x/tools: use ast.IsGenerated throughout

Note the behavior change: the go/ast implementation
checks that the special comment appears before the
packge declaration; the ad hoc implementations did not.

Change-Id: Ib51c498c1c73fd32c882e25f8228a6076bba7ed7
Reviewed-on: https://go-review.googlesource.com/c/tools/+/649316
LUCI-TryBot-Result: Go LUCI <[email protected]>
Auto-Submit: Alan Donovan <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>
Commit-Queue: Alan Donovan <[email protected]>

Author: adonovan

cmd/deadcode/deadcode.go

@@ -175,7 +175,7 @@ func main() {
 				}
 			}
 
-			if isGenerated(file) {
+			if ast.IsGenerated(file) {
 				generated[p.Fset.File(file.Pos()).Name()] = true
 			}
 		}
@@ -414,45 +414,6 @@ func printObjects(format string, objects []any) {
 	}
 }
 
-// TODO(adonovan): use go1.21's ast.IsGenerated.
-
-// isGenerated reports whether the file was generated by a program,
-// not handwritten, by detecting the special comment described
-// at https://go.dev/s/generatedcode.
-//
-// The syntax tree must have been parsed with the ParseComments flag.
-// Example:
-//
-//	f, err := parser.ParseFile(fset, filename, src, parser.ParseComments|parser.PackageClauseOnly)
-//	if err != nil { ... }
-//	gen := ast.IsGenerated(f)
-func isGenerated(file *ast.File) bool {
-	_, ok := generator(file)
-	return ok
-}
-
-func generator(file *ast.File) (string, bool) {
-	for _, group := range file.Comments {
-		for _, comment := range group.List {
-			if comment.Pos() > file.Package {
-				break // after package declaration
-			}
-			// opt: check Contains first to avoid unnecessary array allocation in Split.
-			const prefix = "// Code generated "
-			if strings.Contains(comment.Text, prefix) {
-				for _, line := range strings.Split(comment.Text, "\n") {
-					if rest, ok := strings.CutPrefix(line, prefix); ok {
-						if gen, ok := strings.CutSuffix(rest, " DO NOT EDIT."); ok {
-							return gen, true
-						}
-					}
-				}
-			}
-		}
-	}
-	return "", false
-}
-
 // pathSearch returns the shortest path from one of the roots to one
 // of the targets (along with the root itself), or zero if no path was found.
 func pathSearch(roots []*ssa.Function, res *rta.Result, targets map[*ssa.Function]bool) (*callgraph.Node, []*callgraph.Edge) {

copyright/copyright.go

@@ -75,7 +75,7 @@ func checkFile(toolsDir, filename string) (bool, error) {
 		return false, err
 	}
 	// Don't require headers on generated files.
-	if isGenerated(fset, parsed) {
+	if ast.IsGenerated(parsed) {
 		return false, nil
 	}
 	shouldAddCopyright := true
@@ -91,24 +91,3 @@ func checkFile(toolsDir, filename string) (bool, error) {
 	}
 	return shouldAddCopyright, nil
 }
-
-// Copied from golang.org/x/tools/gopls/internal/golang/util.go.
-// Matches cgo generated comment as well as the proposed standard:
-//
-//	https://golang.org/s/generatedcode
-var generatedRx = regexp.MustCompile(`// .*DO NOT EDIT\.?`)
-
-func isGenerated(fset *token.FileSet, file *ast.File) bool {
-	for _, commentGroup := range file.Comments {
-		for _, comment := range commentGroup.List {
-			if matched := generatedRx.MatchString(comment.Text); !matched {
-				continue
-			}
-			// Check if comment is at the beginning of the line in source.
-			if pos := fset.Position(comment.Slash); pos.Column == 1 {
-				return true
-			}
-		}
-	}
-	return false
-}

gopls/internal/golang/format.go

@@ -35,15 +35,16 @@ func Format(ctx context.Context, snapshot *cache.Snapshot, fh file.Handle) ([]pr
 	ctx, done := event.Start(ctx, "golang.Format")
 	defer done()
 
