boolnames: make default whitelist include 'ok'

pkg/ifinit/analyzer.go

@@ -0,0 +1,195 @@
+// Package ifinit reports if-statement init clauses that span more than one line.
+package ifinit
+
+import (
+	"fmt"
+	"go/ast"
+	"go/token"
+	"strings"
+
+	"golang.org/x/tools/go/analysis"
+	"golang.org/x/tools/go/analysis/passes/inspect"
+	"golang.org/x/tools/go/ast/inspector"
+)
+
+const doc = `checks that if-statement init clauses occupy a single line
+
+A multi-line init clause pushes the condition being tested far away from the
+"if" keyword, so the reader has to scan past the setup to find out what is
+actually being decided. The fix hoists the init clause into its own statement
+above the if.`
+
+var Analyzer = &analysis.Analyzer{
+	Name:     "ifinit",
+	Doc:      doc,
+	Requires: []*analysis.Analyzer{inspect.Analyzer},
+	Run:      run,
+}
+
+func run(pass *analysis.Pass) (any, error) {
+	insp, ok := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
+	if !ok {
+		panic("inspect.Analyzer did not produce *inspector.Inspector")
+	}
+
+	insp.WithStack([]ast.Node{(*ast.IfStmt)(nil)}, func(n ast.Node, isPush bool, stack []ast.Node) bool {
+		if !isPush {
+			return false
+		}
+
+		stmt, ok := n.(*ast.IfStmt)
+		if !ok {
+			panic("inspector passed a non-IfStmt node to an IfStmt stack walk")
+		}
+		if stmt.Init == nil {
+			return true
+		}
+
+		start := pass.Fset.Position(stmt.Init.Pos())
+		end := pass.Fset.Position(stmt.Init.End())
+		if start.Line == end.Line {
+			return true
+		}
+
+		diag := analysis.Diagnostic{
+			Pos:     stmt.Init.Pos(),
+			End:     stmt.Init.End(),
+			Message: fmt.Sprintf("if statement init clause spans %d lines; it must be on a single line", end.Line-start.Line+1),
+		}
+
+		if fix, ok := hoist(pass, stmt, stack); ok {
+			diag.SuggestedFixes = []analysis.SuggestedFix{fix}
+		}
+
+		pass.Report(diag)
+
+		return true
+	})
+
+	return nil, nil
+}
+
+// hoist rewrites "if <init>; <cond> {" into "<init>" on its own line followed by
+// "if <cond> {". The init clause's own text is left untouched, so comments and
+// internal line breaks survive.
+func hoist(pass *analysis.Pass, stmt *ast.IfStmt, stack []ast.Node) (analysis.SuggestedFix, bool) {
+	if !isHoistable(stmt, stack) {
+		return analysis.SuggestedFix{}, false
+	}
+
+	if !isShadowSafe(pass, stmt) {
+		return analysis.SuggestedFix{}, false
+	}
+
+	indent, ok := lineIndent(pass, stmt.Pos())
+	if !ok {
+		return analysis.SuggestedFix{}, false
+	}
+
+	return analysis.SuggestedFix{
+		Message: "Hoist the init clause above the if statement",
+		TextEdits: []analysis.TextEdit{
+			// Drop the leading "if ".
+			{Pos: stmt.Pos(), End: stmt.Init.Pos()},
+			// Turn the "; " separator into a line break and a fresh "if ".
