ignore error in plan shutdown test

The error was being silently dropped before.

There is an interpolation error, because the plan is canceled before
some of the resources can be evaluated. There might be a better way to
handle this in the walk cancellation, but the behavior has not changed.

Make the plan and apply shutdown match implementation-wise

command/apply_test.go

@@ -824,12 +824,11 @@ func TestApply_refresh(t *testing.T) {
 }
 
 func TestApply_shutdown(t *testing.T) {
-	cancelled := false
-	stopped := make(chan struct{})
+	cancelled := make(chan struct{})
+	shutdownCh := make(chan struct{})
 
 	statePath := testTempFile(t)
 	p := testProvider()
-	shutdownCh := make(chan struct{})
 
 	ui := new(cli.MockUi)
 	c := &ApplyCommand{
@@ -841,8 +840,7 @@ func TestApply_shutdown(t *testing.T) {
 	}
 
 	p.StopFn = func() error {
-		close(stopped)
-		cancelled = true
+		close(cancelled)
 		return nil
 	}
 
@@ -858,15 +856,26 @@ func TestApply_shutdown(t *testing.T) {
 			},
 		}, nil
 	}
+
+	var once sync.Once
 	p.ApplyFn = func(
 		*terraform.InstanceInfo,
 		*terraform.InstanceState,
 		*terraform.InstanceDiff) (*terraform.InstanceState, error) {
+
 		// only cancel once
-		if !cancelled {
+		once.Do(func() {
 			shutdownCh <- struct{}{}
-			<-stopped
-		}
+		})
+
+		// Because of the internal lock in the MockProvider, we can't
+		// coordiante directly with the calling of Stop, and making the
+		// MockProvider concurrent is disruptive to a lot of existing tests.
+		// Wait here a moment to help make sure the main goroutine gets to the
+		// Stop call before we exit, or the plan may finish before it can be
+		// canceled.
+		time.Sleep(200 * time.Millisecond)
+
 		return &terraform.InstanceState{
 			ID: "foo",
 			Attributes: map[string]string{
@@ -888,7 +897,9 @@ func TestApply_shutdown(t *testing.T) {
 		t.Fatalf("err: %s", err)
 	}
 
-	if !cancelled {
+	select {
+	case <-cancelled:
+	default:
 		t.Fatal("command not cancelled")
 	}
 

command/plan_test.go

@@ -835,8 +835,8 @@ func TestPlan_detailedExitcode_emptyDiff(t *testing.T) {
 
 func TestPlan_shutdown(t *testing.T) {
 	cancelled := make(chan struct{})
-
 	shutdownCh := make(chan struct{})
+
 	p := testProvider()
 	ui := new(cli.MockUi)
 	c := &PlanCommand{
@@ -880,8 +880,10 @@ func TestPlan_shutdown(t *testing.T) {
 		}, nil
 	}
 
-	if code := c.Run([]string{testFixturePath("apply-shutdown")}); code != 0 {
-		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
+	if code := c.Run([]string{testFixturePath("apply-shutdown")}); code != 1 {
+		// FIXME: we should be able to avoid the error during evaluation
+		// the early exit isn't caught before the interpolation is evaluated
+		t.Fatal(ui.OutputWriter.String())
 	}
 
 	select {