Improve fixer performance

By `Prepare`ing the linter before repeated use.

```
150116720 ns/op  101567417 B/op   2359322 allocs/op // Before
132816578 ns/op   89093239 B/op   2068892 allocs/op // After
```

Signed-off-by: Anders Eknert <anders.eknert@apple.com>

Author: anderseknert

pkg/fixer/fixer.go

@@ -26,7 +26,7 @@ const (
 
 // Fixer must be instantiated via NewFixer.
 type Fixer struct {
-	registeredFixes     map[string]any
+	registeredFixes     map[string]fixes.Fix
 	onConflictOperation OnConflictOperation
 	registeredRoots     []string
 	versionsMap         map[string]ast.RegoVersion
@@ -35,7 +35,7 @@ type Fixer struct {
 // NewFixer instantiates a Fixer.
 func NewFixer() *Fixer {
 	return &Fixer{
-		registeredFixes:     make(map[string]any),
+		registeredFixes:     make(map[string]fixes.Fix),
 		registeredRoots:     make([]string, 0),
 		onConflictOperation: OnConflictError,
 	}
@@ -78,17 +78,11 @@ func (f *Fixer) RegisterRoots(roots ...string) *Fixer {
 }
 
 func (f *Fixer) GetFixForName(name string) (fixes.Fix, bool) {
-	fix, ok := f.registeredFixes[name]
-	if !ok {
-		return nil, false
+	if fix, ok := f.registeredFixes[name]; ok {
+		return fix, true
 	}
 
-	fixInstance, ok := fix.(fixes.Fix)
-	if !ok {
-		return nil, false
-	}
-
-	return fixInstance, true
+	return nil, false
 }
 
 func (f *Fixer) Fix(ctx context.Context, l *linter.Linter, fp fileprovider.FileProvider) (*Report, error) {
@@ -119,16 +113,13 @@ func (f *Fixer) FixViolations(
 		return nil, fmt.Errorf("failed to list files: %w", err)
 	}
 
-	// rangeValCopy may be expensive, but this is not critical enough
-	// to motivate cluttering the code
-	//nolint:gocritic
-	for _, violation := range violations {
-		fixInstance, ok := f.GetFixForName(violation.Title)
+	for i := range violations {
+		fixInstance, ok := f.GetFixForName(violations[i].Title)
 		if !ok {
-			return nil, fmt.Errorf("no fix for violation %s", violation.Title)
+			return nil, fmt.Errorf("no fix for violation %s", violations[i].Title)
 		}
 
-		file := violation.Location.File
+		file := violations[i].Location.File
 
 		fc, err := fp.Get(file)
 		if err != nil {
@@ -143,7 +134,7 @@ func (f *Fixer) FixViolations(
 		fixResults, err := fixInstance.Fix(&fixes.FixCandidate{Filename: file, Contents: fc}, &fixes.RuntimeOptions{
 			BaseDir:   util.FindClosestMatchingRoot(abs, f.registeredRoots),
 			Config:    config,
-			Locations: []report.Location{violation.Location},
+			Locations: []report.Location{violations[i].Location},
 		})
 		if err != nil {
 			return nil, fmt.Errorf("failed to fix %s: %w", file, err)
@@ -200,6 +191,11 @@ func (f *Fixer) applyLinterFixes(
 		versionsMap = f.versionsMap
 	}
 
+	li, err := l.WithDisableAll(true).WithEnabledRules(fixableEnabledRules...).Prepare(ctx)
+	if err != nil {
+		return fmt.Errorf("failed to prepare linter for fixing: %w", err)
+	}
+
 	for {
 		fixMadeInIteration := false
 
@@ -208,7 +204,7 @@ func (f *Fixer) applyLinterFixes(
 			return fmt.Errorf("failed to create linter input: %w", err)
 		}
 
-		rep, err := l.WithDisableAll(true).WithEnabledRules(fixableEnabledRules...).WithInputModules(&in).Lint(ctx)
+		rep, err := li.WithInputModules(&in).Lint(ctx)
 		if err != nil {
 			return fmt.Errorf("failed to lint before fixing: %w", err)
 		}
@@ -217,19 +213,18 @@ func (f *Fixer) applyLinterFixes(
 			break
 		}
 
-		//nolint:gocritic
-		for _, violation := range rep.Violations {
-			fixInstance, ok := f.GetFixForName(violation.Title)
+		for i := range rep.Violations {
+			fixInstance, ok := f.GetFixForName(rep.Violations[i].Title)
 			if !ok {
-				return fmt.Errorf("no fix for violation %s", violation.Title)
+				return fmt.Errorf("no fix for violation %s", rep.Violations[i].Title)
 			}
 
 			config, err := l.GetConfig()
 			if err != nil {
 				return fmt.Errorf("failed to get config: %w", err)
 			}
 
