feat: add redundant-build-tag rule (#1135)

README.md

@@ -550,6 +550,7 @@ List of all available rules. The rules ported from `golint` are left unchanged a
 | [`comments-density`](./RULES_DESCRIPTIONS.md#comments-density) |  int (defaults to 0)  | Enforces a minimum comment / code relation |    no    |  no   |
 | [`file-length-limit`](./RULES_DESCRIPTIONS.md#file-length-limit) | map (optional)| Enforces a maximum number of lines per file |    no    |  no   |
 | [`filename-format`](./RULES_DESCRIPTIONS.md#filename-format) | regular expression (optional) | Enforces the formatting of filenames |   no    |  no   |
+| [`redundant-build-tag`](./RULES_DESCRIPTIONS.md#redundant-build-tag) | n/a   | Warns about redundant `// +build` comment lines |   no    |  no   |
 
 ## Configurable rules
 

RULES_DESCRIPTIONS.md

@@ -65,6 +65,7 @@ List of all available rules.
   - [receiver-naming](#receiver-naming)
   - [redefines-builtin-id](#redefines-builtin-id)
   - [redundant-import-alias](#redundant-import-alias)
+  - [redundant-build-tag](#redundant-build-tag)
   - [string-format](#string-format)
   - [string-of-int](#string-of-int)
   - [struct-tag](#struct-tag)
@@ -799,6 +800,13 @@ _Description_: This rule warns on redundant import aliases. This happens when th
 
 _Configuration_: N/A
 
+## redundant-build-tag
+
+_Description_: This rule warns about redundant build tag comments `// +build` when `//go:build` is present.
+`gofmt` in Go 1.17+ automatically adds the `//go:build` constraint, making the `// +build` comment unnecessary.
+
+_Configuration_: N/A
+
 ## string-format
 
 _Description_: This rule allows you to configure a list of regular expressions that string literals in certain function calls are checked against.

config/config.go

@@ -98,6 +98,7 @@ var allRules = append([]lint.Rule{
 	&rule.CommentsDensityRule{},
 	&rule.FileLengthLimitRule{},
 	&rule.FilenameFormatRule{},
+	&rule.RedundantBuildTagRule{},
 }, defaultRules...)
 
 var allFormatters = []lint.Formatter{

rule/redundant_build_tag.go

@@ -0,0 +1,43 @@
+package rule
+
+import (
+	"strings"
+
+	"github.com/mgechev/revive/lint"
+)
+
+// RedundantBuildTagRule lints the presence of redundant build tags.
+type RedundantBuildTagRule struct{}
+
+// Apply triggers if an old build tag `// +build` is found after a new one `//go:build`.
+// `//go:build` comments are automatically added by gofmt when Go 1.17+ is used.
+// See https://pkg.go.dev/cmd/go#hdr-Build_constraints
+func (*RedundantBuildTagRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
+	var failures []lint.Failure
+
+	for _, group := range file.AST.Comments {
+		hasGoBuild := false
+		for _, comment := range group.List {
+			if strings.HasPrefix(comment.Text, "//go:build ") {
+				hasGoBuild = true
+				continue
+			}
+			if hasGoBuild && strings.HasPrefix(comment.Text, "// +build ") {
+				failures = append(failures, lint.Failure{
+					Category:   "style",
+					Confidence: 1,
+					Node:       comment,
+					Failure:    `The build tag "// +build" is redundant since Go 1.17 and can be removed`,
+				})
+				return failures
+			}
+		}
+	}
+
+	return failures
+}
+
+// Name returns the rule name.
+func (*RedundantBuildTagRule) Name() string {
+	return "redundant-build-tag"
+}

test/redundant_build_tag_test.go

@@ -0,0 +1,20 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestRedundantBuildTagRule(t *testing.T) {
+	testRule(t, "redundant_build_tag", &rule.RedundantBuildTagRule{}, &lint.RuleConfig{})
+}
+
+func TestRedundantBuildTagRuleNoFailure(t *testing.T) {
+	testRule(t, "redundant_build_tag_no_failure", &rule.RedundantBuildTagRule{}, &lint.RuleConfig{})
+}
+
+func TestRedundantBuildTagRuleGo116(t *testing.T) {
+	testRule(t, "redundant_build_tag_go116", &rule.RedundantBuildTagRule{}, &lint.RuleConfig{})
+}

testdata/redundant_build_tag.go

@@ -0,0 +1,6 @@
+//go:build tag
+// +build tag
+
+// MATCH:2 /The build tag "// +build" is redundant since Go 1.17 and can be removed/
+
+package pkg

testdata/redundant_build_tag_go116.go

@@ -0,0 +1,6 @@
+// +build tag
+
+// This means that the file is for Go less than 1.17 because
+// gofmt automatically adds the new build tag `//go:build` when Go 1.17+ is used.
+
+package pkg

testdata/redundant_build_tag_no_failure.go

@@ -0,0 +1,3 @@
+//go:build tag
+
+package pkg