add event loop tests

Signed-off-by: Alex Goodman <wagoodman@gmail.com>

cmd/event_loop.go

@@ -4,7 +4,6 @@ import (
 	"errors"
 	"os"
 
-	"github.com/anchore/syft/syft"
 	"github.com/anchore/syft/internal/log"
 	"github.com/anchore/syft/internal/ui"
 	"github.com/hashicorp/go-multierror"
@@ -14,9 +13,12 @@ import (
 // eventLoop listens to worker errors (from execution path), worker events (from a partybus subscription), and
 // signal interrupts. Is responsible for handling each event relative to a given UI an to coordinate eventing until
 // an eventual graceful exit.
-func eventLoop(workerErrs <-chan error, signals <-chan os.Signal, subscription *partybus.Subscription, ux ui.UI) error {
+// nolint:gocognit
+func eventLoop(workerErrs <-chan error, signals <-chan os.Signal, subscription *partybus.Subscription, ux ui.UI, cleanupFn func()) error {
+	defer cleanupFn()
 	events := subscription.Events()
-	if err := setupUI(subscription.Unsubscribe, ux); err != nil {
+	var err error
+	if ux, err = setupUI(subscription.Unsubscribe, ux); err != nil {
 		return err
 	}
 
@@ -33,7 +35,11 @@ func eventLoop(workerErrs <-chan error, signals <-chan os.Signal, subscription *
 				continue
 			}
 			if err != nil {
-				retErr = err
+				// capture the error from the worker and unsubscribe to complete a graceful shutdown
+				retErr = multierror.Append(retErr, err)
+				if err := subscription.Unsubscribe(); err != nil {
+					retErr = multierror.Append(retErr, err)
+				}
 			}
 		case e, isOpen := <-events:
 			if !isOpen {
@@ -54,9 +60,12 @@ func eventLoop(workerErrs <-chan error, signals <-chan os.Signal, subscription *
 			// ignore further results from any event source and exit ASAP, but ensure that all cache is cleaned up.
 			// we ignore further errors since cleaning up the tmp directories will affect running catalogers that are
 			// reading/writing from/to their nested temp dirs. This is acceptable since we are bailing without result.
+
+			// TODO: potential future improvement would be to pass context into workers with a cancel function that is
+			// to the event loop. In this way we can have a more controlled shutdown even at the most nested levels
+			// of processing.
 			events = nil
 			workerErrs = nil
-			syft.Cleanup()
 		}
 	}
 
@@ -67,14 +76,15 @@ func eventLoop(workerErrs <-chan error, signals <-chan os.Signal, subscription *
 	return retErr
 }
 
-func setupUI(unsubscribe func() error, ux ui.UI) error {
+func setupUI(unsubscribe func() error, ux ui.UI) (ui.UI, error) {
 	if err := ux.Setup(unsubscribe); err != nil {
+		// replace the existing UI with a (simpler) logger UI
 		ux = ui.NewLoggerUI()
 		if err := ux.Setup(unsubscribe); err != nil {
 			// something is very wrong, bail.
-			return err
+			return ux, err
 		}
 		log.Errorf("unable to setup given UI, falling back to logger: %+v", err)
 	}
-	return nil
+	return ux, nil
 }

