fix: close ZipFile in _prefetch_metadata with context manager

[dimbleby]

ZipFile opened in _prefetch_metadata was never closed. If an UnsupportedWheelError was raised, the handle leaked. Changed bare ZipFile() assignment to a with statement for proper cleanup.

github and whitespace do not make a pretty diff, nothing has changed in the main body of what happens

Summary by Sourcery

Ensure wheel metadata prefetching closes ZipFile handles even when errors occur.

Bug Fixes:

• Prevent ZipFile handle leaks in _prefetch_metadata by using a context manager for opening wheels.

Tests:

• Add a regression test verifying that ZipFile is closed when _prefetch_metadata raises an error.

[sourcery-ai]

Reviewer's Guide

Refactors LazyWheelOverHTTP._prefetch_metadata to open ZipFile with a context manager so it is always closed, and adds a regression test to assert the ZipFile is closed even when metadata discovery fails with an error.

Sequence diagram for _prefetch_metadata with ZipFile context manager

sequenceDiagram
    participant caller as LazyWheelOverHTTP_caller
    participant wheel as LazyWheelOverHTTP
    participant zlib as ZipFile

    caller->>wheel: _prefetch_metadata(name)
    activate wheel
    wheel->>zlib: __enter__()
    activate zlib

    loop iterate_zip_entries
        wheel->>zlib: infolist()
        zlib-->>wheel: list[ZipInfo]
        wheel->>wheel: search for metadata filename
    end

    alt metadata_found
        wheel->>wheel: determine start and end offsets
        wheel->>wheel: _ensure_downloaded(start, end)
        wheel-->>caller: return metadata_path
    else metadata_not_found
        wheel->>wheel: raise UnsupportedWheelError
    end

    zlib-->>wheel: __exit__()
    deactivate zlib
    deactivate wheel

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Class diagram for LazyWheelOverHTTP and supporting types in _prefetch_metadata

classDiagram
    class LazyWheelOverHTTP {
        +str name
        +Pattern _metadata_regex
        +str _prefetch_metadata(str name)
        +_ensure_downloaded(int start, int end)
    }

    class ZipFile {
        +infolist() list~ZipInfo~
        +start_dir int
        +close() void
    }

    class ZipInfo {
        +str filename
        +int header_offset
    }

    class UnsupportedWheelError {
        +UnsupportedWheelError(str message)
    }

    LazyWheelOverHTTP ..> ZipFile : uses
    LazyWheelOverHTTP ..> ZipInfo : iterates
    LazyWheelOverHTTP ..> UnsupportedWheelError : raises

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File-Level Changes

Change	Details	Files
Ensure ZipFile opened in _prefetch_metadata is always closed via a context manager.	Wrap ZipFile(self) usage in a with statement and indent the metadata scanning logic into the context manager body Keep existing control flow for locating .dist-info/METADATA entries and computing start/end offsets unchanged aside from indentation Use zf.start_dir inside the context manager when computing the end offset for the last entry	src/poetry/inspection/lazy_wheel.py
Add regression test verifying ZipFile is closed on error during metadata prefetch.	Instantiate a LazyWheelOverHTTP object without running init and configure its _metadata_regex and _file.name manually Patch poetry.inspection.lazy_wheel.ZipFile to return a MagicMock ZipFile that yields only non-matching entries from infolist Assert that _prefetch_metadata raises an UnsupportedWheelError and that the mocked ZipFile.exit is called exactly once	tests/inspection/test_lazy_wheel.py

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[sourcery-ai]

Hey - I've found 1 issue, and left some high level feedback:

• In test_prefetch_metadata_closes_zipfile_on_error, consider asserting pytest.raises(UnsupportedWheelError, ...) instead of catching a generic Exception to keep the test focused on the expected failure mode.
• The new test heavily mocks ZipFile; you might simplify and make it more robust by constructing a small in-memory wheel/zip that lacks a matching .dist-info/METADATA entry instead of patching ZipFile and its methods.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `test_prefetch_metadata_closes_zipfile_on_error`, consider asserting `pytest.raises(UnsupportedWheelError, ...)` instead of catching a generic `Exception` to keep the test focused on the expected failure mode.
- The new test heavily mocks `ZipFile`; you might simplify and make it more robust by constructing a small in-memory wheel/zip that lacks a matching `.dist-info/METADATA` entry instead of patching `ZipFile` and its methods.

## Individual Comments

### Comment 1
<location path="tests/inspection/test_lazy_wheel.py" line_range="496-497" />
<code_context>
+    mock_zf.__exit__ = MagicMock(return_value=False)
+
+    with (
+        patch("poetry.inspection.lazy_wheel.ZipFile", return_value=mock_zf),
+        pytest.raises(Exception, match=r"no .* found for"),
+    ):
+        lazy._prefetch_metadata("test-pkg")
</code_context>
<issue_to_address>
**suggestion (testing):** Assert the specific `UnsupportedWheelError` instead of a generic `Exception`

This test is asserting that `_prefetch_metadata` raises `UnsupportedWheelError` when no matching `.dist-info/METADATA` is found, but `pytest.raises(Exception, ...)` is too broad and would still pass if a different exception were raised. Please import and assert the specific exception:

```python
from poetry.inspection.lazy_wheel import LazyWheelOverHTTP, UnsupportedWheelError
...
with (
    patch("poetry.inspection.lazy_wheel.ZipFile", return_value=mock_zf),
    pytest.raises(UnsupportedWheelError, match=r"no .* found for"),
):
    lazy._prefetch_metadata("test-pkg")
```

This keeps the test aligned with the intended contract and will fail if the exception type changes unexpectedly.

Suggested implementation:

```python
from poetry.inspection.lazy_wheel import LazyWheelOverHTTP, UnsupportedWheelError

```

```python
    with (
        patch("poetry.inspection.lazy_wheel.ZipFile", return_value=mock_zf),
        pytest.raises(UnsupportedWheelError, match=r"no .* found for"),
    ):
        lazy._prefetch_metadata("test-pkg")

```
</issue_to_address>

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