
+						Args: []ast.Expr{testObj},
+					}},
+
+					// _, err := TestDB.GetItemByID(item.ID)
+					&ast.AssignStmt{
+						Lhs: []ast.Expr{ast.NewIdent("_"), ast.NewIdent("err")},
+						Tok: token.DEFINE,
+						Rhs: []ast.Expr{&ast.CallExpr{
+							Fun:  &ast.SelectorExpr{X: ast.NewIdent("TestDB"), Sel: ast.NewIdent("Get" + tbl.GoTypeName + "ByID")},
 							Args: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
 						}},
-					}},
-				},
-
-				// assert.Equal(t, "an item", item2.Description)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun: ast.NewIdent("assert.Equal"),
-					Args: []ast.Expr{
-						ast.NewIdent("t"),
-						&ast.BasicLit{Kind: token.STRING, Value: description1},
-						&ast.SelectorExpr{X: testObj2, Sel: fieldName},
 					},
-				}},
 
-				// item.Description = "a big item"
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: fieldName}},
-					Tok: token.ASSIGN,
-					Rhs: []ast.Expr{&ast.BasicLit{Kind: token.STRING, Value: description2}},
-				},
-
-				// TestDB.SaveItem(&item)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun:  ast.NewIdent("TestDB.Save" + tbl.GoTypeName),
-					Args: []ast.Expr{&ast.UnaryExpr{Op: token.AND, X: testObj}},
-				}},
-
-				// item2 = Must(TestDB.GetItemByID(item.ID))
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{testObj2},
-					Tok: token.ASSIGN,
-					Rhs: []ast.Expr{&ast.CallExpr{
-						Fun: ast.NewIdent("Must"),
-						Args: []ast.Expr{&ast.CallExpr{
-							Fun:  ast.NewIdent("TestDB.Get" + tbl.GoTypeName + "ByID"),
-							Args: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
-						}},
+					// assert.ErrorIs(t, err, db.ErrNotInDB)
+					&ast.ExprStmt{X: &ast.CallExpr{
+						Fun: &ast.SelectorExpr{X: ast.NewIdent("assert"), Sel: ast.NewIdent("ErrorIs")},
+						Args: []ast.Expr{
+							ast.NewIdent("t"),
+							ast.NewIdent("err"),
+							ast.NewIdent("ErrNotInDB"),
+						},
 					}},
-				},
+				)
 
-				// assert.Equal(t, item.Description, item2.Description)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun: ast.NewIdent("assert.Equal"),
-					Args: []ast.Expr{
-						ast.NewIdent("t"),
-						&ast.SelectorExpr{X: testObj, Sel: fieldName},
-						&ast.SelectorExpr{X: testObj2, Sel: fieldName},
-					},
-				}},
-
-				// TestDB.DeleteItem(item)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun:  ast.NewIdent("TestDB.Delete" + tbl.GoTypeName),
-					Args: []ast.Expr{testObj},
-				}},
-
-				// _, err := TestDB.GetItemByID(item.ID)
-				&ast.AssignStmt{
-					Lhs: []ast.Expr{ast.NewIdent("_"), ast.NewIdent("err")},
-					Tok: token.DEFINE,
-					Rhs: []ast.Expr{&ast.CallExpr{
-						Fun:  ast.NewIdent("TestDB.Get" + tbl.GoTypeName + "ByID"),
-						Args: []ast.Expr{&ast.SelectorExpr{X: testObj, Sel: ast.NewIdent("ID")}},
-					}},
-				},
-
-				// assert.ErrorIs(t, err, db.ErrNotInDB)
-				&ast.ExprStmt{X: &ast.CallExpr{
-					Fun: ast.NewIdent("assert.ErrorIs"),
-					Args: []ast.Expr{
-						ast.NewIdent("t"),
-						ast.NewIdent("err"),
-						&ast.SelectorExpr{X: ast.NewIdent("db"), Sel: ast.NewIdent("ErrNotInDB")},
-					},
-				}},
-			},
+				return stmts
+			}(),
 		},
 	}
 
 	testGetAll := &ast.FuncDecl{
 		Name: ast.NewIdent("TestGetAll" + inflection.Plural(tbl.GoTypeName)),
-		Type: &ast.FuncType{Params: &ast.FieldList{List: []*ast.Field{
-			{Names: []*ast.Ident{ast.NewIdent("t")}, Type: &ast.StarExpr{X: ast.NewIdent("testing.T")}},
-		}}, Results: nil},
+		Type: testFuncType,
 		Body: &ast.BlockStmt{
 			List: []ast.Stmt{
 				&ast.AssignStmt{
@@ -237,17 +212,110 @@ func GenerateModelTestAST(tbl schema.Table, gomodName string) *ast.File {
 		},
 	}
 
