[py] Fix type annotation errors in service.py

[NoStory-py]

User description

Fixed the instance variable log_output by properly annotating it as int | IOBase | None. Removed unnecessary #type: ignore comments where mypy requires them.

🔗 Related Issues

Partially addresses #15697

💥 What does this PR do?

Fixes mypy type annotation errors in
selenium/webdriver/common/service.py:

• Annotated self.log_output as int | IOBase | None.
• Used cast() only where mypy requires it, removed unnecessary cast().
• Removed unnecessary #type: ignore comments.

🔧 Implementation Notes

• Annotated self.log_output as Optional[Union[int, IOBase]].
• Alternative consideration was to simply use the annotation that the parameter log_output uses but that also includes str which the instance variable will never be str.
• added cast() on self.log_output = log_output because parameter log_output is annotated with IO[Any] instead of IOBase.

💡 Additional Considerations

• No tests are needed I already tested with mypy and ruff check
• This is my first PR if more changes are needed please let me know.

🔄 Types of changes

• Cleanup (formatting, renaming)

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PR Type

Other

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Description

• Fix type annotation errors in service.py

• Remove unnecessary type ignore comments

• Add proper type annotation for log_output instance variable

• Clean up cast() usage where not needed

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Diagram Walkthrough

flowchart LR
  A["Type Annotation Issues"] --> B["Add log_output Type Annotation"]
  B --> C["Remove Unnecessary Casts"]
  C --> D["Remove Type Ignore Comments"]
  D --> E["Clean Python Code"]

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File Walkthrough

	Relevant files
Miscellaneous	service.py Fix type annotations and remove unnecessary casts                py/selenium/webdriver/common/service.py Added explicit type annotation for log_output instance variable Removed unnecessary cast() calls in conditional branches Removed # type: ignore comments for Windows subprocess attributes Added single cast() where mypy requires it for type compatibility +7/-6

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[CLAassistant]

All committers have signed the CLA.

[qodo-merge-pro]

PR Reviewer Guide 🔍

Here are some key observations to aid the review process:

⏱️ Estimated effort to review: 2 🔵🔵⚪⚪⚪

🧪 No relevant tests

🔒 No security concerns identified

⚡ Recommended focus areas for review Type Narrowing Ensure the declared type of self.log_output matches all assigned values and downstream usage. It is annotated as Optional[Union[int, IOBase]], but assignments include None, subprocess.DEVNULL (int), IOBase from open(), and cast(Union[int, IOBase], log_output). Validate that any code consuming self.log_output handles all three cases correctly, especially when None represents STDOUT. self.log_output: Optional[Union[int, IOBase]] if isinstance(log_output, str): self.log_output = cast(IOBase, open(log_output, "a+", encoding="utf-8")) elif log_output == subprocess.STDOUT: self.log_output = None elif log_output is None or log_output == subprocess.DEVNULL: self.log_output = subprocess.DEVNULL else: self.log_output = cast(Union[int, IOBase],log_output) Resource Handling Opening a file when log_output is a string creates an IO handle; verify it is properly closed later (or managed contextually) to avoid file descriptor leaks, especially after changing types/casts that might affect lifecycle management assumptions. if isinstance(log_output, str): self.log_output = cast(IOBase, open(log_output, "a+", encoding="utf-8")) elif log_output == subprocess.STDOUT:

[qodo-merge-pro]

PR Code Suggestions ✨

Explore these optional code suggestions:

Category	Suggestion	Impact
Possible issue	Handle log file open failures Wrap file opening in a try/except to prevent crashes when the log file path is invalid or not writable. Fall back to subprocess.DEVNULL or None to keep the service start resilient. py/selenium/webdriver/common/service.py [61-62] if isinstance(log_output, str): - self.log_output = cast(IOBase, open(log_output, "a+", encoding="utf-8")) + try: + self.log_output = cast(IOBase, open(log_output, "a+", encoding="utf-8")) + except OSError: + self.log_output = subprocess.DEVNULL Apply / Chat Suggestion importance[1-10]: 7 __ Why: This suggestion correctly identifies a potential OSError when opening the log file, and the proposed try/except block makes the service initialization more resilient by preventing a crash.	Medium
General	✅ Ensure attribute is always initialized Suggestion Impact: The commit applied the formatting fix by adding a space after the comma in the cast call. It did not add the default initialization to None. code diff: - self.log_output = cast(Union[int, IOBase],log_output) + self.log_output = cast(Union[int, IOBase], log_output) Initialize self.log_output with a default to avoid potential mypy "possibly uninitialized" errors when new branches are added. Also fix minor formatting for readability. This keeps the attribute always defined and improves maintainability. py/selenium/webdriver/common/service.py [60-68] -self.log_output: Optional[Union[int, IOBase]] +self.log_output: Optional[Union[int, IOBase]] = None if isinstance(log_output, str): self.log_output = cast(IOBase, open(log_output, "a+", encoding="utf-8")) elif log_output == subprocess.STDOUT: self.log_output = None elif log_output is None or log_output == subprocess.DEVNULL: self.log_output = subprocess.DEVNULL else: - self.log_output = cast(Union[int, IOBase],log_output) + self.log_output = cast(Union[int, IOBase], log_output) [Suggestion processed] Suggestion importance[1-10]: 3 __ Why: The suggestion to initialize self.log_output at declaration is good practice for robustness and readability, although the existing if/elif/else structure already ensures it is always assigned a value.	Low
Update

[cgoldberg]

It's probably because I am using windows so mypy recognises the 'type' of this windows specific code on my end.

This is exactly the issue. We are using platform.system() for detecting Windows, but mypy doesn't respect that:

https://mypy.readthedocs.io/en/stable/common_issues.html#python-version-and-system-platform-checks

I wonder if we should change our platform detection across the entire codebase to use sys.platform instead? I thought platform.system() was the newer/better way, but it's causing issues here.

I don't really care if we leave the comments in this PR (we're going to get an error on one platform or the other either way). I'll open a new issue to investigate switching to sys.platform to avoid this.

[navin772]

LGTM! We can take care of windows error in the other issue created. Currently, mypy on CI runs on Ubuntu so it should not raise any type errors.