perf: fast path for simple versions (intermediate commit 61967cca)

Ultra's plan · 5 attacks

Nemotron 3 Ultra read the diff and named the assumptions the change makes. Nothing here is trusted: each attack only counts through the counterexamples below.

1. A1The fast‑path guard assumes that a version lacking the indicator characters contains only ASCII digits and dots, so it splits on '.' and feeds each piece to int().

   base: The old __init__ falls through to the full regex (self._regex.fullmatch). The pattern does not allow whitespace between the dot and the digits, so the match fails and InvalidVersion is raised.; head: The fast‑path executes: version.strip().split('.') yields pieces like '1 ' and '2'; int() accepts the surrounding whitespace, so a Version object is created with release=(1, 2).

   Inputs: versions with spaces adjacent to the dot separator · e.g. Version("1 .2"), Version("1. 2") · Lightning strategies: 3/4 valid, 2 hits

2. A2The fast‑path guard assumes that any string lacking the indicator characters consists only of ASCII digits and dots, so int() will only ever see ASCII digits.

   base: `Version("１.２")` falls through to the regex path; `VERSION_PATTERN` uses `[0-9]` which matches only ASCII digits, so the fullmatch fails and `InvalidVersion` is raised.; head: The fast‑path is taken, `version.strip().split(".")` yields `["１", "２"]`; `int()` accepts Unicode decimal digits, producing `(1, 2)`. A `Version` instance is created with `release=(1, 2)` and no exception.

   Inputs: PEP‑440‑like release segment written with non‑ASCII decimal digits · e.g. Version("１.２") · Lightning strategies: 3/4 valid, 1 hits

3. A3The fast‑path assumes `int()` only accepts ASCII decimal digits; it treats any string without the indicator characters as a simple numeric version.

   base: The regex `VERSION_PATTERN` only matches ASCII `[0-9]` in the release segment, so `Version("١.٢.٣")` raises `InvalidVersion`.; head: The fast‑path runs `version.strip().split('.')` and `map(int, …)`. `int()` accepts Unicode decimal digits, so the version is accepted and normalized to `(1, 2, 3)`.

   Inputs: non‑ASCII decimal digits (Arabic‑Indic) · e.g. Version("١.٢.٣") · Lightning strategies: 3/4 valid, 2 hits

4. A4The fast‑path guard assumes that a version without indicator characters consists solely of ASCII decimal digits, but int() also accepts any Unicode decimal digit.

   base: The regex uses [0-9] for the release segment, which matches only ASCII digits; the fullmatch fails and InvalidVersion is raised.; head: The fast‑path splits on '.' and calls int() on each segment; int() accepts full‑width digits (e.g. U+FF11), so a Version object is created with release=(1, 2).

   Inputs: versions written with non‑ASCII decimal digits · e.g. Version("１.２"), Version("１２３.４５６") · Lightning strategies: 2/4 valid, 0 hits

5. A5The fast‑path guard assumes that a string without indicator characters contains no whitespace inside the release segment.

   base: Regex `\s*` only permits leading/trailing whitespace; the pattern for `release` (`[0-9]+(?:\.[0-9]+)*`) does not allow a space between a digit and a dot, so `fullmatch` fails and `InvalidVersion` is raised.; head: Fast‑path executes; `strip()` removes only leading/trailing whitespace, `split(".")` gives `["1 ", "2"]`; `int("1 ")` succeeds (int ignores surrounding whitespace), producing `release=(1, 2)`. A `Version` instance is returned.

   Inputs: Release segment with ASCII whitespace around the dot separator · e.g. Version("1 .2"), Version("1. 2") · Lightning strategies: 3/4 valid, 1 hits

Counterexamples · 5 groups of 6 classes: 4 likely bug, 2 intended

def test_p2_outcome_0():
    """Breakwater P2: base behaviour pinned (found by differential testing; label: likely-bug)."""
    import pytest
    from packaging.version import InvalidVersion, Version
    with pytest.raises(InvalidVersion) as excinfo:
        Version('0 .0')
    assert type(excinfo.value) is InvalidVersion  # exact type: a subclass would be a behaviour change

uv run breakwater probe --repo https://github.com/pypa/packaging --base 59f183fe90da --head 61967cca278d --target packaging.version:Version --backend contree --input "0 .0"

def test_p2_outcome_2():
    """Breakwater P2: base behaviour pinned (found by differential testing; label: likely-bug)."""
    import pytest
    from packaging.version import InvalidVersion, Version
    with pytest.raises(InvalidVersion) as excinfo:
        Version('٠')
    assert type(excinfo.value) is InvalidVersion  # exact type: a subclass would be a behaviour change

uv run breakwater probe --repo https://github.com/pypa/packaging --base 59f183fe90da --head 61967cca278d --target packaging.version:Version --backend contree --input "٠"

def test_p2_outcome_1():
    """Breakwater P2: base behaviour pinned (found by differential testing; label: likely-bug)."""
    import pytest
    from packaging.version import Version
    with pytest.raises(TypeError) as excinfo:
        Version(['１'])
    assert type(excinfo.value) is TypeError  # exact type: a subclass would be a behaviour change

Regression tests

4 of 6 classes have a generated pytest that passed on base and failed on head in the sandbox.

Download test_regressions.py

Performance · Version

Worst family with mostly valid inputs: 2.74× the instructions of base (Trailing numeric sub-label added).

Receipt