Add 'floatcompare' linter

Author: mweb

.golangci.example.yml

@@ -285,6 +285,11 @@ linters-settings:
       - '*.Test'
       - 'example.com/package.ExampleStruct'
 
+  floatcompare:
+    # Search only for == and != no other comparisons
+    # Default: false
+    equal-only: true
+
   forbidigo:
     # Forbid the following identifiers (list of regexp).
     forbid:
@@ -1726,6 +1731,7 @@ linters:
     - exhaustive
     - exhaustivestruct
     - exportloopref
+    - floatcompare
     - forbidigo
     - forcetypeassert
     - funlen

go.mod

@@ -61,6 +61,7 @@ require (
 	github.com/mitchellh/go-homedir v1.1.0
 	github.com/mitchellh/go-ps v1.0.0
 	github.com/moricho/tparallel v0.2.1
+	github.com/mweb/floatcompare v1.0.3
 	github.com/nakabonne/nestif v0.3.1
 	github.com/nishanths/exhaustive v0.7.11
 	github.com/nishanths/predeclared v0.2.1
@@ -162,7 +163,7 @@ require (
 	golang.org/x/exp/typeparams v0.0.0-20220218215828-6cf2b201936e // indirect
 	golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 // indirect
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c // indirect
-	golang.org/x/sys v0.0.0-20220319134239-a9b59b0215f8 // indirect
+	golang.org/x/sys v0.0.0-20220405052023-b1e9470b6e64 // indirect
 	golang.org/x/text v0.3.7 // indirect
 	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
 	google.golang.org/protobuf v1.27.1 // indirect

go.sum

@@ -123,6 +123,7 @@ type LintersSettings struct {
 	ErrorLint        ErrorLintSettings
 	Exhaustive       ExhaustiveSettings
 	ExhaustiveStruct ExhaustiveStructSettings
+	FloatCompare     FloatCompareSettings
 	Forbidigo        ForbidigoSettings
 	Funlen           FunlenSettings
 	Gci              GciSettings
@@ -255,6 +256,10 @@ type ExhaustiveStructSettings struct {
 	StructPatterns []string `mapstructure:"struct-patterns"`
 }
 
+type FloatCompareSettings struct {
+	EqualOnly bool `mapstructure:"equal-only"`
+}
+
 type ForbidigoSettings struct {
 	Forbid               []string `mapstructure:"forbid"`
 	ExcludeGodocExamples bool     `mapstructure:"exclude-godoc-examples"`

pkg/config/linters_settings.go

@@ -0,0 +1,29 @@
+package golinters
+
+import (
+	"github.com/mweb/floatcompare"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/config"
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+)
+
+func NewFloatCompare(settings *config.FloatCompareSettings) *goanalysis.Linter {
+	a := floatcompare.NewAnalyzer()
+
+	var cfg map[string]map[string]interface{}
+	if settings != nil {
+		d := map[string]interface{}{
+			"equalOnly": settings.EqualOnly,
+		}
+
+		cfg = map[string]map[string]interface{}{a.Name: d}
+	}
+
+	return goanalysis.NewLinter(
+		a.Name,
+		a.Doc,
+		[]*analysis.Analyzer{a},
+		cfg,
+	).WithLoadMode(goanalysis.LoadModeTypesInfo)
+}

pkg/golinters/floatcompare.go

@@ -107,6 +107,7 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 	var errorlintCfg *config.ErrorLintSettings
 	var exhaustiveCfg *config.ExhaustiveSettings
 	var exhaustiveStructCfg *config.ExhaustiveStructSettings
+	var floatCompareStructCfg *config.FloatCompareSettings
 	var gciCfg *config.GciSettings
 	var goModDirectivesCfg *config.GoModDirectivesSettings
 	var goMndCfg *config.GoMndSettings
@@ -140,6 +141,7 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 		errorlintCfg = &m.cfg.LintersSettings.ErrorLint
 		exhaustiveCfg = &m.cfg.LintersSettings.Exhaustive
 		exhaustiveStructCfg = &m.cfg.LintersSettings.ExhaustiveStruct
+		floatCompareStructCfg = &m.cfg.LintersSettings.FloatCompare
 		gciCfg = &m.cfg.LintersSettings.Gci
 		goModDirectivesCfg = &m.cfg.LintersSettings.GoModDirectives
 		goMndCfg = &m.cfg.LintersSettings.Gomnd
@@ -289,6 +291,12 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 			WithLoadForGoAnalysis().
 			WithURL("https://github.com/kyoh86/exportloopref"),
 
+		linter.NewConfig(golinters.NewFloatCompare(floatCompareStructCfg)).
+			WithSince("v1.46.0").
+			WithPresets(linter.PresetBugs).
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/mweb/floatcompare"),
+
 		linter.NewConfig(golinters.NewForbidigo()).
 			WithSince("v1.34.0").
 			WithPresets(linter.PresetStyle).

pkg/lint/lintersdb/manager.go

@@ -0,0 +1,71 @@
+// args: -Efloatcompare
+package testdata
+
+import "fmt"
+
+func EqualCompareIfFloats() {
+	x, y := 400., 500.
+	if 300. == 100. { // ERROR `float comparison found "300. == 100."`
+		dummy()
+	}
+	if x == y { // ERROR `float comparison found "x == y"`
+		dummy()
+	}
+	if 300.+200. == 10. { // ERROR `float comparison found "300.+200. == 10."`
+		dummy()
+	}
+	if 300 == 200 {
+		dummy()
+	}
+}
+
+func NotEqualCompareIfFloats() {
+	x, y := 400., 500.
+	if 300. != 100. { // ERROR `float comparison found "300. != 100."`
+
+		dummy()
+	}
+	if x != y { // ERROR `float comparison found "x != y"`
+		dummy()
+	}
+}
+
+func EqualCompareIfCustomType() {
+	type number float64
+	var x, y number = 300., 400.
+	if x == y { // ERROR `float comparison found "x == y"`
+		dummy()
+	}
+}
+
+func GreaterLessCompareIfFloats() {
+	if 300. >= 100. { // ERROR `float comparison found "300. >= 100."`
+		dummy()
+	}
+	if 300. <= 100. { // ERROR `float comparison found "300. <= 100."`
+		dummy()
+	}
+	if 300. < 100. { // ERROR `float comparison found "300. < 100."`
+		dummy()
+	}
+	if 300. > 100. { // ERROR `float comparison found "300. > 100."`
+		dummy()
+	}
+}
+
+func SwitchStmtWithFloat() {
+	switch 300. { // ERROR "float comparison with switch statement"
+	case 100.:
+	case 200:
+	}
+}
+
+func EqualCompareSwitchFloats() {
+	switch {
+	case 100. == 200.: // ERROR `float comparison found "100. == 200."`
+	}
+}
+
+func dummy() {
+	fmt.Println("dummy()")
+}