Fix #98: nakedret linter support

Author: jirfag

Diff for: .golangci.example.yml

@@ -125,6 +125,9 @@ linters-settings:
     # if it's called for subdir of a project it can't find external interfaces. All text editor integrations
     # with golangci-lint call it on a directory with the changed file.
     check-exported: false
+  nakedret:
+    # make an issue if func has more lines of code than this setting and it has naked returns; default is 30
+    max-func-lines: 30
 
 
 linters:

Diff for: README.md

@@ -123,6 +123,7 @@ depguard: Go linter that checks if package imports are in a list of acceptable p
 misspell: Finds commonly misspelled English words in comments [fast: true]
 lll: Reports long lines [fast: true]
 unparam: Reports unused function parameters [fast: false]
+nakedret: Finds naked returns in functions greater than a specified function length [fast: true]
 ```
 
 Pass `-E/--enable` to enable linter and `-D/--disable` to disable:
@@ -231,6 +232,7 @@ golangci-lint linters
 - [misspell](https://github.com/client9/misspell) - Finds commonly misspelled English words in comments
 - [lll](https://github.com/walle/lll) - Reports long lines
 - [unparam](https://github.com/mvdan/unparam) - Reports unused function parameters
+- [nakedret](https://github.com/alexkohler/nakedret) - Finds naked returns in functions greater than a specified function length
 
 # Configuration
 The config file has lower priority than command-line options. If the same bool/string/int option is provided on the command-line
@@ -454,6 +456,9 @@ linters-settings:
     # if it's called for subdir of a project it can't find external interfaces. All text editor integrations
     # with golangci-lint call it on a directory with the changed file.
     check-exported: false
+  nakedret:
+    # make an issue if func has more lines of code than this setting and it has naked returns; default is 30
+    max-func-lines: 30
 
 
 linters:
@@ -636,6 +641,7 @@ Thanks to developers and authors of used linters:
 - [OpenPeeDeeP](https://github.com/OpenPeeDeeP)
 - [client9](https://github.com/client9)
 - [walle](https://github.com/walle)
+- [alexkohler](https://github.com/alexkohler)
 
 # Future Plans
 1. Upstream all changes of forked linters.

Diff for: pkg/config/config.go

@@ -160,26 +160,34 @@ type LintersSettings struct {
 		CheckExported bool `mapstructure:"check-exported"`
 	}
 
-	Lll     LllSettings
-	Unparam UnparamSettings
+	Lll      LllSettings
+	Unparam  UnparamSettings
+	Nakedret NakedretSettings
 }
 
 type LllSettings struct {
 	LineLength int `mapstructure:"line-length"`
 }
 
+type NakedretSettings struct {
+	MaxFuncLines int `mapstructure:"max-func-lines"`
+}
+
+type UnparamSettings struct {
+	CheckExported bool `mapstructure:"check-exported"`
+	Algo          string
+}
+
 var defaultLintersSettings = LintersSettings{
 	Lll: LllSettings{
 		LineLength: 120,
 	},
 	Unparam: UnparamSettings{
 		Algo: "cha",
 	},
-}
-
-type UnparamSettings struct {
-	CheckExported bool `mapstructure:"check-exported"`
-	Algo          string
+	Nakedret: NakedretSettings{
+		MaxFuncLines: 30,
+	},
 }
 
 type Linters struct {

Diff for: pkg/golinters/nakedret.go

@@ -0,0 +1,100 @@
+package golinters
+
+import (
+	"context"
+	"fmt"
+	"go/ast"
+	"go/token"
+
+	"github.com/golangci/golangci-lint/pkg/lint/linter"
+	"github.com/golangci/golangci-lint/pkg/result"
+)
+
+type Nakedret struct{}
+
+func (Nakedret) Name() string {
+	return "nakedret"
+}
+
+func (Nakedret) Desc() string {
