Drop __firstlineno__ on ProxyBase instances

[jcrist]

We don't want to define __firstlineno__ on instances of ProxyBase.

• We don't want to proxy through the original __firstlineno__, since we've updated __module__, so the line numbers would no longer be accurate.
• We don't want to use our __firstlineno__ for the same reason - they map to a different file than __module__.

Dropping this attribute causes tools like inspect.getsourcelines to error appropriately, saying the source code cannot be found. Note that any methods inspected on our proxy classes will still report the original sklearn code (as intended), it's just grabbing the whole class that won't work.

The main place this shows up is some docstring tests in the sklearn repo - previously these were implicitly skipped because getsourcelines would error. The recent metaclass changes led to this not erroring in all python versions, leading to failures in our nightlies.

This PR fixes things so that we drop __firstlineno__ uniformly, leading to the tests to pass/skip in all python versions, reverting to the previous behavior.

[coderabbitai]

📝 Walkthrough

Summary by CodeRabbit

• Bug Fixes
  • Fixed proxy class metadata initialization to properly handle class properties and attributes when modules are reassigned during the creation process. This correction prevents potential metadata inconsistencies that could negatively impact proxy class behavior within the acceleration module, improving system stability and ensuring consistent performance of the proxy mechanism across different operational scenarios.

Walkthrough

The PR modifies ProxyBase.__init_subclass__ in the estimator proxy module to remove the __firstlineno__ attribute from generated proxy classes, preventing the original class's line number metadata from persisting after __module__ reassignment.

Changes

Proxy Class Metadata Cleanup

Layer / File(s)	Summary
Proxy Metadata Handling python/cuml/cuml/accel/estimator_proxy.py	ProxyBase.__init_subclass__ adds a try/except block to delete __firstlineno__ from the proxy class, ensuring generated classes do not retain the original class's line number.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related PRs

• Support subclassing proxy estimators #8041: Also modifies proxy-class creation behavior in estimator_proxy.py with changes to ProxyBase.__init_subclass__ and metadata handling.

Suggested labels

Cython / Python

Suggested reviewers

• csadorf

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main change: removing __firstlineno__ from ProxyBase instances.
Description check	✅ Passed	The description clearly explains the rationale, implementation details, and impact of removing __firstlineno__ from ProxyBase instances.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@python/cuml/cuml/accel/estimator_proxy.py`:
- Around line 246-257: Add a regression test that verifies deletion of
__firstlineno__ on proxy classes: create a proxy class instance (the class
produced by the estimator proxy metaclass in estimator_proxy.py) and assert that
inspect.getsource(proxy_class) raises (e.g., OSError) while
inspect.getsource(proxy_class.some_method) or
inspect.getsource(proxy_instance.some_method) still returns the method source;
this ensures class-level source inspection fails after del cls.__firstlineno__
but method-level lookup remains intact. Include the test alongside existing
estimator_proxy tests and reference the proxy class created by the metaclass and
the cls.__firstlineno__ behavior in the test name/comment.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

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Run ID: 48bbe255-af8c-4159-8677-f4289be825b2

📥 Commits

Reviewing files that changed from the base of the PR and between d8e41af and afde88d.

📒 Files selected for processing (1)

• python/cuml/cuml/accel/estimator_proxy.py

[jcrist]

/merge