bare-return (first working version) (#117)

New rule bare-return

rule/bare-return.go

@@ -0,0 +1,77 @@
+package rule
+
+import (
+	"go/ast"
+
+	"github.com/mgechev/revive/lint"
+)
+
+// BareReturnRule lints given else constructs.
+type BareReturnRule struct{}
+
+// Apply applies the rule to given file.
+func (r *BareReturnRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
+	var failures []lint.Failure
+
+	onFailure := func(failure lint.Failure) {
+		failures = append(failures, failure)
+	}
+
+	w := lintBareReturnRule{onFailure: onFailure}
+	ast.Walk(w, file.AST)
+	return failures
+}
+
+// Name returns the rule name.
+func (r *BareReturnRule) Name() string {
+	return "bare-return"
+}
+
+type lintBareReturnRule struct {
+	onFailure func(lint.Failure)
+}
+
+func (w lintBareReturnRule) Visit(node ast.Node) ast.Visitor {
+	switch n := node.(type) {
+	case *ast.FuncDecl:
+		w.checkFunc(n.Type.Results, n.Body)
+	case *ast.FuncLit: // to cope with deferred functions and go-routines
+		w.checkFunc(n.Type.Results, n.Body)
+	}
+
+	return w
+}
+
+// checkFunc will verify if the given function has named result and bare returns
+func (w lintBareReturnRule) checkFunc(results *ast.FieldList, body *ast.BlockStmt) {
+	hasNamedResults := results != nil && len(results.List) > 0 && results.List[0].Names != nil
+	if !hasNamedResults || body == nil {
+		return // nothing to do
+	}
+
+	brf := bareReturnFinder{w.onFailure}
+	ast.Walk(brf, body)
+}
+
+type bareReturnFinder struct {
+	onFailure func(lint.Failure)
+}
+
+func (w bareReturnFinder) Visit(node ast.Node) ast.Visitor {
+	rs, ok := node.(*ast.ReturnStmt)
+	if !ok {
+		return w
+	}
+
+	if len(rs.Results) > 0 {
+		return w
+	}
+
+	w.onFailure(lint.Failure{
+		Confidence: 1,
+		Node:       rs,
+		Failure:    "avoid using bare returns, please add return expressions",
+	})
+
+	return w
+}