optimization: new optimization for fmt.Errorf("constant")

Author: catenacyber

analyzer/analyzer.go

@@ -35,14 +35,15 @@ func New() *analysis.Analyzer {
 }
 
 func (n *perfSprint) run(pass *analysis.Pass) (interface{}, error) {
-	var fmtSprintObj, fmtSprintfObj types.Object
+	var fmtSprintObj, fmtSprintfObj, fmtErrorfObj types.Object
 	for _, pkg := range pass.Pkg.Imports() {
 		if pkg.Path() == "fmt" {
 			fmtSprintObj = pkg.Scope().Lookup("Sprint")
 			fmtSprintfObj = pkg.Scope().Lookup("Sprintf")
+			fmtErrorfObj = pkg.Scope().Lookup("Errorf")
 		}
 	}
-	if fmtSprintfObj == nil {
+	if fmtSprintfObj == nil && fmtSprintObj == nil && fmtErrorfObj == nil {
 		return nil, nil
 	}
 
@@ -65,6 +66,11 @@ func (n *perfSprint) run(pass *analysis.Pass) (interface{}, error) {
 			err   error
 		)
 		switch {
+		case calledObj == fmtErrorfObj && len(call.Args) == 1:
+			fn = "fmt.Errorf"
+			verb = "%s"
+			value = call.Args[0]
+
 		case calledObj == fmtSprintObj && len(call.Args) == 1:
 			fn = "fmt.Sprint"
 			verb = "%v"
@@ -100,7 +106,7 @@ func (n *perfSprint) run(pass *analysis.Pass) (interface{}, error) {
 
 		var d *analysis.Diagnostic
 		switch {
-		case isBasicType(valueType, types.String) && oneOf(verb, "%v", "%s"):
+		case isBasicType(valueType, types.String) && oneOf(verb, "%v", "%s") && fn != "fmt.Errorf":
 			d = &analysis.Diagnostic{
 				Pos:     call.Pos(),
 				End:     call.End(),
@@ -117,6 +123,23 @@ func (n *perfSprint) run(pass *analysis.Pass) (interface{}, error) {
 				},
 			}
 
+		case isBasicType(valueType, types.String) && oneOf(verb, "%v", "%s") && fn == "fmt.Errorf":
+			d = &analysis.Diagnostic{
+				Pos:     call.Pos(),
+				End:     call.End(),
+				Message: fn + " can be replaced with errors.New",
+				SuggestedFixes: []analysis.SuggestedFix{
+					{
+						Message: "Use errors.New",
+						TextEdits: []analysis.TextEdit{{
+							Pos:     call.Pos(),
+							End:     value.Pos(),
+							NewText: []byte("errors.New("),
+						}},
+					},
+				},
+			}
+
 		case types.Implements(valueType, errIface) && oneOf(verb, "%v", "%s"):
 			errMethodCall := formatNode(pass.Fset, value) + ".Error()"
 			d = &analysis.Diagnostic{

analyzer/replacements_bench_test.go

@@ -3,6 +3,7 @@ package analyzer_test
 import (
 	"context"
 	"encoding/hex"
+	"errors"
 	"fmt"
 	"math"
 	"strconv"
@@ -49,6 +50,20 @@ func BenchmarkErrorFormatting(b *testing.B) {
 	})
 }
 
+func BenchmarkFormattingError(b *testing.B) {
+	b.Run("fmt.Errorf", func(b *testing.B) {
+		for n := 0; n < b.N; n++ {
+			_ = fmt.Errorf("onlystring")
+		}
+	})
+
+	b.Run("errors.New", func(b *testing.B) {
+		for n := 0; n < b.N; n++ {
+			_ = errors.New("onlystring")
+		}
+	})
+}
+
 func BenchmarkBoolFormatting(b *testing.B) {
 	b.Run("fmt.Sprint", func(b *testing.B) {
 		for n := 0; n < b.N; n++ {

analyzer/testdata/src/p/p.go

@@ -20,6 +20,7 @@ func positive() {
 	fmt.Sprintf("%s", s)       // want "fmt.Sprintf can be replaced with just using the string"
 	fmt.Sprintf("%v", s)       // want "fmt.Sprintf can be replaced with just using the string"
 	fmt.Sprint(s)              // want "fmt.Sprint can be replaced with just using the string"
+	fmt.Errorf("hello")        // want "fmt.Errorf can be replaced with errors.New"
 
 	var err error
 	fmt.Sprintf("%s", errSentinel) // want "fmt.Sprintf can be replaced with errSentinel.Error()"
@@ -180,6 +181,7 @@ func negative() {
 	fmt.Printf("%v")
 	fmt.Printf("%d", 42)
 	fmt.Printf("%s %d", "hello", 42)
+	fmt.Errorf("this is %s", "complex")
 
 	fmt.Fprint(os.Stdout, "%d", 42)
 	fmt.Fprintf(os.Stdout, "test")

analyzer/testdata/src/p/p.go.golden

@@ -14,12 +14,13 @@ var errSentinel = errors.New("connection refused")
 
 func positive() {
 	var s string
-	"hello" // want "fmt.Sprintf can be replaced with just using the string"
-	"hello" // want "fmt.Sprintf can be replaced with just using the string"
-	"hello" // want "fmt.Sprint can be replaced with just using the string"
-	s       // want "fmt.Sprintf can be replaced with just using the string"
-	s       // want "fmt.Sprintf can be replaced with just using the string"
-	s       // want "fmt.Sprint can be replaced with just using the string"
+	"hello"             // want "fmt.Sprintf can be replaced with just using the string"
+	"hello"             // want "fmt.Sprintf can be replaced with just using the string"
+	"hello"             // want "fmt.Sprint can be replaced with just using the string"
+	s                   // want "fmt.Sprintf can be replaced with just using the string"
+	s                   // want "fmt.Sprintf can be replaced with just using the string"
+	s                   // want "fmt.Sprint can be replaced with just using the string"
+	errors.New("hello") // want "fmt.Errorf can be replaced with errors.New"
 
 	var err error
 	errSentinel.Error() // want "fmt.Sprintf can be replaced with errSentinel.Error()"
@@ -180,6 +181,7 @@ func negative() {
 	fmt.Printf("%v")
 	fmt.Printf("%d", 42)
 	fmt.Printf("%s %d", "hello", 42)
+	fmt.Errorf("this is %s", "complex")
 
 	fmt.Fprint(os.Stdout, "%d", 42)
 	fmt.Fprintf(os.Stdout, "test")