new-linter: ireturn (checks for function return type) (#2219)

.golangci.example.yml

@@ -447,6 +447,29 @@ linters-settings:
       - pkg: knative.dev/serving/pkg/apis/(\w+)/(v[\w\d]+)
         alias: $1$2
 
+  ireturn:
+    # ireturn allows using `allow` and `reject` settings at the same time.
+    # Both settings are lists of the keywords and regular expressions matched to interface or package names.
+    # keywords:
+    # - `empty` for `interface{}`
+    # - `error` for errors
+    # - `stdlib` for standard library
+    # - `anon` for anonymous interfaces
+
+    # By default, it allows using errors, empty interfaces, anonymous interfaces,
+    # and interfaces provided by the standard library.
+    allow:
+    - anon
+    - error
+    - empty
+    - stdlib
+    # You can specify idiomatic endings for interface
+    - (or|er)$
+
+    # Reject patterns
+    reject:
+    - github.com\/user\/package\/v4\.Type
+
   lll:
     # max line length, lines longer will be reported. Default is 120.
     # '\t' is counted as 1 character by default, and can be changed with the tab-width option

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/ashanbrown/makezero v0.0.0-20210520155254-b6261585ddde
 	github.com/bkielbasa/cyclop v1.2.0
 	github.com/bombsimon/wsl/v3 v3.3.0
+	github.com/butuzov/ireturn v0.1.0
 	github.com/charithe/durationcheck v0.0.8
 	github.com/daixiang0/gci v0.2.9
 	github.com/denis-tingajkin/go-header v0.4.2

pkg/config/linters_settings.go

@@ -110,6 +110,7 @@ type LintersSettings struct {
 	Gosimple         StaticCheckSettings
 	Govet            GovetSettings
 	Ifshort          IfshortSettings
+	Ireturn          IreturnSettings
 	ImportAs         ImportAsSettings
 	Lll              LllSettings
 	Makezero         MakezeroSettings
@@ -186,6 +187,11 @@ type ExhaustiveStructSettings struct {
 	StructPatterns []string `mapstructure:"struct-patterns"`
 }
 
+type IreturnSettings struct {
+	Allow  []string `mapstructure:"allow"`
+	Reject []string `mapstructure:"reject"`
+}
+
 type ForbidigoSettings struct {
 	Forbid               []string `mapstructure:"forbid"`
 	ExcludeGodocExamples bool     `mapstructure:"exclude-godoc-examples"`

pkg/golinters/ireturn.go

@@ -0,0 +1,30 @@
+package golinters
+
+import (
+	"strings"
+
+	"github.com/golangci/golangci-lint/pkg/config"
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+
+	"github.com/butuzov/ireturn/analyzer"
+	"golang.org/x/tools/go/analysis"
+)
+
+func NewIreturn(settings *config.IreturnSettings) *goanalysis.Linter {
+	a := analyzer.NewAnalyzer()
+
+	cfg := map[string]map[string]interface{}{}
+	if settings != nil {
+		cfg[a.Name] = map[string]interface{}{
+			"allow":  strings.Join(settings.Allow, ","),
+			"reject": strings.Join(settings.Reject, ","),
+		}
+	}
+
+	return goanalysis.NewLinter(
+		a.Name,
+		a.Doc,
+		[]*analysis.Analyzer{a},
+		cfg,
+	).WithLoadMode(goanalysis.LoadModeTypesInfo)
+}

pkg/lint/lintersdb/manager.go

@@ -110,6 +110,7 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 	var reviveCfg *config.ReviveSettings
 	var cyclopCfg *config.Cyclop
 	var importAsCfg *config.ImportAsSettings
+	var ireturnCfg *config.IreturnSettings
 	var goModDirectivesCfg *config.GoModDirectivesSettings
 	var tagliatelleCfg *config.TagliatelleSettings
 	var gosecCfg *config.GoSecSettings
@@ -131,6 +132,7 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 		reviveCfg = &m.cfg.LintersSettings.Revive
 		cyclopCfg = &m.cfg.LintersSettings.Cyclop
 		importAsCfg = &m.cfg.LintersSettings.ImportAs
+		ireturnCfg = &m.cfg.LintersSettings.Ireturn
 		goModDirectivesCfg = &m.cfg.LintersSettings.GoModDirectives
 		tagliatelleCfg = &m.cfg.LintersSettings.Tagliatelle
 		gosecCfg = &m.cfg.LintersSettings.Gosec
@@ -506,6 +508,11 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 			WithLoadForGoAnalysis().
 			WithURL("https://github.com/Antonboom/errname").
 			WithSince("v1.42.0"),
+		linter.NewConfig(golinters.NewIreturn(ireturnCfg)).
+			WithSince("v1.43.0").
+			WithPresets(linter.PresetStyle).
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/butuzov/ireturn"),
 
 		// nolintlint must be last because it looks at the results of all the previous linters for unused nolint directives
 		linter.NewConfig(golinters.NewNoLintLint()).

test/testdata/configs/ireturn.yml

@@ -0,0 +1,4 @@
+linters-settings:
+  ireturn:
+    allow:
+    - IreturnAllowDoer

test/testdata/configs/ireturn_stdlib_reject.yml

@@ -0,0 +1,4 @@
+linters-settings:
+  ireturn:
+    reject:
+    - stdlib

test/testdata/ireturn_allow.go

@@ -0,0 +1,13 @@
+// args: -Eireturn
+// config_path: testdata/configs/ireturn.yml
+package testdata
+
+type (
+	IreturnAllowDoer interface{ Do() }
+	ireturnAllowDoer struct{}
+)
+
+func NewAllowDoer() IreturnAllowDoer { return new(ireturnAllowDoer) }
+func (d *ireturnAllowDoer) Do()      { /*...*/ }
+
+func NewerAllowDoer() *ireturnAllowDoer { return new(ireturnAllowDoer) }

test/testdata/ireturn_default.go

@@ -0,0 +1,12 @@
+// args: -Eireturn
+package testdata
+
+type (
+	IreturnDoer interface{ Do() }
+	ireturnDoer struct{}
+)
+
+func New() IreturnDoer     { return new(ireturnDoer) } // ERROR `New returns interface \(command-line-arguments.IreturnDoer\)`
+func (d *ireturnDoer) Do() { /*...*/ }
+
+func Newer() *ireturnDoer { return new(ireturnDoer) }

test/testdata/ireturn_reject_stdlib.go

@@ -0,0 +1,28 @@
+// args: -Eireturn
+// config_path: testdata/configs/ireturn_stdlib_reject.yml
+package testdata
+
+import (
+	"bytes"
+	"io"
+)
+
+func NewWriter() io.Writer { // ERROR `NewWriter returns interface \(io.Writer\)`
+	var buf bytes.Buffer
+	return &buf
+}
+
+func TestError() error {
+	return nil
+}
+
+type Foo interface {
+	Foo()
+}
+type foo int
+
+func (f foo) Foo() {}
+
+func NewFoo() Foo {
+	return foo(1)
+}