+	shouldIncludeTestFkCheck := false
+	testFkChecking := &ast.FuncDecl{
+		Name: ast.NewIdent("Test" + tbl.GoTypeName + "FkChecking"),
+		Type: testFuncType,
+		Body: &ast.BlockStmt{
+			List: func() []ast.Stmt {
+				// post := MakePost()
+				stmts := []ast.Stmt{
+					&ast.AssignStmt{
+						Lhs: []ast.Expr{ast.NewIdent(tbl.VarName)},
+						Tok: token.DEFINE,
+						Rhs: []ast.Expr{
+							&ast.CallExpr{
+								Fun: ast.NewIdent("Make" + tbl.GoTypeName),
+							},
+						},
+					},
+				}
+				for _, col := range tbl.Columns {
+					if col.IsForeignKey {
+						shouldIncludeTestFkCheck = true
+						stmts = append(stmts, []ast.Stmt{
+
+							// post.QuotedPostID = 94354538969386985
+							&ast.AssignStmt{
+								Lhs: []ast.Expr{
+									&ast.SelectorExpr{
+										X:   ast.NewIdent(tbl.VarName),
+										Sel: ast.NewIdent(col.GoFieldName()),
+									},
+								},
+								Tok: token.ASSIGN,
+								Rhs: []ast.Expr{
+									&ast.BasicLit{
+										Kind:  token.INT,
+										Value: "94354538969386985",
+									},
+								},
+							},
+
+							// err := db.SavePost(&post)
+							&ast.AssignStmt{
+								Lhs: []ast.Expr{ast.NewIdent("err")},
+								Tok: token.DEFINE,
+								Rhs: []ast.Expr{
+									&ast.CallExpr{
+										Fun: &ast.SelectorExpr{
+											X:   ast.NewIdent("TestDB"),
+											Sel: ast.NewIdent("Save" + tbl.GoTypeName),
+										},
+										Args: []ast.Expr{
+											&ast.UnaryExpr{
+												Op: token.AND,
+												X:  ast.NewIdent(tbl.VarName),
+											},
+										},
+									},
+								},
+							},
+
+							// assertForeignKeyError(t, err, "QuotedPostID", post.QuotedPostID)
+							&ast.ExprStmt{
+								X: &ast.CallExpr{
+									Fun: ast.NewIdent("AssertForeignKeyError"),
+									Args: []ast.Expr{
+										ast.NewIdent("t"),
+										ast.NewIdent("err"),
+										&ast.BasicLit{
+											Kind:  token.STRING,
+											Value: fmt.Sprintf("%q", col.GoFieldName()),
+										},
+										&ast.SelectorExpr{
+											X:   ast.NewIdent(tbl.VarName),
+											Sel: ast.NewIdent(col.GoFieldName()),
+										},
+									},
+								},
+							},
+						}...)
+					}
+				}
+				return stmts
+			}(),
+		},
+	}
+
+	testList := []ast.Decl{
+		makeItemFunc,
+		testCreateUpdateDelete,
+		testGetAll,
+	}
+	if shouldIncludeTestFkCheck {
+		testList = append(testList, testFkChecking)
+	}
 	return &ast.File{
 		Name: ast.NewIdent(testpackageName),
-		Decls: []ast.Decl{
+		Decls: append([]ast.Decl{
 			&ast.GenDecl{
 				Tok: token.IMPORT,
 				Specs: []ast.Spec{
-					&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"fmt"`}},
 					&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"testing"`}},
 					&ast.ImportSpec{
 						Path: &ast.BasicLit{Kind: token.STRING, Value: `"git.offline-twitter.com/offline-labs/gas-stack/pkg/db"`},
-						Name: ast.NewIdent("db"),
+						Name: ast.NewIdent("."),
 					},
 					&ast.ImportSpec{
 						Path: &ast.BasicLit{Kind: token.STRING, Value: `"git.offline-twitter.com/offline-labs/gas-stack/pkg/flowutils"`},
@@ -261,17 +329,6 @@ func GenerateModelTestAST(tbl schema.Table, gomodName string) *ast.File {
 					&ast.ImportSpec{Path: &ast.BasicLit{Kind: token.STRING, Value: `"github.com/stretchr/testify/require"`}},
 				},
 			},
-			// var TestDB *DB
-			testDBDecl,
-
-			// func init() { TestDB = MakeDB("tmp") }
-			initFuncDecl,
-
-			// func MakeDB(dbName string) *DB { db := Must(Create(fmt.Sprintf("file:%s?mode=memory&cache=shared", dbName))); return db }
-			makeDBHelperDecl,
-
-			testCreateUpdateDelete,
-			testGetAll,
-		},
+		}, testList...),
 	}
 }

pkg/codegen/pkg.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	"os/exec"
+	"text/template"
 
