From 7b5689f42873d3a13921b2c008359c599451ceac Mon Sep 17 00:00:00 2001
From: Quang-Minh Nguyen <qmnguyen@gitlab.com>
Date: Wed, 21 Jun 2023 15:30:21 +0700
Subject: Implement a linter to discourage future usage of Unavailable code

The prior commit fixes inelligible usages of Unavailable status codes.
To prevent this situation from happening in the future, this commit
implements a linter that it warns occurrences where Unavailable code is
used. Engineers can ignore it by adding a comment, but at least this
practice catches their eyes.
---
 tools/golangci-lint/gitaly/lint.go                 |  4 ++
 .../src/unavailable_code/unavailable_code_test.go  | 21 ++++++++++
 tools/golangci-lint/gitaly/unavailable_code.go     | 48 ++++++++++++++++++++++
 .../golangci-lint/gitaly/unavailable_code_test.go  | 22 ++++++++++
 4 files changed, 95 insertions(+)
 create mode 100644 tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go
 create mode 100644 tools/golangci-lint/gitaly/unavailable_code.go
 create mode 100644 tools/golangci-lint/gitaly/unavailable_code_test.go

(limited to 'tools')

diff --git a/tools/golangci-lint/gitaly/lint.go b/tools/golangci-lint/gitaly/lint.go
index 1d76a9400..6840b15ac 100644
--- a/tools/golangci-lint/gitaly/lint.go
+++ b/tools/golangci-lint/gitaly/lint.go
@@ -23,6 +23,10 @@ func (p *analyzerPlugin) GetAnalyzers() []*analysis.Analyzer {
 				"included-functions",
 			),
 		}),
+		newUnavailableCodeAnalyzer(&unavailableCodeAnalyzerSettings{IncludedFunctions: p.configStringSlicesAt(
+			unavailableCodeAnalyzerName,
+			"included-functions",
+		)}),
 	}
 }
 
diff --git a/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go b/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go
new file mode 100644
index 000000000..5493e3f7a
--- /dev/null
+++ b/tools/golangci-lint/gitaly/testdata/src/unavailable_code/unavailable_code_test.go
@@ -0,0 +1,21 @@
+package unavailable_code
+
+import (
+	"fmt"
+)
+
+func NewUnavailable(msg string) error {
+	return fmt.Errorf("unavailable: %s", msg)
+}
+
+func NewAborted(msg string) error {
+	return fmt.Errorf("aborted: %s", msg)
+}
+
+func errorWrapOkay() {
+	_ = NewAborted("hello world")
+}
+
+func errorWrapNotOkay() {
+	_ = NewUnavailable("hello world") // please avoid using the Unavailable status code: https://gitlab.com/gitlab-org/gitaly/-/blob/master/STYLE.md?plain=0#unavailable-code
+}
diff --git a/tools/golangci-lint/gitaly/unavailable_code.go b/tools/golangci-lint/gitaly/unavailable_code.go
new file mode 100644
index 000000000..9546b1871
--- /dev/null
+++ b/tools/golangci-lint/gitaly/unavailable_code.go
@@ -0,0 +1,48 @@
+package main
+
+import (
+	"go/ast"
+
+	"golang.org/x/tools/go/analysis"
+)
+
+const unavailableCodeAnalyzerName = "unavailable_code"
+
+type unavailableCodeAnalyzerSettings struct {
+	IncludedFunctions []string `mapstructure:"included-functions"`
+}
+
+// newErrorWrapAnalyzer warns if Unavailable status code is used. Unavailable status code is reserved to signal server's
+// unavailability. It should be used by some specific components. gRPC handlers should typically avoid this type of
+// error.
+// For more information:
+// https://gitlab.com/gitlab-org/gitaly/-/blob/master/STYLE.md?plain=0#unavailable-code
+func newUnavailableCodeAnalyzer(settings *unavailableCodeAnalyzerSettings) *analysis.Analyzer {
+	return &analysis.Analyzer{
+		Name: unavailableCodeAnalyzerName,
+		Doc:  `discourage the usage of Unavailable status code`,
+		Run:  runUnavailableCodeAnalyzer(settings.IncludedFunctions),
+	}
+}
+
+func runUnavailableCodeAnalyzer(rules []string) func(*analysis.Pass) (interface{}, error) {
+	return func(pass *analysis.Pass) (interface{}, error) {
+		matcher := NewMatcher(pass)
+		for _, file := range pass.Files {
+			ast.Inspect(file, func(n ast.Node) bool {
+				if call, ok := n.(*ast.CallExpr); ok {
+					if matcher.MatchFunction(call, rules) {
+						pass.Report(analysis.Diagnostic{
+							Pos:            call.Pos(),
+							End:            call.End(),
+							Message:        "please avoid using the Unavailable status code: https://gitlab.com/gitlab-org/gitaly/-/blob/master/STYLE.md?plain=0#unavailable-code",
+							SuggestedFixes: nil,
+						})
+					}
+				}
+				return true
+			})
+		}
+		return nil, nil
+	}
+}
diff --git a/tools/golangci-lint/gitaly/unavailable_code_test.go b/tools/golangci-lint/gitaly/unavailable_code_test.go
new file mode 100644
index 000000000..39d97e788
--- /dev/null
+++ b/tools/golangci-lint/gitaly/unavailable_code_test.go
@@ -0,0 +1,22 @@
+package main
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+
+	"golang.org/x/tools/go/analysis/analysistest"
+)
+
+func TestUnavailableCode(t *testing.T) {
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("Failed to get wd: %s", err)
+	}
+
+	testdata := filepath.Join(wd, "testdata")
+	analyzer := newUnavailableCodeAnalyzer(&unavailableCodeAnalyzerSettings{IncludedFunctions: []string{
+		"unavailable_code.NewUnavailable",
+	}})
+	analysistest.Run(t, testdata, analyzer, "unavailable_code")
+}
-- 
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