+			{Pos: stmt.Init.End(), End: stmt.Cond.Pos(), NewText: []byte("\n" + indent + "if ")},
+		},
+	}, true
+}
+
+func isHoistable(stmt *ast.IfStmt, stack []ast.Node) bool {
+	if len(stack) < 2 {
+		return false
+	}
+
+	switch parent := stack[len(stack)-2].(type) {
+	case *ast.IfStmt:
+		// An "else if": the init clause cannot move above the chain without
+		// restructuring the whole thing into a nested else block.
+		return parent.Else != ast.Stmt(stmt)
+	case *ast.LabeledStmt:
+		// Hoisting would leave the label pointing at the init clause instead.
+		return false
+	}
+
+	return true
+}
+
+// shadowSafe reports whether hoisting stmt's init clause out of the if's scope
+// leaves every name it binds meaning the same thing.
+//
+// Only ":=" declares anything, and only in the if statement's own scope. Moving
+// that declaration up one level is safe exactly when none of the names it binds
+// already resolve to something in the enclosing scope: otherwise the hoisted
+// ":=" either assigns to that existing object instead of declaring a fresh one,
+// or collides with a later declaration in the same block.
+//
+// The check is deliberately conservative. It refuses whenever a name resolves at
+// all -- including to a package-level or universe name -- rather than trying to
+// prove that nothing reads the shadowed object afterwards.
+func isShadowSafe(pass *analysis.Pass, stmt *ast.IfStmt) bool {
+	assign, ok := stmt.Init.(*ast.AssignStmt)
+	if !ok || assign.Tok != token.DEFINE {
+		return true
+	}
+
+	scope := pass.TypesInfo.Scopes[stmt]
+	if scope == nil {
+		return false
+	}
+
+	enclosing := scope.Parent()
+	if enclosing == nil {
+		return false
+	}
+
+	for _, lhs := range assign.Lhs {
+		ident, ok := lhs.(*ast.Ident)
+		if !ok {
+			return false
+		}
+
+		if ident.Name == "_" {
+			continue
+		}
+
+		// token.NoPos makes the lookup ignore declaration order, so a name
+		// declared later in the same block counts as a conflict too.
+		if _, obj := enclosing.LookupParent(ident.Name, token.NoPos); obj != nil {
+			return false
+		}
+	}
+
+	return true
+}
+
+// lineIndent returns the whitespace preceding pos on its line, and reports
+// whether pos is the first non-whitespace token on that line.
+func lineIndent(pass *analysis.Pass, pos token.Pos) (string, bool) {
+	if pass.ReadFile == nil {
+		return "", false
+	}
+
+	file := pass.Fset.File(pos)
+	if file == nil {
+		return "", false
+	}
+
+	src, err := pass.ReadFile(file.Name())
+	if err != nil {
+		return "", false
+	}
+
+	lineStart := file.Offset(file.LineStart(file.Line(pos)))
+	offset := file.Offset(pos)
+	if offset > len(src) {
+		return "", false
+	}
+
+	prefix := string(src[lineStart:offset])
+	if strings.TrimLeft(prefix, " \t") != "" {
+		return "", false
+	}
+
+	return prefix, true
+}