+	return "Finds naked returns in functions greater than a specified function length"
+}
+
+type nakedretVisitor struct {
+	maxLength int
+	f         *token.FileSet
+	issues    []result.Issue
+}
+
+func (v *nakedretVisitor) processFuncDecl(funcDecl *ast.FuncDecl) {
+	file := v.f.File(funcDecl.Pos())
+	functionLineLength := file.Position(funcDecl.End()).Line - file.Position(funcDecl.Pos()).Line
+
+	// Scan the body for usage of the named returns
+	for _, stmt := range funcDecl.Body.List {
+		s, ok := stmt.(*ast.ReturnStmt)
+		if !ok {
+			continue
+		}
+
+		if len(s.Results) != 0 {
+			continue
+		}
+
+		file := v.f.File(s.Pos())
+		if file == nil || functionLineLength <= v.maxLength {
+			continue
+		}
+		if funcDecl.Name == nil {
+			continue
+		}
+
+		v.issues = append(v.issues, result.Issue{
+			FromLinter: Nakedret{}.Name(),
+			Text: fmt.Sprintf("naked return in func `%s` with %d lines of code",
+				funcDecl.Name.Name, functionLineLength),
+			Pos: v.f.Position(s.Pos()),
+		})
+	}
+}
+
+func (v *nakedretVisitor) Visit(node ast.Node) ast.Visitor {
+	funcDecl, ok := node.(*ast.FuncDecl)
+	if !ok {
+		return v
+	}
+
+	var namedReturns []*ast.Ident
+
+	// We've found a function
+	if funcDecl.Type != nil && funcDecl.Type.Results != nil {
+		for _, field := range funcDecl.Type.Results.List {
+			for _, ident := range field.Names {
+				if ident != nil {
+					namedReturns = append(namedReturns, ident)
+				}
+			}
+		}
+	}
+
+	if len(namedReturns) == 0 || funcDecl.Body == nil {
+		return v
+	}
+
+	v.processFuncDecl(funcDecl)
+	return v
+}
+
+func (lint Nakedret) Run(ctx context.Context, lintCtx *linter.Context) ([]result.Issue, error) {
+	var res []result.Issue
+	for _, f := range lintCtx.ASTCache.GetAllValidFiles() {
+		v := nakedretVisitor{
+			maxLength: lintCtx.Settings().Nakedret.MaxFuncLines,
+			f:         f.Fset,
+		}
+		ast.Walk(&v, f.F)
+		res = append(res, v.issues...)
+	}
+
+	return res, nil
+}

Diff for: pkg/lint/lintersdb/lintersdb.go

@@ -177,6 +177,10 @@ func GetAllSupportedLinterConfigs() []linter.Config {
 			WithFullImport().
 			WithSSA().
 			WithURL("https://github.com/mvdan/unparam"),
+		linter.NewConfig(golinters.Nakedret{}).
+			WithPresets(linter.PresetComplexity).
+			WithSpeed(10).
+			WithURL("https://github.com/alexkohler/nakedret"),
 	}
 
 	if os.Getenv("GOLANGCI_COM_RUN") == "1" {
@@ -188,6 +192,7 @@ func GetAllSupportedLinterConfigs() []linter.Config {
 			golinters.Misspell{}.Name():  true, // unsure about false-positives number
 			golinters.Lll{}.Name():       true, // annoying
 			golinters.Unparam{}.Name():   true, // need to check it first
+			golinters.Nakedret{}.Name():  true, // annoying
 		}
 		return enableLinterConfigs(lcs, func(lc *linter.Config) bool {
 			return !disabled[lc.Linter.Name()]

Diff for: test/testdata/nakedret.go

@@ -0,0 +1,67 @@
+//args: -Enakedret
+package testdata
+
+func NakedretIssue() (a int, b string) {
+	if a > 0 {
+		return
+	}
+
+	if b == "" {
+		return 0, "0"
+	}
+
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+
+	// len of this function is 31
+	return // ERROR "naked return in func `NakedretIssue` with 31 lines of code"
+}
+
+func NoNakedretIssue() (a int, b string) {
+	if a > 0 {
+		return
+	}
+
+	if b == "" {
+		return 0, "0"
+	}
+
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+	// ...
+
+	// len of this function is 30
+	return
+}

Diff for: third_party/nakedret/LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2017 Alex Kohler
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.