Parallel Execution - SupportCodeLibraryBuilder Not Loaded with Externalised Hook Information

[tamil777selvan]

👓 What did you see?

Hooks that are loaded via supportCodeLibraryBuilder encounter an error when using the parallel option in the runCucumber API.

✅ What did you expect to see?

Hooks loaded through supportCodeLibraryBuilder should be properly initialised and accessible, even when parallel mode is enabled.

📦 Which tool/library version are you using?

Cucumber JS - 9.5.1

🔬 How could we reproduce it?

1. Reset supportCodeLibraryBuilder.
2. Import or require the files you want to use.
3. Implement BeforeAll using supportCodeLibraryBuilder.methods.BeforeAll.
4. Finalise supportCodeLibraryBuilder.

Once you've completed the above setup, you can invoke runCucumber with parallel: 0, and it should work as expected because it uses runTime.

However, if you set parallel: 1, you will encounter the following error because it uses the parallel coordinator.

TypeError: Cannot read properties of undefined (reading 'getInvocationParameters')
    at Object.run (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/step_runner.ts:34:43)
    at TestCaseRunner.invokeStep (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/test_case_runner.ts:137:29)
    at TestCaseRunner.runHook (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/test_case_runner.ts:273:23)
    at /Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/test_case_runner.ts:231:29
    at TestCaseRunner.aroundTestStep (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/test_case_runner.ts:170:34)
    at TestCaseRunner.runAttempt (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/test_case_runner.ts:218:18)
    at TestCaseRunner.run (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/test_case_runner.ts:188:40)
    at Worker.runTestCase (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/lib/runtime/parallel/worker.js:115:30)
    at Worker.receiveMessage (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/lib/runtime/parallel/worker.js:97:24)
    at process.<anonymous> (/Users/tamil/Desktop/workspace/cucumber-parallel/node_modules/@cucumber/cucumber/src/runtime/parallel/run_worker.ts:20:8)

📚 Any additional context?

Code Snippet Used:

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[davidjgoss]

Hey @tamil777selvan, sorry for the late reply.

The support code loading for parallel is...a bit weird. We load it on the coordinator (from where we emit the messages about it) and then again on each worker (where the tests are actually going to be run). There's then a kind of sync process so they share the same ids in all places.

So if you jump in via the builder and add a hook on the coordinator only, there'll be a mismatch and thing will break in the way that you've seen.

I'm sure we can figure out a solution though. One of the things I've been looking at under the umbrella of Plugins is an extension point to prepend/append steps and hooks separate to the normal support code loading cycle. Also though, there might be other ways you can inject the behaviour you want besides a hook.

Can you say a bit more about the use case that's driving this?

[tamil777selvan]

Hi @davidjgoss,

This scenario is particularly relevant when integrating WebdriverIO with Cucumber's parallel execution mechanism. When parallel execution is enabled, the WebdriverIO hooks invoked are not processed within the parallel coordinator, resulting in the observed issue.

[davidjgoss]

the WebdriverIO hooks invoked

Could you say a bit more about what these hooks do? i.e. is it user-authored code, or more like wdio plumbing? If you were to put them in a file and add it to the require option, would that break in some way?

(I suspect there is some overlap with #2156 here.)

[tamil777selvan]

@davidjgoss, these codes are provided by users and are integrated into Cucumber hooks through the support code library within the wdio-cucumber-framework. Even if we attempt to isolate this hook in a separate file and import it, it may not function as expected. The reason for this is that WebDriverIO hooks have their own names, and these names are internally mapped to corresponding Cucumber hooks.

For example, the beforeScenario WebDriverIO hook aligns with the before Cucumber hook.

This seems quite similar to the previous issue, as both cases involve the need to load custom hooks for parallel execution.

[davidjgoss]

Thanks for the detail!

For this to work we have to find a way to have these user-authored hooks register on both the coordinator (parent) process and the worker processes.

I assume we don't have this problem for steps because users are calling the Cucumber Given, When, Then functions directly and we're loading that code via the require and/or import options? Would this be an option for the hooks too (e.g. use Before, BeforeAll, BeforeStep etc) or do the hooks get some special wdio-specific context/args passed to them?