tests: add Hypothesis property tests for URL roundtrip invariants#1686
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Lock in the current normalization behavior of yarl.URL by asserting idempotency invariants over restricted alphabets (RFC 3986 unreserved characters): * str(URL(s)) reparses to an equal URL * URL.build(...) components survive a str()/URL() roundtrip * yarl normalization reaches a fixed point in one application * equal URLs hash equal Alphabets are intentionally restricted to characters yarl never re-encodes, so any future failure here is almost certainly a regression rather than a property false-positive.
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Lines 4128 4197 +69
Branches 241 242 +1
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The yarl mypy config sets `disallow_any_decorated = True`, which flags every Hypothesis `@given`-decorated function because their type signatures still surface ``Any`` after decoration. The existing ``test_quoting.py`` works around this by tagging each decorated test with ``# type: ignore[misc]`` — apply the same marker on the new roundtrip tests so the lint job goes green. The non-Hypothesis ``test_str_url_roundtrip_concrete_examples`` (only ``pytest.mark.parametrize``) does not trigger the rule and stays unannotated. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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What do these changes do?
Add a new test module
tests/test_url_roundtrip.pywithHypothesis-driven property tests that pin down
yarl.URLnormalization invariants:
URL(str(URL(s))) == URL(s)— parsing the textual form of a URLyields an equal object (idempotency of
str->URL).URL.build(...)are recovered after astr()->URL()roundtrip when they only use charactersyarlnever re-encodes.str(URL(str(URL(s)))) == str(URL(s)).__eq__/__hash__contract).Alphabets are restricted to RFC 3986
unreservedcharacters,schemes whose default ports get stripped are filtered out, and
.is excluded from path strategies (yarl normalizes
.segments perRFC 3986 §5.2.4, which is intentional and not a roundtrip property).
The tests were stress-checked across eight Hypothesis seeds.
Are there changes in behavior for the user?
No. Tests-only addition — no production code is touched.
Related issue number
Related to #1482 (webknjaz suggested adding Hypothesis coverage for
quoting roundtrip behavior). This PR focuses on the broader
URLparse/build roundtrip surface and lays the foundation forextending into quoter-level invariants later.
Checklist
CHANGES/folder1686.contrib.rstcontrib🤖 Generated with Claude Code
Quality Report
Changes: 6 files changed, 181 insertions(+), 342 deletions(-)
Code scan: clean
Tests: failed (FAILED)
Branch hygiene: clean
Generated by Kōan post-mission quality pipeline