internal/testenv/exec.go - tools - 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"
 	"flag"
 	"os"
 	"os/exec"
 	"reflect"
 	"runtime"
 	"strconv"
 	"sync"
 	"testing"
 	"time"
 )

 // HasExec reports whether the current system can start new processes
 // using os.StartProcess or (more commonly) exec.Command.
 func HasExec() bool {
 	switch runtime.GOOS {
 	case "aix",
 		"android",
 		"darwin",
 		"dragonfly",
 		"freebsd",
 		"illumos",
 		"linux",
 		"netbsd",
 		"openbsd",
 		"plan9",
 		"solaris",
 		"windows":
 		// Known OS that isn't ios or wasm; assume that exec works.
 		return true

 	case "ios", "js", "wasip1":
 		// 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 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.
 		fallthrough

 	default:
 		tryExecOnce.Do(func() {
 			exe, err := os.Executable()
 			if err != nil {
 				return
 			}
 			if flag.Lookup("test.list") == nil {
 				// We found the executable, but we don't know how to run it in a way
 				// that should succeed without side-effects. Just forget it.
 				return
 			}
 			// We know that a test executable exists and can run, because we're
 			// running it now. Use it to check for overall exec support, but be sure
 			// to remove any environment variables that might trigger non-default
 			// behavior in a custom TestMain.
 			cmd := exec.Command(exe, "-test.list=^$")
 			cmd.Env = []string{}
 			if err := cmd.Run(); err == nil {
 				tryExecOk = true
 			}
 		})
 		return tryExecOk
 	}
 }

 var (
 	tryExecOnce sync.Once
 	tryExecOk   bool
 )

 // NeedsExec checks that the current system can start new processes
 // using os.StartProcess or (more commonly) exec.Command.
 // If not, NeedsExec calls t.Skip with an explanation.
 func NeedsExec(t testing.TB) {
 	if !HasExec() {
 		t.Skipf("skipping test: cannot exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
 	}
 }

 // CommandContext is like exec.CommandContext, but:
 //   - skips t if the platform does not support os/exec,
 //   - if supported, sends SIGQUIT instead of SIGKILL in its Cancel function
 //   - if the test has a deadline, adds a Context timeout and (if supported) WaitDelay
 //     for an arbitrary grace period before the test's deadline expires,
 //   - if Cmd has the Cancel field, fails the test if the command is canceled
 //     due to the test's deadline, and
 //   - if supported, 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()
 	NeedsExec(t)

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

 	if td, ok := Deadline(t); 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 becween the process being
 		// terminated and 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...)

 	// Use reflection to set the Cancel and WaitDelay fields, if present.
 	// TODO(bcmills): When we no longer support Go versions below 1.20,
 	// remove the use of reflect and assume that the fields are always present.
 	rc := reflect.ValueOf(cmd).Elem()

 	if rCancel := rc.FieldByName("Cancel"); rCancel.IsValid() {
 		rCancel.Set(reflect.ValueOf(func() error {
 			if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
 				// The command timed out due to running too close to the test's deadline
 				// (because we specifically set a shorter Context deadline for that
 				// above). 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)
 		}))
 	}

 	if rWaitDelay := rc.FieldByName("WaitDelay"); rWaitDelay.IsValid() {
 		rWaitDelay.Set(reflect.ValueOf(gracePeriod))
 	}

 	// t.Cleanup was added in Go 1.14; for earlier Go versions,
 	// we just let the Context leak.
 	type Cleanupper interface {
 		Cleanup(func())
 	}
 	if ct, ok := t.(Cleanupper); ok {
 		ct.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"
	"flag"
	"os"
	"os/exec"
	"reflect"
	"runtime"
	"strconv"
	"sync"
	"testing"
	"time"
	)

	// HasExec reports whether the current system can start new processes
	// using os.StartProcess or (more commonly) exec.Command.
	func HasExec() bool {
	switch runtime.GOOS {
	case "aix",
	"android",
	"darwin",
	"dragonfly",
	"freebsd",
	"illumos",
	"linux",
	"netbsd",
	"openbsd",
	"plan9",
	"solaris",
	"windows":
	// Known OS that isn't ios or wasm; assume that exec works.
	return true

	case "ios", "js", "wasip1":
	// 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 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.
	fallthrough

	default:
	tryExecOnce.Do(func() {
	exe, err := os.Executable()
	if err != nil {
	return
	}
	if flag.Lookup("test.list") == nil {
	// We found the executable, but we don't know how to run it in a way
	// that should succeed without side-effects. Just forget it.
	return
	}
	// We know that a test executable exists and can run, because we're
	// running it now. Use it to check for overall exec support, but be sure
	// to remove any environment variables that might trigger non-default
	// behavior in a custom TestMain.
	cmd := exec.Command(exe, "-test.list=^$")
	cmd.Env = []string{}
	if err := cmd.Run(); err == nil {
	tryExecOk = true
	}
	})
	return tryExecOk
	}
	}

	var (
	tryExecOnce sync.Once
	tryExecOk bool
	)

	// NeedsExec checks that the current system can start new processes
	// using os.StartProcess or (more commonly) exec.Command.
	// If not, NeedsExec calls t.Skip with an explanation.
	func NeedsExec(t testing.TB) {
	if !HasExec() {
	t.Skipf("skipping test: cannot exec subprocess on %s/%s", runtime.GOOS, runtime.GOARCH)
	}
	}

	// CommandContext is like exec.CommandContext, but:
	// - skips t if the platform does not support os/exec,
	// - if supported, sends SIGQUIT instead of SIGKILL in its Cancel function
	// - if the test has a deadline, adds a Context timeout and (if supported) WaitDelay
	// for an arbitrary grace period before the test's deadline expires,
	// - if Cmd has the Cancel field, fails the test if the command is canceled
	// due to the test's deadline, and
	// - if supported, 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()
	NeedsExec(t)

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

	if td, ok := Deadline(t); 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 becween the process being
	// terminated and 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...)

	// Use reflection to set the Cancel and WaitDelay fields, if present.
	// TODO(bcmills): When we no longer support Go versions below 1.20,
	// remove the use of reflect and assume that the fields are always present.
	rc := reflect.ValueOf(cmd).Elem()

	if rCancel := rc.FieldByName("Cancel"); rCancel.IsValid() {
	rCancel.Set(reflect.ValueOf(func() error {
	if cancelCtx != nil && ctx.Err() == context.DeadlineExceeded {
	// The command timed out due to running too close to the test's deadline
	// (because we specifically set a shorter Context deadline for that
	// above). 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)
	}))
	}

	if rWaitDelay := rc.FieldByName("WaitDelay"); rWaitDelay.IsValid() {
	rWaitDelay.Set(reflect.ValueOf(gracePeriod))
	}

	// t.Cleanup was added in Go 1.14; for earlier Go versions,
	// we just let the Context leak.
	type Cleanupper interface {
	Cleanup(func())
	}
	if ct, ok := t.(Cleanupper); ok {
	ct.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...)
	}