Filter glue class candidates before loading

[laeubi]

🤔 What's the problem you're trying to solve?

If I use the Runtime.builder() I can supply a classloader withClassLoader but the actuall class scanning can not be customized.

✨ What's your proposed solution?

There should be a way to injects some kind of GlueClassScanner that allows to plug in different techniques.
Currently always ClasspathScanner is used with no way to customize that.

⛏ Have you considered any alternatives or workarounds?

No response

📚 Any additional context?

No response

[mpkorstanje]

What are won class scanners? And what problem does that solve?

[laeubi]

What are won class scanners?

won = on

And what problem does that solve?

See description. Currently there is no way to control how/what is scanned by cucumber and I need to do some tricks in the classloader, but still cucumber controls how/what is scanned (see #3135 for one issue I encountered).

So at best ClasspathScanner would be an interface (and the ClasspathScanner becomes DefaultClasspathScanner used if nothing is given) and I can pass in an own implementation.

[mpkorstanje]

Okay. But if #3115 is solved, what problems remain?

[laeubi]

Okay. But if #3115 is solved, what problems remain?

While it handles the situation, it would much better if I could just not try to load the problematic classes at all. So lets assume I have a rule that all my Step classes must end with "Steps" (similar to surefire defaults that all test must end with Test), cucumber currently scans ALL classes for annotations (what might be quite expensive on big classpath). Today I can only limit it by a glue package name, but would it not be nicer if I can filter it and even then not scan useless things?

This is of course a very simple example, but you can image anything, e.g. it must be a special package prefix AND a suffix and so on, maybe different classes depending on OS you are running...

This is quite similar to

• Add API to Manually Register Step Classes #3118

So bottom line is: Sometimes a custom discover strategy is useful :-)

[mpkorstanje]

Okay. Then you are asking for filtering in the class path scanner, before the class is loaded. And a way to communicate to Cucumber what your candidate step definition classes look like.

Something like https://github.com/junit-team/junit-framework/blob/main/junit-platform-commons/src/main/java/org/junit/platform/commons/support/scanning/ClasspathScanner.java. The class and resource filter arguments are applied pre- and post loading.

Note: This happens to be an interface but that is coincidental to the request. This is an interface to facilitate scanning on Android which is significantly different.

[laeubi]

Okay. Then you are asking for filtering in the class path scanner, before the class is loaded

At least yes! I wont mind to defer the whole scanning process at all. In older cucumber versions there was once a ClassFinder interface one could implement but I can't find something similar in modern cucumber-jvm versions.