From 745bcf65aa5b601714a58cd6ea0f63307884a031 Mon Sep 17 00:00:00 2001
From: SalvadorC <salvadorcavadini+github@gmail.com>
Date: Wed, 17 Apr 2019 22:55:52 +0200
Subject: [PATCH] bare-return (first working version) (#117)

New rule bare-return
---
 README.md                |  1 +
 RULES_DESCRIPTIONS.md    |  7 ++++
 config.go                |  1 +
 fixtures/bare-return.go  | 33 +++++++++++++++++
 rule/bare-return.go      | 77 ++++++++++++++++++++++++++++++++++++++++
 test/bare-return_test.go | 11 ++++++
 6 files changed, 130 insertions(+)
 create mode 100644 fixtures/bare-return.go
 create mode 100644 rule/bare-return.go
 create mode 100644 test/bare-return_test.go

diff --git a/README.md b/README.md
index f0fb2da..23af769 100644
--- a/README.md
+++ b/README.md
@@ -295,6 +295,7 @@ List of all available rules. The rules ported from `golint` are left unchanged a
 | [`call-to-gc`](./RULES_DESCRIPTIONS.md#call-to-gc)   | n/a    | Warns on explicit call to the garbage collector    |    no    |  no   |
 | [`duplicated-imports`](./RULES_DESCRIPTIONS#duplicated-imports) | n/a  | Looks for packages that are imported two or more times   |    no    |  no   |
 | [`import-shadowing`](./RULES_DESCRIPTIONS.md#import-shadowing)   | n/a    | Spots identifiers that shadow an import    |    no    |  no   |
+| [`bare-return`](./RULES_DESCRIPTIONS#bare-return) | n/a  | Warns on bare returns   |    no    |  no   |
 
 ## Configurable rules
 
diff --git a/RULES_DESCRIPTIONS.md b/RULES_DESCRIPTIONS.md
index 0e9a586..5e05556 100644
--- a/RULES_DESCRIPTIONS.md
+++ b/RULES_DESCRIPTIONS.md
@@ -7,6 +7,7 @@ List of all available rules.
   - [add-constant](#add-constant)
   - [argument-limit](#argument-limit)
   - [atomic](#atomic)
+  - [bare-return](#bare-return)
   - [blank-imports](#blank-imports)
   - [bool-literal-in-expr](#bool-literal-in-expr)
   - [call-to-gc](#call-to-gc)
@@ -93,6 +94,12 @@ _Description_: Check for commonly mistaken usages of the `sync/atomic` package
 
 _Configuration_: N/A
 
+## bare-return
+
+_Description_: Warns on bare (a.k.a. naked) returns
+
+_Configuration_: N/A
+
 ## blank-imports
 
 _Description_: Blank import should be only in a main or test package, or have a comment justifying it.
diff --git a/config.go b/config.go
index b1f5855..a342189 100644
--- a/config.go
+++ b/config.go
@@ -75,6 +75,7 @@ var allRules = append([]lint.Rule{
 	&rule.CallToGCRule{},
 	&rule.DuplicatedImportsRule{},
 	&rule.ImportShadowingRule{},
+	&rule.BareReturnRule{},
 }, defaultRules...)
 
 var allFormatters = []lint.Formatter{
diff --git a/fixtures/bare-return.go b/fixtures/bare-return.go
new file mode 100644
index 0000000..d2d3f8e
--- /dev/null
+++ b/fixtures/bare-return.go
@@ -0,0 +1,33 @@
+package fixtures
+
+func bare1() (int, int, error) {
+	go func() (a int) {
+		return // MATCH /avoid using bare returns, please add return expressions/
+	}(5)
+}
+
+func bare2(a, b int) (int, error, int) {
+	defer func() (a int) {
+		return // MATCH /avoid using bare returns, please add return expressions/
+	}(5)
+}
+
+func bare3(a string, b int) (a int, b float32, c string, d string) {
+	go func() (a int, b int) {
+		return a, b
+	}(5, 6)
+
+	defer func() (a int) {
+		return a
+	}(5)
+
+	return // MATCH /avoid using bare returns, please add return expressions/
+}
+
+func bare4(a string, b int) string {
+	return a
+}
+
+func bare5(a string, b int) {
+	return
+}
diff --git a/rule/bare-return.go b/rule/bare-return.go
new file mode 100644
index 0000000..dbfad2f
--- /dev/null
+++ b/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
+}
diff --git a/test/bare-return_test.go b/test/bare-return_test.go
new file mode 100644
index 0000000..1741334
--- /dev/null
+++ b/test/bare-return_test.go
@@ -0,0 +1,11 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/rule"
+)
+
+func TestBareReturn(t *testing.T) {
+	testRule(t, "bare-return", &rule.BareReturnRule{})
+}