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autospec doesn't work with lazy-imported symbols #153888
Description
Bug report
Bug description:
unittest.mock.patch(target, autospec=True) reads unresolved lazy-import bindings directly from target.__dict__ and autospecs the LazyImportType proxy instead of the imported symbol.
from unittest.mock import patch
lazy from json import dumps
with patch("__main__.dumps", autospec=True) as mock_dumps:
mock_dumps({})On CPython main (9d231cbc937f as of now), this raises:
TypeError: 'NonCallableMagicMock' object is not callable
Resolving dumps before patching works. This also affects patch.object, spec=True, and spec_set=True.
A practical example is concurrent.futures.ThreadPoolExecutor, which now uses an explicit lazy import: existing tests such as this one patch it with autospec=True and encounter the same issue.
CPython versions tested on:
CPython main branch
Operating systems tested on:
Linux, macOS, Windows
Activity
Resolve lazy imports before using them as a mock spec
brittanyrey commentedon Sep 18, 2026
The linked PR has fallen stale for the last 2 months. With the 3.15 final cut coming up, I'm putting up a new PR which also addresses the open comments left on the original PR. #157768
gh-153888: Resolve lazy imports before using them as a mock spec (GH-…
[3.15] gh-153888: Resolve lazy imports before using them as a mock sp…
test: fix flaky autospec of lazy-imported logger on 3.15 (#1209)
Resolve a lazy import before unittest.mock specs it