cmd/event_loop_test.go

@@ -0,0 +1,455 @@
+package cmd
+
+import (
+	"fmt"
+	"os"
+	"syscall"
+	"testing"
+	"time"
+
+	"github.com/anchore/syft/internal/ui"
+	"github.com/anchore/syft/syft/event"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+	"github.com/wagoodman/go-partybus"
+)
+
+var _ ui.UI = (*uiMock)(nil)
+
+type uiMock struct {
+	t           *testing.T
+	finalEvent  partybus.Event
+	unsubscribe func() error
+	mock.Mock
+}
+
+func (u *uiMock) Setup(unsubscribe func() error) error {
+	u.t.Logf("UI Setup called")
+	u.unsubscribe = unsubscribe
+	return u.Called(unsubscribe).Error(0)
+}
+
+func (u *uiMock) Handle(event partybus.Event) error {
+	u.t.Logf("UI Handle called: %+v", event.Type)
+	if event == u.finalEvent {
+		assert.NoError(u.t, u.unsubscribe())
+	}
+	return u.Called(event).Error(0)
+}
+
+func (u *uiMock) Teardown() error {
+	u.t.Logf("UI Teardown called")
+	return u.Called().Error(0)
+}
+
+func Test_eventLoop_gracefulExit(t *testing.T) {
+	test := func(t *testing.T) {
+
+		testBus := partybus.NewBus()
+		subscription := testBus.Subscribe()
+		t.Cleanup(testBus.Close)
+
+		finalEvent := partybus.Event{
+			Type: event.PresenterReady,
+		}
+
+		worker := func() <-chan error {
+			ret := make(chan error)
+			go func() {
+				t.Log("worker running")
+				// send an empty item (which is ignored) ensuring we've entered the select statement,
+				// then close (a partial shutdown).
+				ret <- nil
+				t.Log("worker sent nothing")
+				close(ret)
+				t.Log("worker closed")
+				// do the other half of the shutdown
+				testBus.Publish(finalEvent)
+				t.Log("worker published final event")
+			}()
+			return ret
+		}
+
+		signaler := func() <-chan os.Signal {
+			return nil
+		}
+
+		ux := &uiMock{
+			t:          t,
+			finalEvent: finalEvent,
+		}
+
+		// ensure the mock sees at least the final event
+		ux.On("Handle", finalEvent).Return(nil)
+		// ensure the mock sees basic setup/teardown events
+		ux.On("Setup", mock.AnythingOfType("func() error")).Return(nil)
+		ux.On("Teardown").Return(nil)
+
+		var cleanupCalled bool
+		cleanupFn := func() {
+			t.Log("cleanup called")
+			cleanupCalled = true
+		}
+
+		assert.NoError(t,
+			eventLoop(
+				worker(),
+				signaler(),
+				subscription,
+				ux,
+				cleanupFn,
+			),
+		)
+
+		assert.True(t, cleanupCalled, "cleanup function not called")
+		ux.AssertExpectations(t)
+	}
+
+	// if there is a bug, then there is a risk of the event loop never returning
+	testWithTimeout(t, 5*time.Second, test)
+}
+
+func Test_eventLoop_workerError(t *testing.T) {
+	test := func(t *testing.T) {
+
+		testBus := partybus.NewBus()
+		subscription := testBus.Subscribe()
+		t.Cleanup(testBus.Close)
+
+		workerErr := fmt.Errorf("worker error")
+
+		worker := func() <-chan error {
+			ret := make(chan error)
+			go func() {
+				t.Log("worker running")
+				// send an empty item (which is ignored) ensuring we've entered the select statement,
+				// then close (a partial shutdown).
+				ret <- nil
+				t.Log("worker sent nothing")
+				ret <- workerErr
+				t.Log("worker sent error")
+				close(ret)
+				t.Log("worker closed")
+				// note: NO final event is fired
+			}()
+			return ret
+		}
+
+		signaler := func() <-chan os.Signal {
+			return nil
+		}
+
+		ux := &uiMock{
+			t: t,
+		}
+
+		// ensure the mock sees basic setup/teardown events
+		ux.On("Setup", mock.AnythingOfType("func() error")).Return(nil)
+		ux.On("Teardown").Return(nil)
+
+		var cleanupCalled bool
+		cleanupFn := func() {
+			t.Log("cleanup called")
+			cleanupCalled = true
+		}
+
+		// ensure we see an error returned
+		assert.ErrorIs(t,
+			eventLoop(
+				worker(),
+				signaler(),
+				subscription,
+				ux,
+				cleanupFn,
+			),
+			workerErr,
+			"should have seen a worker error, but did not",
+		)
+
+		assert.True(t, cleanupCalled, "cleanup function not called")
+		ux.AssertExpectations(t)
+	}
+
+	// if there is a bug, then there is a risk of the event loop never returning
