main.go

// testdetect provides a testingDetector generator.
package main

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/tools/go/packages"
)

//nolint:lll
const testingDetector = `// Code generated by lesiw.io/testdetect. DO NOT EDIT.
package %s

type testingDetector struct{ testingDetectorEmbed }
type testingDetectorEmbed struct{}

func (t testingDetectorEmbed) Testing() bool { return false }

var _ = (testingDetector{}).testingDetectorEmbed
`

//nolint:lll
const testingDetectorTamperProtection = `

import (
	"fmt"
	"testing"
)

var testingDetectorCovHack bool

func init() { testingDetectorInit() }
func testingDetectorInit() {
	if got, want := (testingDetector{}).Testing(), testing.Testing(); testingDetectorCovHack || got != want {
		panic(fmt.Sprintf("bad testingDetector state: got %t, want %t", got, want))
	}
}`

//nolint:lll
const testingDetectorTest = `// Code generated by lesiw.io/testdetect. DO NOT EDIT.
package %s

func (t testingDetector) Testing() bool { return true }

var _ = (testingDetector{}).testingDetectorEmbed.Testing()
`

var testingDetectorTamperProtectionTest = `func init() {
	testingDetectorCovHack = true
	defer func() { recover() }()
	testingDetectorInit()
}
`

func main() {
	if err := run(); err != nil {
		fmt.Fprintln(os.Stderr, err)
		os.Exit(1)
	}
}

func run() error {
	pkg, err := pkgname(".")
	if err != nil {
		return err
	}
	ins := pkg
	if pkg == "main" {
		ins += testingDetectorTamperProtection
	}
	err = os.WriteFile(
		"testing_detector.go",
		[]byte(fmt.Sprintf(testingDetector, ins)), 0644,
	)
	if err != nil {
		return fmt.Errorf("could not write testing_detector.go: %w", err)
	}
	data := []byte(fmt.Sprintf(testingDetectorTest, pkg))
	if pkg == "main" {
		data = append(data, []byte(testingDetectorTamperProtectionTest)...)
	}
	err = os.WriteFile("testing_detector_test.go", data, 0644)
	if err != nil {
		return fmt.Errorf("could not write testing_detector_test.go: %w", err)
	}
	return nil
}

func pkgname(path string) (string, error) {
	pkgs, err := packages.Load(&packages.Config{Mode: packages.NeedName}, ".")
	if err != nil {
		return "", fmt.Errorf("could not load package in %q: %w", path, err)
	}
	if len(pkgs) < 1 {
		return "", fmt.Errorf("could not find packages in %q", path)
	}
	var pkgErrs []error
	for _, pkg := range pkgs {
		if len(pkg.Errors) > 0 {
			for _, err := range pkg.Errors {
				pkgErrs = append(pkgErrs, err)
			}
			continue
		}
		return pkg.Name, nil
	}
	return "", errors.Join(
		append(
			[]error{fmt.Errorf("could not load package in %q", path)},
			pkgErrs...,
		)...,
	)
}