[Core] Add StepDefinedEvent

[timtebeek]

Summary

Adds a StepDefinedEvent to replace the StepDefinitionReporter plugin interface.

Details

Publish an event from Glue.addStepDefinition, as Runner.reportStepDefinitions is called before step definition classes are instantiated, which fails to pick up on lambda based steps.

Motivation and Context

Provide an event to listen for steps being registered, so all steps registrations are available, instead of only the annotation based step definitions.
#1633

How Has This Been Tested?

Not yet; Change seems small.

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist:

• I've added tests for my code.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

[coveralls]

Coverage increased (+0.005%) to 85.95% when pulling 3776a75 on timtebeek:step-defined-event into 75083d2 on cucumber:master.

[mpkorstanje]

Looks good. Bit light on the tests so far.

We do have a memory leak. Lambda step definitions internally have a reference to their closure via Java8StepDefinition.body. Normally this would be GC'd when the world is disposed of. However because we now push these step definitions onto the event bus this is no longer guaranteed. For instance, the canonical order event bus will hold on to all of them.

Ideally when removing the scenario scoped step definitions from the glue, we also remove their reference to the world.

It would be okay to add extra methods to StepDefinition, the interface is not part of the public API, but I would prefer deprecating isScenarioScoped in favor of an ScenarioScoped interface that implements a disposeScenarioScope method.

[timtebeek]

Hmm; trying to see if I understand you correctly; You want to (for instance) add a disposeScenarioScope method in Java8StepDefinition which is called in Glue.removeScenariosScopedStepDefinitions(Map<String, StepDefinition>) ? And have that method assign null to the body field to remove the reference?

I'll be off for a few days, so will only be able to pick this up on the weekend..

[timtebeek]

As for the test coverage; Agree it's "parse". Functionally the only new line is: bus.send(new StepDefinedEvent(bus.getTime(), bus.getTimeMillis(), stepDefinition));, but I didn't think it sensible to call it in Glue and verify that it's called in GlueTest. We've both seen waaay too much of that test pattern applied in our shared working history. ;)

[mpkorstanje]

I was thinking of an integration test that creates a backend with 2 steps. Then run two scenarios with those two steps and check that we see 3 events emitted. There is utility class that makes it relatively easy to setup.

But I'll have to check.

Hmm; trying to see if I understand you correctly; You want to (for instance) add a disposeScenarioScope method in Java8StepDefinition which is called in Glue.removeScenariosScopedStepDefinitions(Map<String, StepDefinition>) ? And have that method assign null to the body field to remove the reference?

Exactly.

[mpkorstanje]

For testing this functionality you can find some examples in RuntimeTest. Adding an extra test there should be fine. I reckon something like this should do, it's a bit messy but should serve to illustrate the point.

        final CucumberFeature feature = feature("test.feature", "" +
            "Feature: feature name\n" +
            "  Scenario: scenario name\n" +
            "    When s\n");

        Plugin plugin = new ConcurrentEventListener() {
            @Override
            public void setEventPublisher(EventPublisher publisher) {
                // Capture some events here.                
            }
        };
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        final Backend mock = new Backend() {
            
            @Override
            public void loadGlue(Glue glue, List<URI> gluePaths) {
                // Register some regular glue here        
            }

            @Override
            public void buildWorld() {
                // Register some scenario scoped glue here.
            }

            @Override
            public void disposeWorld() {

            }

            @Override
            public List<String> getSnippet(PickleStep step, String keyword, FunctionNameGenerator functionNameGenerator) {
                return emptyList();
            }
        };

        BackendSupplier backendSupplier = new BackendSupplier() {
            @Override
            public Collection<? extends Backend> get() {
                return singletonList(mock);
            }
        };
        FeatureSupplier featureSupplier = new FeatureSupplier() {
            @Override
            public List<CucumberFeature> get() {
                return singletonList(feature);
            }
        };
        Runtime.builder()
            .withBackendSupplier(backendSupplier)
            .withAdditionalPlugins(plugin)
            .withResourceLoader(new ClasspathResourceLoader(classLoader))
            .withEventBus(new TimeServiceEventBus(new TimeServiceStub(0)))
            .withFeatureSupplier(featureSupplier)
            .build()
            .run();
           // Check if the plugin captured the expected events here.

[timtebeek]

@mpkorstanje Thanks for the hint on testing. I'm still having some trouble filling in the blank here:
public void buildWorld() { // Register some scenario scoped glue here.
The only examples of registering Lambda based steps I see are in the Java/Java8 modules; the approach there is hard to replicate in core due to missing classes. Any suggestions there?

I've added ScenarioScoped changes in 81f2c98 , I hope that's what you intended!

[mpkorstanje]

A mocked step definition will do. As long as it isScenarioScoped returns true.

[timtebeek]

Hmm; Looked into it again, but really stuck on the new Backend() { ... } details; Just too unfamiliar with the (test) internals I suppose. Would love to see this work; but I'm lost as to how.

[mpkorstanje]

I've pushed a commit. It's a bit of a hack job but should get the point across.

[mpkorstanje]

I should look into making some proper test implementations of the components I just mocked.

[timtebeek]

Awesome, thanks! Had been eyeing the TestBackendSupplier, but wouldn't have worked out I'd need anything like MockedScenarioScopedStepDefinition or MockedStepDefinition on my own.. thanks a lot!
Anything else we need to cross off before we can consider a merge?

[mpkorstanje]

Its good as is. But I am going to try and sneak in a redactor or two. There is an emerging pattern here that calls for some reusable test components.

You know the ratchet mechanism bring and keep quality up. May take a bit of time. It's been busy since we last spoke. There is less time for OSS now.

[timtebeek]

Ok thanks for helping out; If I can help in any way let me know; all the best there! Miss working together in Amsterdam.. :)

[aslakhellesoy]

Hi @timtebeek,

Thanks for your making your first contribution to Cucumber, and welcome to the Cucumber committers team! You can now push directly to this repo and all other repos under the cucumber organization! 🍾

In return for this generous offer we hope you will:

• ✅ Continue to use branches and pull requests. When someone on the core team approves a pull request (yours or someone else's), you're welcome to merge it yourself.
• 💚 Commit to setting a good example by following and upholding our code of conduct in your interactions with other collaborators and users.
• 💬 Join the community Slack channel to meet the rest of the team and make yourself at home.
• ℹ️ Don't feel obliged to help, just do what you can if you have the time and the energy.
• 🙋 Ask if you need anything. We're looking for feedback about how to make the project more welcoming, so please tell us!

On behalf of the Cucumber core team,
Aslak Hellesøy
Creator of Cucumber

[mpkorstanje]

Cheers. No worries!

[timtebeek]

Awesome, great to see this merged! I'll update my unused steps plugin blog post to include these Java 8 steps. Should I start a PR to contribute that as well? It's small, has no dependencies and could be useful plus serve as example.

[mpkorstanje]

Would not mind seeing it. Though the json format is problematic. Almost impossible to evolve on. Perhaps we can have a look at that.

[lock]

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