Modernize ConftestImportFailure to use the exception chain - #14943
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Modernize ConftestImportFailure to use the exception chain#14943RonnyPfannschmidt wants to merge 2 commits into
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A plugin failing to load during startup escaped `_main` as an unhandled exception: Python printed a raw traceback and exited 1, which is indistinguishable from EXIT_TESTSFAILED. Meanwhile a conftest.py failing to import already returned EXIT_USAGEERROR, which is the inconsistency pytest-dev#993 was filed about. Split the failure into the two things it can actually mean: - the plugin cannot be found at all -- pytest was pointed at something which is not there, so this is a usage error (exit 4), matching what conftest.py import failures already do. - the plugin was found but raised while importing -- including a missing transitive dependency and a broken pytest11 entry point -- which is a defect in the plugin rather than a misuse of pytest, so it is reported as an internal error (exit 3). The plugin traceback is preserved in both the report and the exception chain (PluginImportFailure is always raised `from` the original error); losing it was the main objection to the earlier attempt in pytest-dev#7290. Side effects: - pytest.main() now returns these exit codes instead of propagating the exception to its caller, matching its documented contract. - a bare `raise ImportError` in a plugin no longer crashes pytest's own internals with `IndexError: tuple index out of range` from `e.args[0]`. conftest.py import failures are deliberately left alone and keep returning exit 4. Co-Authored-By: Claude Opus 5 <ai@anthropic.com> Co-Authored-By: Claude Fable 5 <ai@anthropic.com> Co-Authored-By: Claude Code <ai@anthropic.com>
Give ConftestImportFailure the same shape PluginImportFailure just got: a bare Exception subclass whose argument is the conftest path, with the original error carried by `raise ... from` on __cause__ instead of a hand-rolled `cause` attribute duplicating it. The custom __init__ and __str__ go away; str(e) is the path, which is exactly what the two message consumers want. The `cause` attribute dates to 8.0 (e1074f9), which replaced the old excinfo triplet without deprecation; the class is private to _pytest.config and a code search finds no external consumers, only vendored copies of pytest itself. No user-visible output changes. Co-Authored-By: Claude Fable 5 <ai@anthropic.com> Co-Authored-By: Claude Code <ai@anthropic.com>
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Stacked on #14824 — review only the last commit; the first is that PR.
Gives
ConftestImportFailurethe same shapePluginImportFailuregot in #14824: a bareExceptionsubclass whose argument is the conftest path, with the original error carried byraise ... fromon__cause__instead of a hand-rolledcauseattribute duplicating the chain. The custom__init__and__str__go away;str(e)is the path, which is exactly what both message consumers want.Why this is safe:
causeattribute is young — introduced in 8.0 (e1074f9) replacing the oldexcinfotriplet, without deprecation;_pytest.config(not exported aspytest.*), and a GitHub code search finds no external importers, only vendored copies of pytest itself;print_conftest_import_error, the--help/--versiongrace path,Node._repr_failure_pyunwrapping,--pdbpost-mortem unwrapping,_main) are updated in this PR.No user-visible output changes.
🤖 Written by Claude Code (Claude Fable 5); reviewed and submitted by @RonnyPfannschmidt.