pkg/ifinit/analyzer_test.go

@@ -0,0 +1,13 @@
+package ifinit_test
+
+import (
+	"testing"
+
+	"golang.org/x/tools/go/analysis/analysistest"
+
+	"git.offline-twitter.com/offline-labs/go-lint/pkg/ifinit"
+)
+
+func TestAnalyzer(t *testing.T) {
+	analysistest.RunWithSuggestedFixes(t, analysistest.TestData(), ifinit.Analyzer, "cases")
+}

pkg/ifinit/plugin.go

@@ -0,0 +1,24 @@
+package ifinit
+
+import (
+	"github.com/golangci/plugin-module-register/register"
+	"golang.org/x/tools/go/analysis"
+)
+
+func init() {
+	register.Plugin("ifinit", New)
+}
+
+type plugin struct{}
+
+func New(any) (register.LinterPlugin, error) {
+	return &plugin{}, nil
+}
+
+func (p *plugin) BuildAnalyzers() ([]*analysis.Analyzer, error) {
+	return []*analysis.Analyzer{Analyzer}, nil
+}
+
+func (p *plugin) GetLoadMode() string {
+	return register.LoadModeTypesInfo
+}

pkg/ifinit/testdata/src/cases/scopes.go

@@ -0,0 +1,88 @@
+package cases
+
+func do(args ...int) error { return nil }
+
+var errState error
+
+// Safe: both names are fresh in the block that would receive the hoisted statement.
+func freshNames() {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}
+
+// Safe: "_" declares nothing and err is fresh.
+func blankAndFresh() {
+	if _, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = err
+	}
+}
+
+// Safe: "=" assigns to an existing variable; it declares nothing at all.
+func plainAssign() error {
+	var err error
+
+	if err = do( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Unsafe: err already exists in the enclosing block. Hoisting the ":=" would
+// assign to that err rather than declaring a new one, so the returned error
+// would silently change.
+func shadowsExistingLocal() error {
+	v, err := multi(1)
+	if err != nil {
+		return err
+	}
+	_ = v
+
+	if v2, err := multi( // want `init clause spans 3 lines`
+		2,
+	); err != nil {
+		_ = v2
+	}
+
+	return err
+}
+
+// Unsafe: the same names are redeclared later in this block, so hoisting turns
+// the later ":=" into "no new variables on left side of :=".
+func declaredLaterInBlock() {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+
+	v, err := multi(2)
+	_, _ = v, err
+}
+
+// Unsafe: err is a parameter, so hoisting would rebind it for the rest of the body.
+func shadowsParam(err error) {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}
+
+// Conservatively refused: shadowing a package-level name. Nothing reads errState
+// after the if here, so this one would in fact be safe -- the check does not try
+// to prove that.
+func shadowsPackageLevel() {
+	if v, errState := multi( // want `init clause spans 3 lines`
+		1,
+	); errState != nil {
+		_ = v
+	}
+}

pkg/ifinit/testdata/src/cases/scopes.go.golden

@@ -0,0 +1,91 @@
+package cases
+
+func do(args ...int) error { return nil }
+
+var errState error
+
+// Safe: both names are fresh in the block that would receive the hoisted statement.
+func freshNames() {
+	v, err := multi( // want `init clause spans 3 lines`
+		1,
+	)
+	if err != nil {
+		_ = v
+	}
+}
+
+// Safe: "_" declares nothing and err is fresh.
+func blankAndFresh() {
+	_, err := multi( // want `init clause spans 3 lines`
+		1,
+	)
+	if err != nil {
+		_ = err
+	}
+}
+
+// Safe: "=" assigns to an existing variable; it declares nothing at all.
+func plainAssign() error {
+	var err error
+
+	err = do( // want `init clause spans 3 lines`
+		1,
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// Unsafe: err already exists in the enclosing block. Hoisting the ":=" would
+// assign to that err rather than declaring a new one, so the returned error
+// would silently change.
+func shadowsExistingLocal() error {
+	v, err := multi(1)
+	if err != nil {
+		return err
+	}
+	_ = v
+
+	if v2, err := multi( // want `init clause spans 3 lines`
+		2,
+	); err != nil {
+		_ = v2
+	}
+
+	return err
+}
+
+// Unsafe: the same names are redeclared later in this block, so hoisting turns
+// the later ":=" into "no new variables on left side of :=".
+func declaredLaterInBlock() {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+
+	v, err := multi(2)
+	_, _ = v, err
+}
+
+// Unsafe: err is a parameter, so hoisting would rebind it for the rest of the body.
+func shadowsParam(err error) {
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}
+
+// Conservatively refused: shadowing a package-level name. Nothing reads errState
+// after the if here, so this one would in fact be safe -- the check does not try
+// to prove that.
+func shadowsPackageLevel() {
+	if v, errState := multi( // want `init clause spans 3 lines`
+		1,
+	); errState != nil {
+		_ = v
+	}
+}

