src/internal/testenv/exec.go - go - Git at Google

 // Copyright 2015 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.

 package testenv

 import (
 	"context"
 	"errors"
 	"fmt"
 	"os"
 	"os/exec"
 	"runtime"
 	"strconv"
 	"strings"
 	"sync"
 	"testing"
 	"time"
 )

 // MustHaveExec checks that the current system can start new processes
 // using os.StartProcess or (more commonly) exec.Command.
 // If not, MustHaveExec calls t.Skip with an explanation.
 //
 // On some platforms MustHaveExec checks for exec support by re-executing the
 // current executable, which must be a binary built by 'go test'.
 // We intentionally do not provide a HasExec function because of the risk of
 // inappropriate recursion in TestMain functions.
 //
 // To check for exec support outside of a test, just try to exec the command.
 // If exec is not supported, testenv.SyscallIsNotSupported will return true
 // for the resulting error.
 func MustHaveExec(t testing.TB) {
 	tryExecOnce.Do(func() {
 		tryExecErr = tryExec()
 	})
 	if tryExecErr != nil {
 		t.Skipf("skipping test: cannot exec subprocess on %s/%s: %v", runtime.GOOS, runtime.GOARCH, tryExecErr)
 	}
 }

 var (
 	tryExecOnce sync.Once
 	tryExecErr  error
 )

 func tryExec() error {
 	switch runtime.GOOS {
 	case "wasip1", "js", "ios":
 	default:
 		// Assume that exec always works on non-mobile platforms and Android.
 		return nil
 	}

 	// ios has an exec syscall but on real iOS devices it might return a
 	// permission error. In an emulated environment (such as a Corellium host)
 	// it might succeed, so if we need to exec we'll just have to try it and
 	// find out.
 	//
 	// As of 2023-04-19 wasip1 and js don't have exec syscalls at all, but we
 	// may as well use the same path so that this branch can be tested without
 	// an ios environment.

 	if !testing.Testing() {
 		// This isn't a standard 'go test' binary, so we don't know how to
 		// self-exec in a way that should succeed without side effects.
 		// Just forget it.
 		return errors.New("can't probe for exec support with a non-test executable")
 	}

 	// We know that this is a test executable. We should be able to run it with a
 	// no-op flag to check for overall exec support.
 	exe, err := os.Executable()
 	if err != nil {
 		return fmt.Errorf("can't probe for exec support: %w", err)
 	}
 	cmd := exec.Command(exe, "-test.list=^$")
 	cmd.Env = origEnv
 	return cmd.Run()
 }

 var execPaths sync.Map // path -> error

 // MustHaveExecPath checks that the current system can start the named executable
 // using os.StartProcess or (more commonly) exec.Command.
 // If not, MustHaveExecPath calls t.Skip with an explanation.
 func MustHaveExecPath(t testing.TB, path string) {
 	MustHaveExec(t)

 	err, found := execPaths.Load(path)
 	if !found {
 		_, err = exec.LookPath(path)
 		err, _ = execPaths.LoadOrStore(path, err)
 	}
 	if err != nil {
 		t.Skipf("skipping test: %s: %s", path, err)
 	}
 }

 // CleanCmdEnv will fill cmd.Env with the environment, excluding certain
 // variables that could modify the behavior of the Go tools such as
 // GODEBUG and GOTRACEBACK.
 func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
 	if cmd.Env != nil {
 		panic("environment already set")
 	}
 	for _, env := range os.Environ() {
 		// Exclude GODEBUG from the environment to prevent its output
 		// from breaking tests that are trying to parse other command output.
 		if strings.HasPrefix(env, "GODEBUG=") {
 			continue
 		}
 		// Exclude GOTRACEBACK for the same reason.
 		if strings.HasPrefix(env, "GOTRACEBACK=") {
 			continue
 		}
 		cmd.Env = append(cmd.Env, env)
 	}
 	return cmd
 }

 // CommandContext is like exec.CommandContext, but:
 //   - skips t if the platform does not support os/exec,
 //   - sends SIGQUIT (if supported by the platform) instead of SIGKILL
 //     in its Cancel function
 //   - if the test has a deadline, adds a Context timeout and WaitDelay
 //     for an arbitrary grace period before the test's deadline expires,
 //   - fails the test if the command does not complete before the test's deadline, and
 //   - sets a Cleanup function that verifies that the test did not leak a subprocess.
 func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
 	t.Helper()
 	MustHaveExec(t)

 	var (
 		cancelCtx   context.CancelFunc
 		gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
 	)

 	if t, ok := t.(interface {
 		testing.TB
 		Deadline() (time.Time, bool)
 	}); ok {
 		if td, ok := t.Deadline(); ok {
 			// Start with a minimum grace period, just long enough to consume the
 			// output of a reasonable program after it terminates.
 			gracePeriod = 100 * time.Millisecond
 			if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
 				scale, err := strconv.Atoi(s)
 				if err != nil {
 					t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
 				}
 				gracePeriod *= time.Duration(scale)
 			}

