Add ifshort linter (#1587)

.golangci.example.yml

@@ -293,6 +293,12 @@ linters-settings:
     packages-with-error-message:
       # specify an error message to output when a blacklisted package is used
       - github.com/sirupsen/logrus: "logging is allowed only by logutils.Log"
+  ifshort:
+    # Maximum length of variable declaration measured in number of lines, after which linter won't suggest using short syntax. 
+    # Has higher priority than max-decl-chars.
+    max-decl-lines: 1
+    # Maximum length of variable declaration measured in number of characters, after which linter won't suggest using short syntax.
+    max-decl-chars: 30
   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

@@ -11,6 +11,7 @@ require (
 	github.com/bombsimon/wsl/v3 v3.1.0
 	github.com/daixiang0/gci v0.2.8
 	github.com/denis-tingajkin/go-header v0.4.2
+	github.com/esimonov/ifshort v1.0.0
 	github.com/fatih/color v1.10.0
 	github.com/go-critic/go-critic v0.5.3
 	github.com/go-xmlfmt/xmlfmt v0.0.0-20191208150333-d5b6f63a941b

go.sum

@@ -59,6 +59,8 @@ github.com/denis-tingajkin/go-header v0.4.2 h1:jEeSF4sdv8/3cT/WY8AgDHUoItNSoEZ7q
 github.com/denis-tingajkin/go-header v0.4.2/go.mod h1:eLRHAVXzE5atsKAnNRDB90WHCFFnBUn4RN0nRcs1LJA=
 github.com/dgrijalva/jwt-go v3.2.0+incompatible/go.mod h1:E3ru+11k8xSBh+hMPgOLZmtrrCbhqsmaPHjLKYnJCaQ=
 github.com/dgryski/go-sip13 v0.0.0-20181026042036-e10d5fee7954/go.mod h1:vAd38F8PWV+bWy6jNmig1y/TA+kYO4g3RSRF0IAv0no=
+github.com/esimonov/ifshort v1.0.0 h1:mcOSoOMVtL4tJyyDTakunR+KFQUywLLAVesiWleGPHU=
+github.com/esimonov/ifshort v1.0.0/go.mod h1:yZqNJUrNn20K8Q9n2CrjTKYyVEmX209Hgu+M1LBpeZE=
 github.com/fatih/color v1.7.0/go.mod h1:Zm6kSWBoL9eyXnKyktHP6abPY2pDugNf5KwzbycvMj4=
 github.com/fatih/color v1.9.0/go.mod h1:eQcE1qtQxscV5RaZvpXrrb8Drkc3/DdQ+uUYCNjL+zU=
 github.com/fatih/color v1.10.0 h1:s36xzo75JdqLaaWoiEHk767eHiwo0598uUxyfiPkDsg=
@@ -579,6 +581,7 @@ golang.org/x/tools v0.0.0-20201001104356-43ebab892c4c/go.mod h1:z6u4i615ZeAfBE4X
 golang.org/x/tools v0.0.0-20201002184944-ecd9fd270d5d/go.mod h1:z6u4i615ZeAfBE4XtMziQW1fSVJXACjjbWkB/mvPzlU=
 golang.org/x/tools v0.0.0-20201007032633-0806396f153e/go.mod h1:z6u4i615ZeAfBE4XtMziQW1fSVJXACjjbWkB/mvPzlU=
 golang.org/x/tools v0.0.0-20201011145850-ed2f50202694/go.mod h1:z6u4i615ZeAfBE4XtMziQW1fSVJXACjjbWkB/mvPzlU=
+golang.org/x/tools v0.0.0-20201028025901-8cd080b735b3/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.0.0-20201030010431-2feb2bb1ff51/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.0.0-20201114224030-61ea331ec02b/go.mod h1:emZCQorbCU4vsT4fOWvOPXz4eW1wZW4PmDk9uLelYpA=
 golang.org/x/tools v0.0.0-20201118003311-bd56c0adb394 h1:O3VD5Fds21mB1WVRTbkiz/HTXESx6Jql5ucPZi69oiM=

pkg/config/config.go

@@ -270,6 +270,7 @@ type LintersSettings struct {
 	Makezero    MakezeroSettings
 	Thelper     ThelperSettings
 	Forbidigo   ForbidigoSettings
+	Ifshort     IfshortSettings
 	Predeclared PredeclaredSettings
 
 	Custom map[string]CustomLinterSettings
@@ -408,6 +409,11 @@ type ThelperSettings struct {
 	} `mapstructure:"benchmark"`
 }
 
+type IfshortSettings struct {
+	MaxDeclLines int `mapstructure:"max-decl-lines"`
+	MaxDeclChars int `mapstructure:"max-decl-chars"`
+}
+
 type ForbidigoSettings struct {
 	Forbid []string `mapstructure:"forbid"`
 }

pkg/golinters/ifshort.go

@@ -0,0 +1,17 @@
+package golinters
+
+import (
+	"github.com/esimonov/ifshort/pkg/analyzer"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+)
+
+func NewIfshort() *goanalysis.Linter {
+	return goanalysis.NewLinter(
+		"ifshort",
+		"Checks that your code uses short syntax for if-statements whenever possible",
+		[]*analysis.Analyzer{analyzer.Analyzer},
+		nil,
+	).WithLoadMode(goanalysis.LoadModeSyntax)
+}

pkg/lint/lintersdb/manager.go

@@ -344,6 +344,9 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 		linter.NewConfig(golinters.NewForbidigo()).
 			WithPresets(linter.PresetStyle).
 			WithURL("https://github.com/ashanbrown/forbidigo"),
+		linter.NewConfig(golinters.NewIfshort()).
+			WithPresets(linter.PresetStyle).
+			WithURL("https://github.com/esimonov/ifshort"),
 		linter.NewConfig(golinters.NewPredeclared(predeclaredCfg)).
 			WithPresets(linter.PresetStyle).
 			WithURL("https://github.com/nishanths/predeclared"),

test/testdata/ifshort.go

@@ -0,0 +1,11 @@
+//args: -Eifshort
+package testdata
+
+func DontUseShortSyntaxWhenPossible() {
+	getValue := func() interface{} { return nil }
+
+	v := getValue() // ERROR "variable 'v' is only used in the if-statement .*"
+	if v != nil {
+		return
+	}
+}