fix: reset rewritten state for no-decl files

code/rewriter.go

@@ -594,6 +594,10 @@ func (r *Rewriter) rewriteFuncDecl(fn *ast.FuncDecl) error {
 
 // RewriteFile rewrites a single file
 func (r *Rewriter) RewriteFile(path string) (err error) {
+	// Reset state up front so previous-file result does not leak into
+	// files that have nothing to rewrite (for example, doc.go).
+	r.rewritten = false
+
 	defer func() {
 		if e := recover(); e != nil {
 			err = fmt.Errorf("%s %v\n%s", r.currentPath, e, debug.Stack())
@@ -610,7 +614,6 @@ func (r *Rewriter) RewriteFile(path string) (err error) {
 	r.currentPath = path
 	r.currentFile = file
 	r.currsetFset = fset
-	r.rewritten = false
 
 	var failpointImport *ast.ImportSpec
 	for _, imp := range file.Imports {

code/rewriter_state_test.go

@@ -0,0 +1,44 @@
+package code_test
+
+import (
+	"bytes"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/pingcap/failpoint/code"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRewriteFileResetRewrittenStateForNoDeclFile(t *testing.T) {
+	t.Parallel()
+
+	workDir := t.TempDir()
+	failpointFile := filepath.Join(workDir, "with_failpoint.go")
+	docFile := filepath.Join(workDir, "doc.go")
+
+	require.NoError(t, os.WriteFile(failpointFile, []byte(`package sample
+
+import "github.com/pingcap/failpoint"
+
+func f() {
+	failpoint.Inject("fp", func() {})
+}
+`), 0o644))
+	require.NoError(t, os.WriteFile(docFile, []byte("package sample\n"), 0o644))
+
+	rewriter := code.NewRewriter(workDir)
+	rewriter.SetAllowNotChecked(true)
+
+	var out bytes.Buffer
+
+	rewriter.SetOutput(&out)
+	require.NoError(t, rewriter.RewriteFile(failpointFile))
+	require.True(t, rewriter.GetRewritten())
+
+	out.Reset()
+	rewriter.SetOutput(&out)
+	require.NoError(t, rewriter.RewriteFile(docFile))
+	require.False(t, rewriter.GetRewritten())
+	require.Zero(t, out.Len())
+}