 			// If time allows, increase the termination grace period to 5% of the
 			// test's remaining time.
 			testTimeout := time.Until(td)
 			if gp := testTimeout / 20; gp > gracePeriod {
 				gracePeriod = gp
 			}

 			// When we run commands that execute subprocesses, we want to reserve two
 			// grace periods to clean up: one for the delay between the first
 			// termination signal being sent (via the Cancel callback when the Context
 			// expires) and the process being forcibly terminated (via the WaitDelay
 			// field), and a second one for the delay between the process being
 			// terminated and the test logging its output for debugging.
 			//
 			// (We want to ensure that the test process itself has enough time to
 			// log the output before it is also terminated.)
 			cmdTimeout := testTimeout - 2*gracePeriod

 			if cd, ok := ctx.Deadline(); !ok || time.Until(cd) > cmdTimeout {
 				// Either ctx doesn't have a deadline, or its deadline would expire
 				// after (or too close before) the test has already timed out.
 				// Add a shorter timeout so that the test will produce useful output.
 				ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
 			}
 		}
 	}

 	cmd := exec.CommandContext(ctx, name, args...)
 	cmd.Cancel = func() error {
 		if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
 			// The command timed out due to running too close to the test's deadline.
 			// There is no way the test did that intentionally — it's too close to the
 			// wire! — so mark it as a test failure. That way, if the test expects the
 			// command to fail for some other reason, it doesn't have to distinguish
 			// between that reason and a timeout.
 			t.Errorf("test timed out while running command: %v", cmd)
 		} else {
 			// The command is being terminated due to ctx being canceled, but
 			// apparently not due to an explicit test deadline that we added.
 			// Log that information in case it is useful for diagnosing a failure,
 			// but don't actually fail the test because of it.
 			t.Logf("%v: terminating command: %v", ctx.Err(), cmd)
 		}
 		return cmd.Process.Signal(Sigquit)
 	}
 	cmd.WaitDelay = gracePeriod

 	t.Cleanup(func() {
 		if cancelCtx != nil {
 			cancelCtx()
 		}
 		if cmd.Process != nil && cmd.ProcessState == nil {
 			t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)
 		}
 	})

 	return cmd
 }

 // Command is like exec.Command, but applies the same changes as
 // testenv.CommandContext (with a default Context).
 func Command(t testing.TB, name string, args ...string) *exec.Cmd {
 	t.Helper()
 	return CommandContext(t, context.Background(), name, args...)
 }
	// Copyright 2015 The Go Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style
	// license that can be found in the LICENSE file.

	package testenv

	import (
	"context"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"runtime"
	"strconv"
	"strings"
	"sync"
	"testing"
	"time"
	)

	// MustHaveExec checks that the current system can start new processes
	// using os.StartProcess or (more commonly) exec.Command.
	// If not, MustHaveExec calls t.Skip with an explanation.
	//
	// On some platforms MustHaveExec checks for exec support by re-executing the
	// current executable, which must be a binary built by 'go test'.
	// We intentionally do not provide a HasExec function because of the risk of
	// inappropriate recursion in TestMain functions.
	//
	// To check for exec support outside of a test, just try to exec the command.
	// If exec is not supported, testenv.SyscallIsNotSupported will return true
	// for the resulting error.
	func MustHaveExec(t testing.TB) {
	tryExecOnce.Do(func() {
	tryExecErr = tryExec()
	})
	if tryExecErr != nil {
	t.Skipf("skipping test: cannot exec subprocess on %s/%s: %v", runtime.GOOS, runtime.GOARCH, tryExecErr)
	}
	}

	var (
	tryExecOnce sync.Once
	tryExecErr error
	)

	func tryExec() error {
	switch runtime.GOOS {
	case "wasip1", "js", "ios":
	default:
	// Assume that exec always works on non-mobile platforms and Android.
	return nil
	}

	// ios has an exec syscall but on real iOS devices it might return a
	// permission error. In an emulated environment (such as a Corellium host)
	// it might succeed, so if we need to exec we'll just have to try it and
	// find out.
	//
	// As of 2023-04-19 wasip1 and js don't have exec syscalls at all, but we
	// may as well use the same path so that this branch can be tested without
	// an ios environment.

	if !testing.Testing() {
	// This isn't a standard 'go test' binary, so we don't know how to
	// self-exec in a way that should succeed without side effects.
	// Just forget it.
	return errors.New("can't probe for exec support with a non-test executable")
	}

	// We know that this is a test executable. We should be able to run it with a
	// no-op flag to check for overall exec support.
	exe, err := os.Executable()
	if err != nil {
	return fmt.Errorf("can't probe for exec support: %w", err)
	}
	cmd := exec.Command(exe, "-test.list=^$")
	cmd.Env = origEnv
	return cmd.Run()
	}

	var execPaths sync.Map // path -> error

	// MustHaveExecPath checks that the current system can start the named executable
	// using os.StartProcess or (more commonly) exec.Command.
	// If not, MustHaveExecPath calls t.Skip with an explanation.
	func MustHaveExecPath(t testing.TB, path string) {
	MustHaveExec(t)

	err, found := execPaths.Load(path)
	if !found {
	_, err = exec.LookPath(path)
	err, _ = execPaths.LoadOrStore(path, err)
	}
	if err != nil {
	t.Skipf("skipping test: %s: %s", path, err)
	}
	}

