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Diffstat (limited to 'internal/testenv/exec.go')
-rw-r--r-- | internal/testenv/exec.go | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/internal/testenv/exec.go b/internal/testenv/exec.go new file mode 100644 index 000000000..f103ad9d8 --- /dev/null +++ b/internal/testenv/exec.go @@ -0,0 +1,149 @@ +// 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" + "os" + "os/exec" + "reflect" + "runtime" + "strconv" + "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 "js", "ios": + return false + } + return true +} + +// 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...) +} |