Add ptrequality linter

ptrequality is a Go linter (static analysis tool) that detects comparisons against
the address of newly created values, such as ptr == &MyStruct{} or ptr == new(MyStruct).

https://pkg.go.dev/fillmore-labs.com/cmplint

Signed-off-by: Oliver Eikemeier <[email protected]>

Author: eikemeier

go.mod

@@ -5,6 +5,7 @@ go 1.23.0
 require (
 	4d63.com/gocheckcompilerdirectives v1.3.0
 	4d63.com/gochecknoglobals v0.2.2
+	fillmore-labs.com/cmplint v0.0.3
 	github.com/4meepo/tagalign v1.4.2
 	github.com/Abirdcfly/dupword v0.1.6
 	github.com/AlwxSin/noinlineerr v1.0.3

go.sum

@@ -804,6 +804,7 @@
             "predeclared",
             "promlinter",
             "protogetter",
+            "ptrequality",
             "reassign",
             "recvcheck",
             "revive",
@@ -2881,6 +2882,17 @@
             }
           }
         },
+        "ptrequalitySettings": {
+          "type": "object",
+          "additionalProperties": false,
+          "properties": {
+            "check-is": {
+              "description": "Suppress check for errors with \"Is\" method",
+              "type": "boolean",
+              "default": true
+            }
+          }
+        },
         "reviveSettings": {
           "type": "object",
           "additionalProperties": false,
@@ -4530,6 +4542,9 @@
             "protogetter": {
               "$ref": "#/definitions/settings/definitions/protogetterSettings"
             },
+            "ptrequality": {
+              "$ref": "#/definitions/settings/definitions/ptrequalitySettings"
+            },
             "revive": {
               "$ref": "#/definitions/settings/definitions/reviveSettings"
             },

jsonschema/golangci.next.jsonschema.json

@@ -137,6 +137,9 @@ var defaultLintersSettings = LintersSettings{
 	Predeclared: PredeclaredSettings{
 		Qualified: false,
 	},
+	PtrEquality: PtrEqualitySettings{
+		CheckIs: true,
+	},
 	SlogLint: SlogLintSettings{
 		NoMixedArgs:    true,
 		KVOnly:         false,
@@ -263,6 +266,7 @@ type LintersSettings struct {
 	Predeclared              PredeclaredSettings              `mapstructure:"predeclared"`
 	Promlinter               PromlinterSettings               `mapstructure:"promlinter"`
 	ProtoGetter              ProtoGetterSettings              `mapstructure:"protogetter"`
+	PtrEquality              PtrEqualitySettings              `mapstructure:"ptrequality"`
 	Reassign                 ReassignSettings                 `mapstructure:"reassign"`
 	Recvcheck                RecvcheckSettings                `mapstructure:"recvcheck"`
 	Revive                   ReviveSettings                   `mapstructure:"revive"`
@@ -761,6 +765,10 @@ type ProtoGetterSettings struct {
 	ReplaceFirstArgInAppend bool     `mapstructure:"replace-first-arg-in-append"`
 }
 
+type PtrEqualitySettings struct {
+	CheckIs bool `mapstructure:"check-is"`
+}
+
 type ReassignSettings struct {
 	Patterns []string `mapstructure:"patterns"`
 }

pkg/config/linters_settings.go

@@ -0,0 +1,24 @@
+package ptrequality
+
+import (
+	"fillmore-labs.com/cmplint/analyzer"
+
+	"github.com/golangci/golangci-lint/v2/pkg/config"
+	"github.com/golangci/golangci-lint/v2/pkg/goanalysis"
+)
+
+const (
+	Name = "ptrequality"
+	Doc  = "Detect new pointers used within equality comparisons, making the result always false or undefined"
+)
+
+func New(settings *config.PtrEqualitySettings) *goanalysis.Linter {
+	a := analyzer.New(
+		analyzer.WithName(Name),
+		analyzer.WithDoc(Doc),
+		analyzer.WithCheckIs(settings.CheckIs),
+	)
+
+	return goanalysis.NewLinterFromAnalyzer(a).
+		WithLoadMode(goanalysis.LoadModeTypesInfo)
+}

pkg/golinters/ptrequality/ptrequality.go

@@ -0,0 +1,11 @@
+package ptrequality
+
+import (
+	"testing"
+
+	"github.com/golangci/golangci-lint/v2/test/testshared/integration"
+)
+
+func TestFromTestdata(t *testing.T) {
+	integration.RunTestdata(t)
+}

pkg/golinters/ptrequality/ptrequality_integration_test.go

@@ -0,0 +1,22 @@
+//golangcitest:args -Eptrequality
+//golangcitest:config_path testdata/ptrequality.yml
+package main
+
+import (
+	"errors"
+	"log"
+	"net/url"
+)
+
+func main() {
+	_, err := url.Parse("://example.com")
+
+	if errors.Is(err, &url.Error{}) { // want "is always false"
+		log.Fatal("Cannot parse URL")
+	}
+
+	var urlErr *url.Error
+	if errors.As(err, &urlErr) {
+		log.Fatalf("Cannot parse URL: %v", urlErr)
+	}
+}

pkg/golinters/ptrequality/testdata/ptrequality.go

@@ -0,0 +1,6 @@
+version: "2"
+
+linters:
+  settings:
+    ptrequality:
+      check-is: false

pkg/golinters/ptrequality/testdata/ptrequality.yml

@@ -89,6 +89,7 @@ import (
 	"github.com/golangci/golangci-lint/v2/pkg/golinters/predeclared"
 	"github.com/golangci/golangci-lint/v2/pkg/golinters/promlinter"
 	"github.com/golangci/golangci-lint/v2/pkg/golinters/protogetter"
+	"github.com/golangci/golangci-lint/v2/pkg/golinters/ptrequality"
 	"github.com/golangci/golangci-lint/v2/pkg/golinters/reassign"
 	"github.com/golangci/golangci-lint/v2/pkg/golinters/recvcheck"
 	"github.com/golangci/golangci-lint/v2/pkg/golinters/revive"
@@ -555,6 +556,11 @@ func (LinterBuilder) Build(cfg *config.Config) ([]*linter.Config, error) {
 			WithAutoFix().
 			WithURL("https://github.com/ghostiam/protogetter"),
 
+		linter.NewConfig(ptrequality.New(&cfg.Linters.Settings.PtrEquality)).
+			WithSince("v2.2.0").
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/fillmore-labs/cmplint"),
+
 		linter.NewConfig(reassign.New(&cfg.Linters.Settings.Reassign)).
 			WithSince("v1.49.0").
 			WithLoadForGoAnalysis().