tpl/internal: Sync Go template src to Go 1.20

Updates #10691

tpl/internal/go_templates/testenv/exec.go

@@ -5,12 +5,15 @@
 package testenv
 
 import (
+	"context"
 	"os"
 	"os/exec"
 	"runtime"
+	"strconv"
 	"strings"
 	"sync"
 	"testing"
+	"time"
 )
 
 // HasExec reports whether the current system can start new processes
@@ -71,3 +74,102 @@ func CleanCmdEnv(cmd *exec.Cmd) *exec.Cmd {
 	}
 	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 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...)
+	/*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...)
+}