+	testWithTimeout(t, 5*time.Second, test)
+}
+
+func Test_eventLoop_unsubscribeError(t *testing.T) {
+	test := func(t *testing.T) {
+
+		testBus := partybus.NewBus()
+		subscription := testBus.Subscribe()
+		t.Cleanup(testBus.Close)
+
+		finalEvent := partybus.Event{
+			Type: event.PresenterReady,
+		}
+
+		worker := func() <-chan error {
+			ret := make(chan error)
+			go func() {
+				t.Log("worker running")
+				// send an empty item (which is ignored) ensuring we've entered the select statement,
+				// then close (a partial shutdown).
+				ret <- nil
+				t.Log("worker sent nothing")
+				close(ret)
+				t.Log("worker closed")
+				// do the other half of the shutdown
+				testBus.Publish(finalEvent)
+				t.Log("worker published final event")
+			}()
+			return ret
+		}
+
+		signaler := func() <-chan os.Signal {
+			return nil
+		}
+
+		ux := &uiMock{
+			t:          t,
+			finalEvent: finalEvent,
+		}
+
+		// ensure the mock sees at least the final event... note the unsubscribe error here
+		ux.On("Handle", finalEvent).Return(partybus.ErrUnsubscribe)
+		// ensure the mock sees basic setup/teardown events
+		ux.On("Setup", mock.AnythingOfType("func() error")).Return(nil)
+		ux.On("Teardown").Return(nil)
+
+		var cleanupCalled bool
+		cleanupFn := func() {
+			t.Log("cleanup called")
+			cleanupCalled = true
+		}
+
+		// unsubscribe errors should be handled and ignored, not propagated. We are additionally asserting that
+		// this case is handled as a controlled shutdown (this test should not timeout)
+		assert.NoError(t,
+			eventLoop(
+				worker(),
+				signaler(),
+				subscription,
+				ux,
+				cleanupFn,
+			),
+		)
+
+		assert.True(t, cleanupCalled, "cleanup function not called")
+		ux.AssertExpectations(t)
+	}
+
+	// if there is a bug, then there is a risk of the event loop never returning
+	testWithTimeout(t, 5*time.Second, test)
+}
+
+func Test_eventLoop_handlerError(t *testing.T) {
+	test := func(t *testing.T) {
+
+		testBus := partybus.NewBus()
+		subscription := testBus.Subscribe()
+		t.Cleanup(testBus.Close)
+
+		finalEvent := partybus.Event{
+			Type:  event.PresenterReady,
+			Error: fmt.Errorf("unable to create presenter"),
+		}
+
+		worker := func() <-chan error {
+			ret := make(chan error)
+			go func() {
+				t.Log("worker running")
+				// send an empty item (which is ignored) ensuring we've entered the select statement,
+				// then close (a partial shutdown).
+				ret <- nil
+				t.Log("worker sent nothing")
+				close(ret)
+				t.Log("worker closed")
+				// do the other half of the shutdown
+				testBus.Publish(finalEvent)
+				t.Log("worker published final event")
+			}()
+			return ret
+		}
+
+		signaler := func() <-chan os.Signal {
+			return nil
+		}
+
+		ux := &uiMock{
+			t:          t,
+			finalEvent: finalEvent,
+		}
+
+		// ensure the mock sees at least the final event... note the event error is propagated
+		ux.On("Handle", finalEvent).Return(finalEvent.Error)
+		// ensure the mock sees basic setup/teardown events
+		ux.On("Setup", mock.AnythingOfType("func() error")).Return(nil)
+		ux.On("Teardown").Return(nil)
+
+		var cleanupCalled bool
+		cleanupFn := func() {
+			t.Log("cleanup called")
+			cleanupCalled = true
+		}
+
+		// handle errors SHOULD propagate the event loop. We are additionally asserting that this case is
+		// handled as a controlled shutdown (this test should not timeout)
+		assert.ErrorIs(t,
+			eventLoop(
+				worker(),
+				signaler(),
+				subscription,
+				ux,
+				cleanupFn,
+			),
+			finalEvent.Error,
+			"should have seen a event error, but did not",
+		)
+
+		assert.True(t, cleanupCalled, "cleanup function not called")
+		ux.AssertExpectations(t)
+	}
+
+	// if there is a bug, then there is a risk of the event loop never returning
+	testWithTimeout(t, 5*time.Second, test)
+}
+
+func Test_eventLoop_signalsStopExecution(t *testing.T) {
+	test := func(t *testing.T) {
