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