 	. "git.offline-twitter.com/offline-labs/gas-stack/pkg/flowutils"
 )
@@ -39,6 +40,11 @@ func InitPkg(opts PkgOpts) {
 	PanicIf(os.WriteFile("pkg/db/schema.sql", Must(tpl.ReadFile("tpl/schema.sql")), 0o664))
 	PanicIf(os.WriteFile("pkg/db/db.go", Must(tpl.ReadFile("tpl/db.go.tpl")), 0o664))
 
+	dbTest := Must(os.Create("pkg/db/db_test.go"))
+	defer MustClose(dbTest)
+	t := Must(template.ParseFS(tpl, "tpl/db_test.go.tpl"))
+	PanicIf(t.Execute(dbTest, opts))
+
 	PanicIf(os.WriteFile("sample_data/mount.sh", Must(tpl.ReadFile("tpl/mount.sh")), 0o775))
 	PanicIf(os.WriteFile("sample_data/reset.sh", Must(tpl.ReadFile("tpl/reset.sh")), 0o775))
 

pkg/codegen/tpl/db_test.go.tpl

@@ -0,0 +1,19 @@
+package db_test
+
+import (
+	"fmt"
+
+	. "git.offline-twitter.com/offline-labs/gas-stack/pkg/flowutils"
+
+	. "{{ .ModuleName }}/pkg/db"
+)
+
+var TestDB *DB
+
+func init() {
+	TestDB = MakeDB("tmp")
+}
+func MakeDB(dbName string) *DB {
+	db := Must(Create(fmt.Sprintf("file:%s?mode=memory&cache=shared", dbName)))
+	return db
+}

pkg/db/errors_test_helper.go

@@ -0,0 +1,21 @@
+package db
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func AssertForeignKeyError[T ForeignKey](t *testing.T, err error, field string, val T) {
+	t.Helper()
+
+	var fkErr ForeignKeyError[T]
+	require.Error(t, err)
+	require.ErrorIs(t, err, ErrForeignKeyViolation)
+	// ErrorAs produces terrible error messages if it's a ForeignKeyError with a different type
+	// parameter (i.e., if it was a different field that failed).
+	require.ErrorAs(t, err, &fkErr, "expected error field: %q", field)
+	assert.Equal(t, field, fkErr.Field)
+	assert.Equal(t, val, fkErr.FkValue)
+}

pkg/flowutils/flowutils.go

@@ -1,5 +1,7 @@
 package flowutils
 
+import "io"
+
 func PanicIf(err error) {
 	if err != nil {
 		panic(err)
@@ -10,3 +12,7 @@ func Must[T any](val T, err error) T {
 	PanicIf(err)
 	return val
 }
+
+func MustClose(closer io.Closer) {
+	PanicIf(closer.Close())
+}

