c3

Cleanup Context Checker

c3 is a tool to analyze and warn against calling (*testing.common).Context within (*testing.common).Cleanup functions in Go tests.

(*testing.common).Context is canceled before (*testing.common).Cleanup functions are called, so calling (*testing.common).Context within (*testing.common).Cleanup functions can cause unexpected behavior.

Context returns a context that is canceled just before Cleanup-registered functions are called.¹

package a

import (
	"context"
	"testing"
)

func cleanup(t *testing.T) {
	t.Context()
}

func f(ctx context.Context) { }

func TestA(t *testing.T) {
	t.Cleanup(func() { t.Context() })          // want `avoid calling \(\*testing\.common\)\.Context inside Cleanup`
	t.Cleanup(func() { cleanup(t) })           // want `avoid calling \(\*testing\.common\)\.Context inside Cleanup`
	t.Cleanup(func() { f(t.Context()) })       // want `avoid calling \(\*testing\.common\)\.Context inside Cleanup`
	t.Cleanup(func() { context.Background() }) // ok
}

Usage

go vet

go install github.com/ikura-hamu/c3@latest

go vet -vettool=$(which c3) ./...

golangci-lint Module Plugin

https://golangci-lint.run/plugins/module-plugins/

1. Configure golangci-lint customization.

.custom-gcl.yml

version: "v1.64.1" # golangci-lint version
destination: "."
name: "custom-gcl"
plugins:
  - module: "github.com/ikura-hamu/c3"
    path: "github.com/ikura-hamu/c3"
    version: "latest"

2. Build custom golangci-lint bianry.

golangci-lint custom

3. Set up golangci-lint configuration.

.golangci.yml

linters:
  enable:
    - c3

linters-settings:
  custom:
    c3:
      type: "module"

4. Run custom golangci-lint.

./custom-gcl run

Footnotes

1. https://pkg.go.dev/testing#T.Context ↩