	// CleanCmdEnv will fill cmd.Env with the environment, excluding certain
	// variables that could modify the behavior of the Go tools such as
	// GODEBUG and GOTRACEBACK.
	func CleanCmdEnv(cmd exec.Cmd) exec.Cmd {
	if cmd.Env != nil {
	panic("environment already set")
	}
	for _, env := range os.Environ() {
	// Exclude GODEBUG from the environment to prevent its output
	// from breaking tests that are trying to parse other command output.
	if strings.HasPrefix(env, "GODEBUG=") {
	continue
	}
	// Exclude GOTRACEBACK for the same reason.
	if strings.HasPrefix(env, "GOTRACEBACK=") {
	continue
	}
	cmd.Env = append(cmd.Env, env)
	}
	return cmd
	}

	// CommandContext is like exec.CommandContext, but:
	// - skips t if the platform does not support os/exec,
	// - sends SIGQUIT (if supported by the platform) instead of SIGKILL
	// in its Cancel function
	// - if the test has a deadline, adds a Context timeout and WaitDelay
	// for an arbitrary grace period before the test's deadline expires,
	// - fails the test if the command does not complete before the test's deadline, and
	// - sets a Cleanup function that verifies that the test did not leak a subprocess.
	func CommandContext(t testing.TB, ctx context.Context, name string, args ...string) *exec.Cmd {
	t.Helper()
	MustHaveExec(t)

	var (
	cancelCtx context.CancelFunc
	gracePeriod time.Duration // unlimited unless the test has a deadline (to allow for interactive debugging)
	)

	if t, ok := t.(interface {
	testing.TB
	Deadline() (time.Time, bool)
	}); ok {
	if td, ok := t.Deadline(); ok {
	// Start with a minimum grace period, just long enough to consume the
	// output of a reasonable program after it terminates.
	gracePeriod = 100 * time.Millisecond
	if s := os.Getenv("GO_TEST_TIMEOUT_SCALE"); s != "" {
	scale, err := strconv.Atoi(s)
	if err != nil {
	t.Fatalf("invalid GO_TEST_TIMEOUT_SCALE: %v", err)
	}
	gracePeriod *= time.Duration(scale)
	}

	// If time allows, increase the termination grace period to 5% of the
	// test's remaining time.
	testTimeout := time.Until(td)
	if gp := testTimeout / 20; gp > gracePeriod {
	gracePeriod = gp
	}

	// When we run commands that execute subprocesses, we want to reserve two
	// grace periods to clean up: one for the delay between the first
	// termination signal being sent (via the Cancel callback when the Context
	// expires) and the process being forcibly terminated (via the WaitDelay
	// field), and a second one for the delay between the process being
	// terminated and the test logging its output for debugging.
	//
	// (We want to ensure that the test process itself has enough time to
	// log the output before it is also terminated.)
	cmdTimeout := testTimeout - 2*gracePeriod

	if cd, ok := ctx.Deadline(); !ok \|\| time.Until(cd) > cmdTimeout {
	// Either ctx doesn't have a deadline, or its deadline would expire
	// after (or too close before) the test has already timed out.
	// Add a shorter timeout so that the test will produce useful output.
	ctx, cancelCtx = context.WithTimeout(ctx, cmdTimeout)
	}
	}
	}

	cmd := exec.CommandContext(ctx, name, args...)
	cmd.Cancel = func() error {
	if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
	// The command timed out due to running too close to the test's deadline.
	// There is no way the test did that intentionally — it's too close to the
	// wire! — so mark it as a test failure. That way, if the test expects the
	// command to fail for some other reason, it doesn't have to distinguish
	// between that reason and a timeout.
	t.Errorf("test timed out while running command: %v", cmd)
	} else {
	// The command is being terminated due to ctx being canceled, but
	// apparently not due to an explicit test deadline that we added.
	// Log that information in case it is useful for diagnosing a failure,
	// but don't actually fail the test because of it.
	t.Logf("%v: terminating command: %v", ctx.Err(), cmd)
	}
	return cmd.Process.Signal(Sigquit)
	}
	cmd.WaitDelay = gracePeriod

	t.Cleanup(func() {
	if cancelCtx != nil {
	cancelCtx()
	}
	if cmd.Process != nil && cmd.ProcessState == nil {
	t.Errorf("command was started, but test did not wait for it to complete: %v", cmd)
	}
	})

	return cmd
	}

	// Command is like exec.Command, but applies the same changes as
	// testenv.CommandContext (with a default Context).
	func Command(t testing.TB, name string, args ...string) *exec.Cmd {
	t.Helper()
	return CommandContext(t, context.Background(), name, args...)
	}