Do not run lifecycle hooks with expired context (#875)

Currently, the lifecycle hooks are still run even when the context
passed as parameter to Start/Stop calls has expired/DeadlineExceeded.

This changes the fx lifecycle hook execution loop to check for expired
context before executing each hook, and bailing out of the exec loop
upon encountering context expiration.

Refs GO-1026.

internal/lifecycle/lifecycle.go

@@ -77,6 +77,11 @@ func (l *Lifecycle) Start(ctx context.Context) error {
 	l.mu.Unlock()
 
 	for _, hook := range l.hooks {
+		// if ctx has cancelled, bail out of the loop.
+		if err := ctx.Err(); err != nil {
+			return err
+		}
+
 		if hook.OnStart != nil {
 			l.mu.Lock()
 			l.runningHook = hook
@@ -131,6 +136,9 @@ func (l *Lifecycle) Stop(ctx context.Context) error {
 	// Run backward from last successful OnStart.
 	var errs []error
 	for ; l.numStarted > 0; l.numStarted-- {
+		if err := ctx.Err(); err != nil {
+			return err
+		}
 		hook := l.hooks[l.numStarted-1]
 		if hook.OnStop == nil {
 			continue

internal/lifecycle/lifecycle_test.go

@@ -119,6 +119,30 @@ func TestLifecycleStart(t *testing.T) {
 		assert.Equal(t, 2, starterCount, "expected the first and second starter to execute")
 		assert.Equal(t, 1, stopperCount, "expected the first stopper to execute since the second starter failed")
 	})
+
+	t.Run("DoNotRunStartHooksWithExpiredCtx", func(t *testing.T) {
+		t.Parallel()
+
+		l := New(testLogger(t), fxclock.System)
+		l.Append(Hook{
+			OnStart: func(context.Context) error {
+				assert.Fail(t, "this hook should not run")
+				return nil
+			},
+			OnStop: func(context.Context) error {
+				assert.Fail(t, "this hook should not run")
+				return nil
+			},
+		})
+		ctx, cancel := context.WithCancel(context.Background())
+		cancel()
+		err := l.Start(ctx)
+		require.Error(t, err)
+		// Note: Stop does not return an error here because no hooks
+		// have been started, so we don't end up any of the corresponding
+		// stop hooks.
+		require.NoError(t, l.Stop(ctx))
+	})
 }
 
 func TestLifecycleStop(t *testing.T) {
@@ -247,6 +271,26 @@ func TestLifecycleStop(t *testing.T) {
 		assert.Equal(t, err, l.Start(context.Background()))
 		l.Stop(context.Background())
 	})
+
+	t.Run("DoNotRunStopHooksWithExpiredCtx", func(t *testing.T) {
+		t.Parallel()
+
+		l := New(testLogger(t), fxclock.System)
+		l.Append(Hook{
+			OnStart: func(context.Context) error {
+				return nil
+			},
+			OnStop: func(context.Context) error {
+				assert.Fail(t, "this hook should not run")
+				return nil
+			},
+		})
+		ctx, cancel := context.WithCancel(context.Background())
+		err := l.Start(ctx)
+		require.NoError(t, err)
+		cancel()
+		require.Error(t, l.Stop(ctx))
+	})
 }
 
 func TestHookRecordsFormat(t *testing.T) {