pkg/schema/migration_verification_test.go

@@ -0,0 +1,167 @@
+package schema_test
+
+import (
+	"slices"
+	"testing"
+
+	"github.com/go-test/deep"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"git.offline-twitter.com/offline-labs/gas-stack/pkg/db"
+	"git.offline-twitter.com/offline-labs/gas-stack/pkg/flowutils"
+	"git.offline-twitter.com/offline-labs/gas-stack/pkg/schema"
+)
+
+var (
+	baseSchema = `
+		create table db_version (
+		    version integer primary key
+		) strict, without rowid;
+		insert into db_version values(0);
+
+		create table t1 (
+			rowid integer primary key,
+			data1 integer not null,
+			data2 text not null
+		);
+	`
+
+	fullSchema = `
+		create table db_version (
+		    version integer primary key
+		) strict, without rowid;
+		insert into db_version values(2);
+
+		create table t1 (
+			rowid integer primary key,
+			data1 integer not null,
+			data2 text not null,
+			data3 integer
+		);
+		create table t2 (
+			rowid integer primary key
+		);
+	`
+)
+
+func TestVerifyCorrectMigration(t *testing.T) {
+	db1 := schema.InitDB(fullSchema)
+	db1Schema := schema.SchemaFromDB(db1)
+
+	t.Run("migrate in 1 step", func(t *testing.T) {
+		migration := `
+			create table t2 (
+				rowid integer primary key
+			);
+			alter table t1 add column data3 integer;
+		`
+		db2Config := db.Init(&baseSchema, &[]string{migration})
+		db2 := flowutils.Must(db2Config.Create(":memory:"))
+		require.NoError(t, db2Config.CheckAndUpdateVersion(db2))
+		db2Schema := schema.SchemaFromDB(db2)
+
+		if diff := deep.Equal(db1Schema, db2Schema); diff != nil {
+			t.Error(diff)
+		}
+	})
+
+	t.Run("migrate in 2 steps", func(t *testing.T) {
+		migration1 := `
+			create table t2 (
+				rowid integer primary key
+			);
+		`
+		migration2 := `
+			alter table t1 add column data3 integer;
+		`
+
+		db2Config := db.Init(&baseSchema, &[]string{migration1, migration2})
+		db2 := flowutils.Must(db2Config.Create(":memory:"))
+		require.NoError(t, db2Config.CheckAndUpdateVersion(db2))
+		db2Schema := schema.SchemaFromDB(db2)
+
+		if diff := deep.Equal(db1Schema, db2Schema); diff != nil {
+			t.Error(diff)
+		}
+	})
+}
+
+func TestIncorrectMigrations(t *testing.T) {
+	db1 := schema.InitDB(fullSchema)
+	db1Schema := schema.SchemaFromDB(db1)
+
+	t.Run("missing migration", func(t *testing.T) {
+		db2Config := db.Init(&baseSchema, &[]string{})
+		db2 := flowutils.Must(db2Config.Create(":memory:"))
+		require.NoError(t, db2Config.CheckAndUpdateVersion(db2))
+		db2Schema := schema.SchemaFromDB(db2)
+
+		// Missing a table
+		assert.Len(t, db1Schema.Tables, len(db2Schema.Tables)+1)
+		assert.Contains(t, db1Schema.Tables, "t2")
+		assert.NotContains(t, db2Schema.Tables, "t2")
+
+		// Missing the new column
+		assert.Len(t, db1Schema.Tables["t1"].Columns, len(db2Schema.Tables["t1"].Columns)+1)
+		assert.True(t, slices.ContainsFunc(db1Schema.Tables["t1"].Columns, func(c schema.Column) bool { return c.Name == "data3" }), "t2")
+		assert.False(t, slices.ContainsFunc(db2Schema.Tables["t1"].Columns, func(c schema.Column) bool { return c.Name == "data3" }), "t2")
+	})
+
+	t.Run("incomplete migration", func(t *testing.T) {
+		db2Config := db.Init(&baseSchema, &[]string{`
+				create table t2 (
+					rowid integer primary key
+				);
+			`})
+		db2 := flowutils.Must(db2Config.Create(":memory:"))
+		require.NoError(t, db2Config.CheckAndUpdateVersion(db2))
+		db2Schema := schema.SchemaFromDB(db2)
+
+		// Has the new table
+		assert.Len(t, db1Schema.Tables, len(db2Schema.Tables))
+		assert.Contains(t, db1Schema.Tables, "t2")
+		assert.Contains(t, db2Schema.Tables, "t2")
+
+		// Still missing the new column
+		assert.Len(t, db1Schema.Tables["t1"].Columns, len(db2Schema.Tables["t1"].Columns)+1)
+		assert.True(t, slices.ContainsFunc(db1Schema.Tables["t1"].Columns, func(c schema.Column) bool { return c.Name == "data3" }), "t2")
+		assert.False(t, slices.ContainsFunc(db2Schema.Tables["t1"].Columns, func(c schema.Column) bool { return c.Name == "data3" }), "t2")
+	})
+
+	t.Run("incorrect migration (wrong data type)", func(t *testing.T) {
+		db2Config := db.Init(&baseSchema, &[]string{`
+			create table t2 (
+				rowid integer primary key
+			);
+			alter table t1 add column data3 text;
+		`})
+		db2 := flowutils.Must(db2Config.Create(":memory:"))
+		require.NoError(t, db2Config.CheckAndUpdateVersion(db2))
+		db2Schema := schema.SchemaFromDB(db2)
+
+		// Has the new table
+		assert.Len(t, db1Schema.Tables, len(db2Schema.Tables))
+		assert.Contains(t, db1Schema.Tables, "t2")
+		assert.Contains(t, db2Schema.Tables, "t2")
+
+		// Has the right column, but it's the wrong type
+		assert.Len(t, db1Schema.Tables["t1"].Columns, len(db2Schema.Tables["t1"].Columns))
+		col1 := db1Schema.Tables["t1"].Columns[slices.IndexFunc(
+			db1Schema.Tables["t1"].Columns,
+			func(c schema.Column) bool { return c.Name == "data3" },
+		)]
+		col2 := db2Schema.Tables["t1"].Columns[slices.IndexFunc(
+			db2Schema.Tables["t1"].Columns,
+			func(c schema.Column) bool { return c.Name == "data3" },
+		)]
+
+		assert.NotEqual(t, col1, col2)
+		assert.Equal(t, col1.Type, "integer") // Full schema has an integer column
+		assert.Equal(t, col2.Type, "text")    // Migration incorrectly uses a text column
+
+		// Other than that they are equal
+		col2.Type = "integer"
+		assert.Equal(t, col1, col2)
+	})
+}