-			file := violation.Location.File
+			file := rep.Violations[i].Location.File
 
 			abs, err := filepath.Abs(file)
 			if err != nil {
@@ -246,7 +241,7 @@ func (f *Fixer) applyLinterFixes(
 			fixResults, err := fixInstance.Fix(&fixCandidate, &fixes.RuntimeOptions{
 				BaseDir:   util.FindClosestMatchingRoot(abs, f.registeredRoots),
 				Config:    config,
-				Locations: []report.Location{violation.Location},
+				Locations: []report.Location{rep.Violations[i].Location},
 			})
 			if err != nil {
 				return fmt.Errorf("failed to fix %s: %w", file, err)
@@ -259,7 +254,7 @@ func (f *Fixer) applyLinterFixes(
 			fixResult := fixResults[0]
 
 			if fixResult.Rename != nil {
-				if err = f.handleRename(fp, fixReport, startingFiles, fixResult); err != nil {
+				if err := f.handleRename(fp, fixReport, startingFiles, fixResult); err != nil {
 					return err
 				}
 

pkg/fixer/fixer_test.go

@@ -34,9 +34,7 @@ deny = true
 
 	memfp := fileprovider.NewInMemoryFileProvider(policies)
 
-	input, err := memfp.ToInput(map[string]ast.RegoVersion{
-		mainDir: ast.RegoV1,
-	})
+	input, err := memfp.ToInput(map[string]ast.RegoVersion{mainDir: ast.RegoV1})
 	if err != nil {
 		t.Fatalf("failed to create input: %v", err)
 	}
@@ -196,3 +194,39 @@ func TestFixViolations(t *testing.T) {
 		}
 	}
 }
+
+// 150116720 ns/op  101567417 B/op   2359322 allocs/op
+// 132816578 ns/op   89093239 B/op   2068892 allocs/op // Linter.Prepare()
+func BenchmarkFixViolations(b *testing.B) {
+	rootPath := testutil.Must(filepath.Abs(filepath.FromSlash("/root")))(b)
+	mainDir := filepath.Join(rootPath, "main")
+	mainRegoFile := filepath.Join(mainDir, "main.rego")
+
+	policies := map[string]string{
+		mainRegoFile: `package test
+
+allow if {
+true #no space
+}
+deny = true
+`,
+	}
+
+	memfp := fileprovider.NewInMemoryFileProvider(policies)
+
+	input, err := memfp.ToInput(map[string]ast.RegoVersion{mainDir: ast.RegoV1})
+	if err != nil {
+		b.Fatalf("failed to create input: %v", err)
+	}
+
+	l := linter.NewLinter().WithEnableAll(true).WithInputModules(&input)
+	f := NewFixer().RegisterFixes(fixes.NewDefaultFixes()...).RegisterRoots(rootPath).
+		SetRegoVersionsMap(map[string]ast.RegoVersion{mainDir: ast.RegoV1})
+
+	for b.Loop() {
+		_, err := f.Fix(b.Context(), &l, memfp)
+		if err != nil {
+			b.Fatalf("failed to fix: %v", err)
+		}
+	}
+}

pkg/fixer/fixes/nowhitespacecomment.go

@@ -20,7 +20,7 @@ func (n *NoWhitespaceComment) Fix(fc *FixCandidate, opts *RuntimeOptions) ([]Fix
 	fixed := false
 
 	for _, loc := range opts.Locations {
-		if loc.Row > len(lines) || loc.Column > len(lines[loc.Row-1]) || loc.Column < 1 {
+		if loc.Row < 1 || loc.Column < 1 || loc.Row > len(lines) || loc.Column > len(lines[loc.Row-1]) {
 			continue
 		}
 

pkg/linter/linter.go

@@ -388,6 +388,10 @@ func (l Linter) Lint(ctx context.Context) (report.Report, error) {
 		l.stopTimer(regalmetrics.RegalFilterIgnoredModules)
 	}
 
+	if len(l.inputPaths) == 0 && l.inputModules == nil && len(l.overriddenAggregates) == 0 {
+		return report.Report{}, errors.New("nothing provided to lint")
+	}
+
 	regoReport, err := l.lint(ctx, input)
 	if err != nil {
 		return report.Report{}, fmt.Errorf("failed to lint using Rego rules: %w", err)
@@ -531,10 +535,6 @@ func (l Linter) notPrepared() Linter {
 }
 
 func (l Linter) validate(conf *config.Config) error {
-	if len(l.inputPaths) == 0 && l.inputModules == nil && len(l.overriddenAggregates) == 0 {
-		return errors.New("nothing provided to lint")
-	}
-
 	if l.customRuleError != nil {
 		return fmt.Errorf("failed to load custom rules: %w", l.customRuleError)
 	}