codegen: wrap foreign key checks for nullable FKs in "if a.Val != 0 { ... }"

pkg/codegen/modelgenerate/generate_model.go

@@ -161,9 +161,21 @@ func buildFKCheckLambda(tbl schema.Table) (*ast.AssignStmt, bool) {
 							structFieldName := col.GoFieldName()
 							structField := &ast.SelectorExpr{X: ast.NewIdent(tbl.VarName), Sel: ast.NewIdent(structFieldName)}
 
+							ret = append(ret, func() ast.Stmt {
+								// Wrap nullable FKs in "if a.val != 0 { ... }"
+								wrap := func(input ast.Stmt) ast.Stmt {
+									if col.IsNullableForeignKey() {
+										return &ast.IfStmt{
+											Cond: &ast.BinaryExpr{X: structField, Op: token.NEQ, Y: &ast.BasicLit{Kind: token.INT, Value: "0"}},
+											Body: &ast.BlockStmt{List: []ast.Stmt{input}},
+										}
+									} else {
+										return input
+									}
+								}
 								if col.IsNonCodeTableForeignKey() {
 									// Real foreign key; look up referent by ID to see if it exists
-								ret = append(ret, &ast.IfStmt{
+									return wrap(&ast.IfStmt{
 										Init: &ast.AssignStmt{
 											Lhs: []ast.Expr{ast.NewIdent("_"), ast.NewIdent("err")},
 											Tok: token.DEFINE,
@@ -197,7 +209,7 @@ func buildFKCheckLambda(tbl schema.Table) (*ast.AssignStmt, bool) {
 									})
 								} else {
 									// Code table value.  Query the table to see if it exists
-								ret = append(ret, &ast.IfStmt{
+									return wrap(&ast.IfStmt{
 										Init: &ast.AssignStmt{
 											Lhs: []ast.Expr{ast.NewIdent("err")},
 											Tok: token.DEFINE,
@@ -234,6 +246,7 @@ func buildFKCheckLambda(tbl schema.Table) (*ast.AssignStmt, bool) {
 										},
 									})
 								}
+							}())
 						}
 						// final return nil
 						ret = append(ret, &ast.ReturnStmt{Results: []ast.Expr{ast.NewIdent("nil")}})