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- package rule
-
- import (
- "go/ast"
- "go/token"
- "strings"
-
- "github.com/mgechev/revive/lint"
- )
-
- // IfReturnRule lints given else constructs.
- type IfReturnRule struct{}
-
- // Apply applies the rule to given file.
- func (r *IfReturnRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
- var failures []lint.Failure
-
- onFailure := func(failure lint.Failure) {
- failures = append(failures, failure)
- }
-
- astFile := file.AST
- w := &lintElseError{astFile, onFailure}
- ast.Walk(w, astFile)
- return failures
- }
-
- // Name returns the rule name.
- func (r *IfReturnRule) Name() string {
- return "if-return"
- }
-
- type lintElseError struct {
- file *ast.File
- onFailure func(lint.Failure)
- }
-
- func (w *lintElseError) Visit(node ast.Node) ast.Visitor {
- switch v := node.(type) {
- case *ast.BlockStmt:
- for i := 0; i < len(v.List)-1; i++ {
- // if var := whatever; var != nil { return var }
- s, ok := v.List[i].(*ast.IfStmt)
- if !ok || s.Body == nil || len(s.Body.List) != 1 || s.Else != nil {
- continue
- }
- assign, ok := s.Init.(*ast.AssignStmt)
- if !ok || len(assign.Lhs) != 1 || !(assign.Tok == token.DEFINE || assign.Tok == token.ASSIGN) {
- continue
- }
- id, ok := assign.Lhs[0].(*ast.Ident)
- if !ok {
- continue
- }
- expr, ok := s.Cond.(*ast.BinaryExpr)
- if !ok || expr.Op != token.NEQ {
- continue
- }
- if lhs, ok := expr.X.(*ast.Ident); !ok || lhs.Name != id.Name {
- continue
- }
- if rhs, ok := expr.Y.(*ast.Ident); !ok || rhs.Name != "nil" {
- continue
- }
- r, ok := s.Body.List[0].(*ast.ReturnStmt)
- if !ok || len(r.Results) != 1 {
- continue
- }
- if r, ok := r.Results[0].(*ast.Ident); !ok || r.Name != id.Name {
- continue
- }
-
- // return nil
- r, ok = v.List[i+1].(*ast.ReturnStmt)
- if !ok || len(r.Results) != 1 {
- continue
- }
- if r, ok := r.Results[0].(*ast.Ident); !ok || r.Name != "nil" {
- continue
- }
-
- // check if there are any comments explaining the construct, don't emit an error if there are some.
- if containsComments(s.Pos(), r.Pos(), w.file) {
- continue
- }
-
- w.onFailure(lint.Failure{
- Confidence: .9,
- Node: v.List[i],
- Failure: "redundant if ...; err != nil check, just return error instead.",
- })
- }
- }
- return w
- }
-
- func containsComments(start, end token.Pos, f *ast.File) bool {
- for _, cgroup := range f.Comments {
- comments := cgroup.List
- if comments[0].Slash >= end {
- // All comments starting with this group are after end pos.
- return false
- }
- if comments[len(comments)-1].Slash < start {
- // Comments group ends before start pos.
- continue
- }
- for _, c := range comments {
- if start <= c.Slash && c.Slash < end && !strings.HasPrefix(c.Text, "// MATCH ") {
- return true
- }
- }
- }
- return false
- }
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