+
+		testBus := partybus.NewBus()
+		subscription := testBus.Subscribe()
+		t.Cleanup(testBus.Close)
+
+		worker := func() <-chan error {
+			// the worker will never return work and the event loop will always be waiting...
+			return make(chan error)
+		}
+
+		signaler := func() <-chan os.Signal {
+			ret := make(chan os.Signal)
+			go func() {
+				ret <- syscall.SIGINT
+				// note: we do NOT close the channel to ensure the event loop does not depend on that behavior to exit
+			}()
+			return ret
+		}
+
+		ux := &uiMock{
+			t: t,
+		}
+
+		// ensure the mock sees basic setup/teardown events
+		ux.On("Setup", mock.AnythingOfType("func() error")).Return(nil)
+		ux.On("Teardown").Return(nil)
+
+		var cleanupCalled bool
+		cleanupFn := func() {
+			t.Log("cleanup called")
+			cleanupCalled = true
+		}
+
+		assert.NoError(t,
+			eventLoop(
+				worker(),
+				signaler(),
+				subscription,
+				ux,
+				cleanupFn,
+			),
+		)
+
+		assert.True(t, cleanupCalled, "cleanup function not called")
+		ux.AssertExpectations(t)
+	}
+
+	// if there is a bug, then there is a risk of the event loop never returning
+	testWithTimeout(t, 5*time.Second, test)
+}
+
+func Test_eventLoop_uiTeardownError(t *testing.T) {
+	test := func(t *testing.T) {
+
+		testBus := partybus.NewBus()
+		subscription := testBus.Subscribe()
+		t.Cleanup(testBus.Close)
+
+		finalEvent := partybus.Event{
+			Type: event.PresenterReady,
+		}
+
+		worker := func() <-chan error {
+			ret := make(chan error)
+			go func() {
+				t.Log("worker running")
+				// send an empty item (which is ignored) ensuring we've entered the select statement,
+				// then close (a partial shutdown).
+				ret <- nil
+				t.Log("worker sent nothing")
+				close(ret)
+				t.Log("worker closed")
+				// do the other half of the shutdown
+				testBus.Publish(finalEvent)
+				t.Log("worker published final event")
+			}()
+			return ret
+		}
+
+		signaler := func() <-chan os.Signal {
+			return nil
+		}
+
+		ux := &uiMock{
+			t:          t,
+			finalEvent: finalEvent,
+		}
+
+		teardownError := fmt.Errorf("sorry, dave, the UI doesn't want to be torn down")
+
+		// ensure the mock sees at least the final event... note the event error is propagated
+		ux.On("Handle", finalEvent).Return(nil)
+		// ensure the mock sees basic setup/teardown events
+		ux.On("Setup", mock.AnythingOfType("func() error")).Return(nil)
+		ux.On("Teardown").Return(teardownError)
+
+		var cleanupCalled bool
+		cleanupFn := func() {
+			t.Log("cleanup called")
+			cleanupCalled = true
+		}
+
+		// ensure we see an error returned
+		assert.ErrorIs(t,
+			eventLoop(
+				worker(),
+				signaler(),
+				subscription,
+				ux,
+				cleanupFn,
+			),
+			teardownError,
+			"should have seen a UI teardown error, but did not",
+		)
+
+		assert.True(t, cleanupCalled, "cleanup function not called")
+		ux.AssertExpectations(t)
+	}
+
+	// if there is a bug, then there is a risk of the event loop never returning
+	testWithTimeout(t, 5*time.Second, test)
+}
+
+func testWithTimeout(t *testing.T, timeout time.Duration, test func(*testing.T)) {
+	done := make(chan bool)
+	go func() {
+		test(t)
+		done <- true
+	}()
+
+	select {
+	case <-time.After(timeout):
+		t.Fatal("test timed out")
+	case <-done:
+	}
+}

cmd/packages.go

@@ -189,6 +189,7 @@ func packagesExec(_ *cobra.Command, args []string) error {
 		setupSignals(),
 		eventSubscription,
 		ui.Select(appConfig.CliOptions.Verbosity > 0, appConfig.Quiet),
+		syft.Cleanup,
 	)
 }
 

cmd/power_user.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"sync"
 
+	"github.com/anchore/syft/syft"
+
 	"github.com/anchore/syft/internal"
 	"github.com/anchore/syft/internal/bus"
 	"github.com/anchore/syft/internal/log"
@@ -68,6 +70,7 @@ func powerUserExec(_ *cobra.Command, args []string) error {
 		setupSignals(),
 		eventSubscription,
 		ui.Select(appConfig.CliOptions.Verbosity > 0, appConfig.Quiet),
+		syft.Cleanup,
 	)
 }