UsageError("unmanaged values can not be compared with snapshots") when using -k flag #355

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Description

Related Issue(s)

Checklist

• I have tested my changes thoroughly (you can download the test coverage with hatch run cov:github).
• I have added/updated relevant documentation.
• I have added tests for new functionality (if applicable).
• I have reviewed my own code for errors.
• I have added a changelog entry with hatch run changelog:entry
• I used semantic commits (feat: will cause a major and fix: a minor version bump)
• You can squash you commits, otherwise they will be squashed during merge

[MRigal]

To get even more, at least for Python 3.11+ (probably 80-90% of the users by now), you could use https://docs.python.org/3/library/exceptions.html#lib-exception-groups to collect even more details :-)

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but ExceptionGroup is derived from Exception, which means that this code catches already ExceptionGroup. Or am I missing something here?

[Copilot]

Pull request overview

This PR improves error reporting when collecting snapshot changes (during show_report()), and adds tests to verify the new error output. It also extends the Example.run_inline() helper to support injecting additional context managers (used by the new tests).

Changes:

• Wrap snapshot change collection in SnapshotSession.show_report() to raise a RuntimeError that includes snapshot expression + file/line.
• Extend Example.run_inline() to accept extra context_managers for test-time patching.
• Refactor/add tests to validate string-update output and the new change-collection error reporting (including Windows path normalization).

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/utils.py	Adds a reusable path_transform to normalize Windows path separators in snapshots.
tests/test_string.py	Refactors string snapshot tests and introduces a helper fixture to reduce duplication.
tests/test_change_collection_error.py	Adds coverage for the new error message when _changes() raises during report generation.
src/inline_snapshot/testing/_example.py	Adds support for injecting context managers into inline example runs; adjusts exception handling/reporting behavior.
src/inline_snapshot/_types.py	Adds typing for _expr on snapshot references.
src/inline_snapshot/_snapshot_session.py	Adds error-wrapping around snapshot._changes() to improve diagnostics (file/line + snapshot repr).
src/inline_snapshot/_snapshot/undecided_value.py	Removes change-generation logic for undecided values (now yields no changes by default).
src/inline_snapshot/_inline_snapshot.py	Adds __repr__ for SnapshotReference and tightens AST typing with cast().

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