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error-strings.go
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error-strings.go
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package rule
import (
"go/ast"
"go/token"
"strconv"
"unicode"
"unicode/utf8"
"github.com/mgechev/revive/lint"
)
// ErrorStringsRule lints given else constructs.
type ErrorStringsRule struct{}
// Apply applies the rule to given file.
func (r *ErrorStringsRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
var failures []lint.Failure
var printFunctions = map[string]map[string]struct{}{
"fmt": {
"Errorf": {},
},
"errors": {
"Errorf": {},
"WithMessage": {},
"Wrap": {},
"New": {},
"WithMessagef": {},
"Wrapf": {},
},
}
fileAst := file.AST
walker := lintErrorStrings{
file: file,
fileAst: fileAst,
printFunctions: printFunctions,
onFailure: func(failure lint.Failure) {
failures = append(failures, failure)
},
}
ast.Walk(walker, fileAst)
return failures
}
// Name returns the rule name.
func (r *ErrorStringsRule) Name() string {
return "error-strings"
}
type lintErrorStrings struct {
file *lint.File
fileAst *ast.File
printFunctions 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 len(ce.Args) < 1 {
return w
}
// 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
if s == "" {
return w
}
clean, conf := lintErrorString(s)
if clean {
return w
}
w.onFailure(lint.Failure{
Node: str,
Confidence: conf,
Category: "errors",
Failure: "error strings should not be capitalized or end with punctuation or a newline",
})
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.printFunctions[id.Name]
if !ok {
return false
}
// retrieve the function
_, ok = functions[sel.Sel.Name]
if !ok {
return false
}
return true
}
// getMessage returns the message depending on its position
// returns false if the cast is unsuccessful
func (lintErrorStrings) getMessage(expr *ast.CallExpr) (s *ast.BasicLit, success bool) {
str, ok := checkArg(expr, 0)
if ok {
return str, true
}
if len(expr.Args) < 2 {
return s, false
}
str, ok = checkArg(expr, 1)
if !ok {
return s, false
}
return str, true
}
func 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
first, firstN := utf8.DecodeRuneInString(s)
last, _ := utf8.DecodeLastRuneInString(s)
if last == '.' || last == ':' || last == '!' || last == '\n' {
return false, basicConfidence
}
if unicode.IsUpper(first) {
// People use proper nouns and exported Go identifiers in error strings,
// so decrease the confidence of warnings for capitalization.
if len(s) <= firstN {
return false, capConfidence
}
// Flag strings starting with something that doesn't look like an initialism.
if second, _ := utf8.DecodeRuneInString(s[firstN:]); !unicode.IsUpper(second) {
return false, capConfidence
}
}
return true, 0
}