pkg/schema/parse.go

@@ -21,7 +21,6 @@ var create_views string
 func InitDB(sql_schema string) *sqlx.DB {
 	db := sqlx.MustOpen("sqlite3", ":memory:")
 	db.MustExec(sql_schema)
-	db.MustExec(create_views)
 	return db
 }
 
@@ -36,6 +35,7 @@ func SchemaFromSQLFile(filepath string) (Schema, error) {
 // SchemaFromDB takes a DB connection, checks its schema metadata tables, and returns a Schema.
 func SchemaFromDB(db *sqlx.DB) Schema {
 	ret := Schema{Tables: map[string]Table{}, Indexes: map[string]Index{}}
+	db.MustExec(create_views)
 
 	var tables []Table
 	PanicIf(db.Select(&tables, `select name, table_type, is_strict, is_without_rowid from tables`))

pkg/schema/table.go

@@ -1,5 +1,12 @@
 package schema
 
+import (
+	"sort"
+	"strings"
+
+	"git.offline-twitter.com/offline-labs/gas-stack/pkg/textutils"
+)
+
 // Column represents a single column in a table.
 type Column struct {
 	TableName              string `db:"table_name"`
@@ -20,6 +27,43 @@ func (c Column) IsNullableForeignKey() bool {
 	return !c.IsNotNull && !c.IsPrimaryKey && c.IsForeignKey
 }
 
+func (c Column) IsNonCodeTableForeignKey() bool {
+	return c.IsForeignKey && strings.HasSuffix(c.Name, "_id")
+}
+
+func (c Column) GoFieldName() string {
+	if c.Name == "rowid" {
+		return "ID"
+	}
+	if c.IsNonCodeTableForeignKey() {
+		return textutils.SnakeToCamel(strings.TrimSuffix(c.Name, "_id")) + "ID"
+	}
+	return textutils.SnakeToCamel(c.Name)
+}
+
+func (c Column) GoType() string {
+	if c.IsNonCodeTableForeignKey() {
+		return TypenameFromTablename(c.ForeignKeyTargetTable) + "ID"
+	}
+	switch c.Type {
+	case "integer", "int":
+		if strings.HasPrefix(c.Name, "is_") || strings.HasPrefix(c.Name, "has_") {
+			return "bool"
+		} else if strings.HasSuffix(c.Name, "_at") {
+			return "Timestamp"
+		}
+		return "int"
+	case "text":
+		return "string"
+	case "real":
+		return "float32"
+	case "blob":
+		return "[]byte"
+	default:
+		panic("Unrecognized sqlite column type: " + c.Type)
+	}
+}
+
 // Table is a single SQLite table.
 type Table struct {
 	TableName string `db:"name"`
@@ -40,6 +84,35 @@ type Table struct {
 	GoTypeName string
 }
 
+// PrimaryKeyColumns returns the ordered list of columns in this table's primary key.
+// This can be useful for "without rowid" tables with composite primary keys.
+//
+// TODO: needs test
+func (t Table) PrimaryKeyColumns() []Column {
+	pks := make([]Column, 0)
+	for _, c := range t.Columns {
+		if c.IsPrimaryKey {
+			pks = append(pks, c)
+		}
+	}
+	sort.Slice(pks, func(i, j int) bool {
+		return pks[i].PrimaryKeyRank < pks[j].PrimaryKeyRank
+	})
+	return pks
+}
+
+func (t Table) HasAutoTimestamps() (hasCreatedAt bool, hasUpdatedAt bool) {
+	for _, c := range t.Columns {
+		if c.Name == "created_at" && c.Type == "integer" {
+			hasCreatedAt = true
+		}
+		if c.Name == "updated_at" && c.Type == "integer" {
+			hasUpdatedAt = true
+		}
+	}
+	return
+}
+
 type Index struct {
 	Name      string `db:"index_name"`
 	TableName string `db:"table_name"`