Update error-strings rule (#608) (#609)

Co-authored-by: SalvadorC <salvadorcavadini+github@gmail.com>

rule/error-strings.go

@@ -17,10 +17,25 @@ type ErrorStringsRule struct{}
 func (r *ErrorStringsRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
 	var failures []lint.Failure
 
+	var errorFunctions = map[string]map[string]struct{}{
+		"fmt": {
+			"Errorf": {},
+		},
+		"errors": {
+			"Errorf":       {},
+			"WithMessage":  {},
+			"Wrap":         {},
+			"New":          {},
+			"WithMessagef": {},
+			"Wrapf":        {},
+		},
+	}
+
 	fileAst := file.AST
 	walker := lintErrorStrings{
-		file:    file,
-		fileAst: fileAst,
+		file:           file,
+		fileAst:        fileAst,
+		errorFunctions: errorFunctions,
 		onFailure: func(failure lint.Failure) {
 			failures = append(failures, failure)
 		},
@@ -37,24 +52,31 @@ func (r *ErrorStringsRule) Name() string {
 }
 
 type lintErrorStrings struct {
-	file      *lint.File
-	fileAst   *ast.File
-	onFailure func(lint.Failure)
+	file           *lint.File
+	fileAst        *ast.File
+	errorFunctions map[string]map[string]struct{}
+	onFailure      func(lint.Failure)
 }
 
+// Visit browses the AST
 func (w lintErrorStrings) Visit(n ast.Node) ast.Visitor {
 	ce, ok := n.(*ast.CallExpr)
 	if !ok {
 		return w
 	}
-	if !isPkgDot(ce.Fun, "errors", "New") && !isPkgDot(ce.Fun, "fmt", "Errorf") {
-		return w
-	}
+
 	if len(ce.Args) < 1 {
 		return w
 	}
-	str, ok := ce.Args[0].(*ast.BasicLit)
-	if !ok || str.Kind != token.STRING {
+
+	// expression matches the known pkg.function
+	ok = w.match(ce)
+	if !ok {
+		return w
+	}
+
+	str, ok := w.getMessage(ce)
+	if !ok {
 		return w
 	}
 	s, _ := strconv.Unquote(str.Value) // can assume well-formed Go
@@ -65,7 +87,6 @@ func (w lintErrorStrings) Visit(n ast.Node) ast.Visitor {
 	if clean {
 		return w
 	}
-
 	w.onFailure(lint.Failure{
 		Node:       str,
 		Confidence: conf,
@@ -75,6 +96,52 @@ func (w lintErrorStrings) Visit(n ast.Node) ast.Visitor {
 	return w
 }
 
+// match returns true if the expression corresponds to the known pkg.function
+// i.e.: errors.Wrap
+func (w lintErrorStrings) match(expr *ast.CallExpr) bool {
+	sel, ok := expr.Fun.(*ast.SelectorExpr)
+	if !ok {
+		return false
+	}
+	// retrieve the package
+	id, ok := sel.X.(*ast.Ident)
+	functions, ok := w.errorFunctions[id.Name]
+	if !ok {
+		return false
+	}
+	// retrieve the function
+	_, ok = functions[sel.Sel.Name]
+	return ok
+}
+
+// getMessage returns the message depending on its position
+// returns false if the cast is unsuccessful
+func (w lintErrorStrings) getMessage(expr *ast.CallExpr) (s *ast.BasicLit, success bool) {
+	str, ok := w.checkArg(expr, 0)
+	if ok {
+		return str, true
+	}
+	if len(expr.Args) < 2 {
+		return s, false
+	}
+	str, ok = w.checkArg(expr, 1)
+	if !ok {
+		return s, false
+	}
+	return str, true
+}
+
+func (lintErrorStrings) checkArg(expr *ast.CallExpr, arg int) (s *ast.BasicLit, success bool) {
+	str, ok := expr.Args[arg].(*ast.BasicLit)
+	if !ok {
+		return s, false
+	}
+	if str.Kind != token.STRING {
+		return s, false
+	}
+	return str, true
+}
+
 func lintErrorString(s string) (isClean bool, conf float64) {
 	const basicConfidence = 0.8
 	const capConfidence = basicConfidence - 0.2

testdata/golint/error-strings-pkg-errors.go

@@ -0,0 +1,18 @@
+// Package foo ...
+package foo
+
+import (
+	"github.com/pkg/errors"
+)
+
+// Check for the error strings themselves.
+
+func errorsStrings(x int) error {
+	var err error
+	err = errors.Wrap(err, "This %d is too low")            // MATCH /error strings should not be capitalized or end with punctuation or a newline/
+	err = errors.New("This %d is too low")                  // MATCH /error strings should not be capitalized or end with punctuation or a newline/
+	err = errors.Wrapf(err, "This %d is too low", x)        // MATCH /error strings should not be capitalized or end with punctuation or a newline/
+	err = errors.WithMessage(err, "This %d is too low")     // MATCH /error strings should not be capitalized or end with punctuation or a newline/
+	err = errors.WithMessagef(err, "This %d is too low", x) // MATCH /error strings should not be capitalized or end with punctuation or a newline/
+	return err
+}