mirror: linter that suggest using alternative string/[]byte functions (…

…#3825)

.golangci.reference.yml

@@ -2140,6 +2140,7 @@ linters:
     - maintidx
     - makezero
     - maligned
+    - mirror
     - misspell
     - musttag
     - nakedret
@@ -2253,6 +2254,7 @@ linters:
     - maintidx
     - makezero
     - maligned
+    - mirror
     - misspell
     - musttag
     - nakedret

go.mod

@@ -24,6 +24,7 @@ require (
 	github.com/breml/bidichk v0.2.4
 	github.com/breml/errchkjson v0.3.1
 	github.com/butuzov/ireturn v0.2.0
+	github.com/butuzov/mirror v1.1.0
 	github.com/charithe/durationcheck v0.0.10
 	github.com/curioswitch/go-reassign v0.2.0
 	github.com/daixiang0/gci v0.10.1

pkg/golinters/mirror.go

@@ -0,0 +1,70 @@
+package golinters
+
+import (
+	"sync"
+
+	"github.com/butuzov/mirror"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+	"github.com/golangci/golangci-lint/pkg/lint/linter"
+	"github.com/golangci/golangci-lint/pkg/result"
+)
+
+func NewMirror() *goanalysis.Linter {
+	var (
+		mu     sync.Mutex
+		issues []goanalysis.Issue
+	)
+
+	a := mirror.NewAnalyzer()
+	a.Run = func(pass *analysis.Pass) (any, error) {
+		// mirror only lints test files if the `--with-tests` flag is passed,
+		// so we pass the `with-tests` flag as true to the analyzer before running it.
+		// This can be turned off by using the regular golangci-lint flags such as `--tests` or `--skip-files`
+		// or can be disabled per linter via exclude rules.
+		// (see https://github.com/golangci/golangci-lint/issues/2527#issuecomment-1023707262)
+		violations := mirror.Run(pass, true)
+
+		if len(violations) == 0 {
+			return nil, nil
+		}
+
+		for index := range violations {
+			i := violations[index].Issue(pass.Fset)
+
+			issue := result.Issue{
+				FromLinter: a.Name,
+				Text:       i.Message,
+				Pos:        i.Start,
+			}
+
+			if len(i.InlineFix) > 0 {
+				issue.Replacement = &result.Replacement{
+					Inline: &result.InlineFix{
+						StartCol:  i.Start.Column - 1,
+						Length:    len(i.Original),
+						NewString: i.InlineFix,
+					},
+				}
+			}
+
+			mu.Lock()
+			issues = append(issues, goanalysis.NewIssue(&issue, pass))
+			mu.Unlock()
+		}
+
+		return nil, nil
+	}
+
+	analyzer := goanalysis.NewLinter(
+		a.Name,
+		a.Doc,
+		[]*analysis.Analyzer{a},
+		nil,
+	).WithIssuesReporter(func(*linter.Context) []goanalysis.Issue {
+		return issues
+	}).WithLoadMode(goanalysis.LoadModeTypesInfo)
+
+	return analyzer
+}

pkg/lint/lintersdb/manager.go

@@ -654,6 +654,12 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 			WithURL("https://github.com/mdempsky/maligned").
 			Deprecated("The repository of the linter has been archived by the owner.", "v1.38.0", "govet 'fieldalignment'"),
 
+		linter.NewConfig(golinters.NewMirror()).
+			WithSince("v1.53.0").
+			WithPresets(linter.PresetStyle).
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/butuzov/mirror"),
+
 		linter.NewConfig(golinters.NewMisspell(misspellCfg)).
 			WithSince("v1.8.0").
 			WithPresets(linter.PresetStyle, linter.PresetComment).

test/testdata/mirror.go

@@ -0,0 +1,12 @@
+//golangcitest:args -Emirror
+package testdata
+
+import (
+	"strings"
+	"unicode/utf8"
+)
+
+func foobar() {
+	_ = utf8.RuneCount([]byte("foobar"))                                                                            // want `avoid allocations with utf8\.RuneCountInString`
+	_ = strings.Compare(string([]byte{'f', 'o', 'o', 'b', 'a', 'r'}), string([]byte{'f', 'o', 'o', 'b', 'a', 'r'})) // want `avoid allocations with bytes\.Compare`
+}