-	// Generated files shouldn't be edited. So, don't format them
-	if IsGenerated(ctx, snapshot, fh.URI()) {
-		return nil, fmt.Errorf("can't format %q: file is generated", fh.URI().Path())
-	}
-
 	pgf, err := snapshot.ParseGo(ctx, fh, parsego.Full)
 	if err != nil {
 		return nil, err
 	}
+
+	// Generated files shouldn't be edited. So, don't format them.
+	if ast.IsGenerated(pgf.File) {
+		return nil, fmt.Errorf("can't format %q: file is generated", fh.URI().Path())
+	}
+
 	// Even if this file has parse errors, it might still be possible to format it.
 	// Using format.Node on an AST with errors may result in code being modified.
 	// Attempt to format the source of this file instead.

gopls/internal/golang/util.go

@@ -19,16 +19,11 @@ import (
 	"golang.org/x/tools/gopls/internal/cache/parsego"
 	"golang.org/x/tools/gopls/internal/protocol"
 	"golang.org/x/tools/gopls/internal/util/bug"
-	"golang.org/x/tools/gopls/internal/util/safetoken"
 	"golang.org/x/tools/internal/tokeninternal"
 )
 
-// IsGenerated gets and reads the file denoted by uri and reports
-// whether it contains a "generated file" comment as described at
-// https://golang.org/s/generatedcode.
-//
-// TODO(adonovan): opt: this function does too much.
-// Move snapshot.ReadFile into the caller (most of which have already done it).
+// IsGenerated reads and parses the header of the file denoted by uri
+// and reports whether it [ast.IsGenerated].
 func IsGenerated(ctx context.Context, snapshot *cache.Snapshot, uri protocol.DocumentURI) bool {
 	fh, err := snapshot.ReadFile(ctx, uri)
 	if err != nil {
@@ -38,17 +33,7 @@ func IsGenerated(ctx context.Context, snapshot *cache.Snapshot, uri protocol.Doc
 	if err != nil {
 		return false
 	}
-	for _, commentGroup := range pgf.File.Comments {
-		for _, comment := range commentGroup.List {
-			if matched := generatedRx.MatchString(comment.Text); matched {
-				// Check if comment is at the beginning of the line in source.
-				if safetoken.Position(pgf.Tok, comment.Slash).Column == 1 {
-					return true
-				}
-			}
-		}
-	}
-	return false
+	return ast.IsGenerated(pgf.File)
 }
 
 // adjustedObjEnd returns the end position of obj, possibly modified for
@@ -76,11 +61,6 @@ func adjustedObjEnd(obj types.Object) token.Pos {
 	return obj.Pos() + token.Pos(nameLen)
 }
 
-// Matches cgo generated comment as well as the proposed standard:
-//
-//	https://golang.org/s/generatedcode
-var generatedRx = regexp.MustCompile(`// .*DO NOT EDIT\.?`)
-
 // FormatNode returns the "pretty-print" output for an ast node.
 func FormatNode(fset *token.FileSet, n ast.Node) string {
 	var buf strings.Builder

gopls/internal/test/integration/diagnostics/diagnostics_test.go

@@ -542,27 +542,34 @@ var X = 0
 
 // Tests golang/go#38467.
 func TestNoSuggestedFixesForGeneratedFiles_Issue38467(t *testing.T) {
+	// This test ensures that gopls' CodeAction handler suppresses
+	// diagnostics in generated code. Beware that many analyzers
+	// themselves suppress diagnostics in generated files, in
+	// particular the low-status "simplifiers" (modernize,
+	// simplify{range,slice,compositelit}), so we use the hostport
+	// analyzer here.
 	const generated = `
 -- go.mod --
 module mod.com
 
 go 1.12
 -- main.go --
+// Code generated by generator.go. DO NOT EDIT.
+
 package main
 