pkg/ifinit/testdata/src/cases/structural.go

@@ -0,0 +1,113 @@
+package cases
+
+func multi(args ...int) (int, error) { return 0, nil }
+
+func single() (int, error) { return 0, nil }
+
+func count(args ...int) int { return 0 }
+
+func clean() {
+	if v, err := single(); err != nil {
+		_ = v
+	}
+
+	x := count(
+		1,
+		2,
+	)
+	if x > 0 {
+		_ = x
+	}
+}
+
+func multiLineInit() {
+	if v, err := multi( // want `init clause spans 4 lines`
+		1,
+		2,
+	); err != nil {
+		_ = v
+	}
+}
+
+func elseIfChain() {
+	if x := count(1); x > 0 {
+		_ = x
+	} else if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}
+
+func nestedInsideBody() {
+	if true {
+		if v, err := multi( // want `init clause spans 3 lines`
+			1,
+		); err != nil {
+			_ = v
+		}
+	}
+}
+
+// Only "if" init clauses are covered; for and switch are deliberately untouched.
+func otherInitClauses() {
+	for i := count(
+		1,
+	); i < 10; i++ {
+		_ = i
+	}
+
+	switch v := count(
+		1,
+	); v {
+	case 1:
+	}
+}
+
+func doSomething(args ...int) error { return nil }
+
+func setup(args ...int) {}
+
+// The line break falls after ":=" rather than inside the call's arguments.
+func brokenAfterAssignOp() {
+	if result, err := // want `init clause spans 2 lines`
+		multi(1, 2); err != nil {
+		_ = result
+	}
+}
+
+// Assignment to an existing variable rather than a definition.
+func assignNotDefine() error {
+	var err error
+	if err = doSomething( // want `init clause spans 4 lines`
+		1,
+		2,
+	); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// The init clause is a bare call expression, not an assignment at all.
+func exprStmtInit(condition bool) {
+	if setup( // want `init clause spans 4 lines`
+		1,
+		2,
+	); condition {
+		_ = condition
+	}
+}
+
+// gofmt joins "else" and "if", but the parser accepts them on separate lines --
+// and then the "if" really is the first token on its line. Hoisting here would
+// emit "} v, err := multi(...)", which does not compile.
+func elseOnItsOwnLine() {
+	if true {
+	} else
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}

pkg/ifinit/testdata/src/cases/structural.go.golden

@@ -0,0 +1,118 @@
+package cases
+
+func multi(args ...int) (int, error) { return 0, nil }
+
+func single() (int, error) { return 0, nil }
+
+func count(args ...int) int { return 0 }
+
+func clean() {
+	if v, err := single(); err != nil {
+		_ = v
+	}
+
+	x := count(
+		1,
+		2,
+	)
+	if x > 0 {
+		_ = x
+	}
+}
+
+func multiLineInit() {
+	v, err := multi( // want `init clause spans 4 lines`
+		1,
+		2,
+	)
+	if err != nil {
+		_ = v
+	}
+}
+
+func elseIfChain() {
+	if x := count(1); x > 0 {
+		_ = x
+	} else if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}
+
+func nestedInsideBody() {
+	if true {
+		v, err := multi( // want `init clause spans 3 lines`
+			1,
+		)
+		if err != nil {
+			_ = v
+		}
+	}
+}
+
+// Only "if" init clauses are covered; for and switch are deliberately untouched.
+func otherInitClauses() {
+	for i := count(
+		1,
+	); i < 10; i++ {
+		_ = i
+	}
+
+	switch v := count(
+		1,
+	); v {
+	case 1:
+	}
+}
+
+func doSomething(args ...int) error { return nil }
+
+func setup(args ...int) {}
+
+// The line break falls after ":=" rather than inside the call's arguments.
+func brokenAfterAssignOp() {
+	result, err := // want `init clause spans 2 lines`
+		multi(1, 2)
+	if err != nil {
+		_ = result
+	}
+}
+
+// Assignment to an existing variable rather than a definition.
+func assignNotDefine() error {
+	var err error
+	err = doSomething( // want `init clause spans 4 lines`
+		1,
+		2,
+	)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+// The init clause is a bare call expression, not an assignment at all.
+func exprStmtInit(condition bool) {
+	setup( // want `init clause spans 4 lines`
+		1,
+		2,
+	)
+	if condition {
+		_ = condition
+	}
+}
+
+// gofmt joins "else" and "if", but the parser accepts them on separate lines --
+// and then the "if" really is the first token on its line. Hoisting here would
+// emit "} v, err := multi(...)", which does not compile.
+func elseOnItsOwnLine() {
+	if true {
+	} else
+	if v, err := multi( // want `init clause spans 3 lines`
+		1,
+	); err != nil {
+		_ = v
+	}
+}