-// Code generated by generator.go. DO NOT EDIT.
+import ("fmt"; "net")
 
 func _() {
-	for i, _ := range []string{} {
-		_ = i
-	}
+	addr := fmt.Sprintf("%s:%d", "localhost", 12345)
+	net.Dial("tcp", addr)
 }
 `
 	Run(t, generated, func(t *testing.T, env *Env) {
 		env.OpenFile("main.go")
 		var d protocol.PublishDiagnosticsParams
 		env.AfterChange(
-			Diagnostics(AtPosition("main.go", 5, 6)),
+			Diagnostics(AtPosition("main.go", 7, 21)),
 			ReadDiagnostics("main.go", &d),
 		)
 		if fixes := env.GetQuickFixes("main.go", d.Diagnostics); len(fixes) != 0 {

gopls/internal/test/marker/testdata/diagnostics/generated.txt

@@ -10,10 +10,10 @@ module example.com
 go 1.12
 
 -- generated.go --
-package generated
-
 // Code generated by generator.go. DO NOT EDIT.
 
+package generated
+
 func _() {
 	var y int //@diag("y", re"declared (and|but) not used")
 }

internal/refactor/inline/inline.go

@@ -102,9 +102,9 @@ func (st *state) inline() (*Result, error) {
 		return nil, fmt.Errorf("internal error: caller syntax positions are inconsistent with file content (did you forget to use FileSet.PositionFor when computing the file name?)")
 	}
 
-	// TODO(adonovan): use go1.21's ast.IsGenerated.
 	// Break the string literal so we can use inlining in this file. :)
-	if bytes.Contains(caller.Content, []byte("// Code generated by "+"cmd/cgo; DO NOT EDIT.")) {
+	if ast.IsGenerated(caller.File) &&
+		bytes.Contains(caller.Content, []byte("// Code generated by "+"cmd/cgo; DO NOT EDIT.")) {
 		return nil, fmt.Errorf("cannot inline calls from files that import \"C\"")
 	}
 

refactor/rename/rename.go

@@ -491,7 +491,7 @@ func (r *renamer) update() error {
 	for _, info := range r.packages {
 		for _, f := range info.Files {
 			tokenFile := r.iprog.Fset.File(f.FileStart)
-			if filesToUpdate[tokenFile] && generated(f, tokenFile) {
+			if filesToUpdate[tokenFile] && ast.IsGenerated(f) {
 				generatedFileNames = append(generatedFileNames, tokenFile.Name())
 			}
 		}

refactor/rename/spec.go

@@ -19,7 +19,6 @@ import (
 	"log"
 	"os"
 	"path/filepath"
-	"regexp"
 	"strconv"
 	"strings"
 
@@ -321,7 +320,7 @@ func findFromObjectsInFile(iprog *loader.Program, spec *spec) ([]types.Object, e
 
 			if spec.offset != 0 {
 				// We cannot refactor generated files since position information is invalidated.
-				if generated(f, thisFile) {
+				if ast.IsGenerated(f) {
 					return nil, fmt.Errorf("cannot rename identifiers in generated file containing DO NOT EDIT marker: %s", thisFile.Name())
 				}
 
@@ -566,25 +565,3 @@ func ambiguityError(fset *token.FileSet, objects []types.Object) error {
 	return fmt.Errorf("ambiguous specifier %s matches %s",
 		objects[0].Name(), buf.String())
 }
-
-// Matches cgo generated comment as well as the proposed standard:
-//
-//	https://golang.org/s/generatedcode
-var generatedRx = regexp.MustCompile(`// .*DO NOT EDIT\.?`)
-
-// generated reports whether ast.File is a generated file.
-func generated(f *ast.File, tokenFile *token.File) bool {
-
-	// Iterate over the comments in the file
-	for _, commentGroup := range f.Comments {
-		for _, comment := range commentGroup.List {
-			if matched := generatedRx.MatchString(comment.Text); matched {
-				// Check if comment is at the beginning of the line in source
-				if pos := tokenFile.Position(comment.Slash); pos.Column == 1 {
-					return true
-				}
-			}
-		}
-	}
-	return false
-}