FabledGrimoire/tests/test_contract_around_the_change.py

"""You altered the shape of something — here is everything that reads it.

WHY THIS EXISTS

The commonest miss is acting on the thing in hand without reading the contract
around it: "widening a tuple is an interface change to every unpack site, and
the compiler will not tell you". Knowing that in words does not stop it — text
delivered at the moment of acting is too weak a carrier for a reflex that has
to change what the act IS. This looks it up instead.

Layer parity one scope down: its checks are between layers ("every parameter the
caller sends is read by the handler under the same name"), and the same
question exists between a definition and its callers.

THREE KINDS OF EXPOSED NAME, because a contract breaks three ways that look
nothing alike in source:

    sym   what is defined              a rename or a removal
    arg   its parameter names          arity and order
    key   quoted keys of dict literals the shape of what it RETURNS

The third is the one a signature-watcher misses: a function gains one dict
key, three callers read that dict inside a fail-open `except`, every one
silently becomes a no-op, and tests go red at once with nothing pointing at
the cause. No signature changed.

WHAT IS PINNED: which edits speak and which stay silent, and that both gates
are load-bearing. NOT pinned: the wording, which is prose.

A FIXTURE REPO, NEVER THIS ONE. Asserting against Scribe's own files would
make the test a description of today's tree, failing the next time someone
renames something.
"""
import subprocess
from pathlib import Path

import pytest

from tests.helpers import need_tools

DEFS = Path(__file__).resolve().parents[1] / "plugin" / "hooks" / "scribe_defs.sh"
HOOK = Path(__file__).resolve().parents[1] / "plugin" / "hooks" / "scribe_prior_art.sh"


def run(script: str) -> str:
    need_tools("bash", "awk", "git", "grep", "sed")
    r = subprocess.run(
        ["bash", "-c", f'set -uo pipefail\n. "{DEFS}"\n{script}'],
        capture_output=True, text=True,
    )
    assert r.returncode == 0, f"exit {r.returncode}: {r.stderr}"
    return r.stdout


@pytest.fixture()
def repo(tmp_path):
    """A small git repo: a definition with a reader, and one without."""
    need_tools("git")
    # `other` lives in lib.py BESIDE widget, and nothing references it. That
    # placement is the point of the no-readers case: putting it in its own
    # file would leave that file as its reader, since only the file being
    # edited is excluded — which is how the first version of this fixture
    # quietly tested the opposite of what it claimed.
    (tmp_path / "lib.py").write_text(
        "def widget(size, colour):\n"
        '    return {"size": size, "colour": colour}\n\n'
        "def other():\n    return 1\n"
    )
    (tmp_path / "caller.py").write_text(
        "from lib import widget\n\n"
        "def render():\n"
        '    return widget(1, "red")["size"]\n'
    )
    (tmp_path / "unrelated.py").write_text("def gizmo():\n    return 2\n")
    subprocess.run(["git", "init", "-q"], cwd=tmp_path, check=True)
    subprocess.run(["git", "add", "-A"], cwd=tmp_path, check=True)
    return tmp_path


def q(text: str) -> str:
    """A multi-line blob as one bash word, newlines intact.

    ANSI-C quoting (`$'...'`) and NOT Python's `repr`, which is what the first
    version of this file used. Inside ordinary single quotes bash leaves `\\n`
    as two characters and `printf %s` does not interpret it either, so every
    fixture arrived as a SINGLE line. The extractor is line-oriented, so the
    cases still passed — the test would have gone green while exercising input
    no editor could produce. Escaping is explicit rather than delegated to
    `repr`, whose quote character depends on the content.
    """
    esc = (text.replace("\\", "\\\\").replace("'", "\\'")
               .replace("\n", "\\n").replace("\t", "\\t"))
    return "$'" + esc + "'"


def block(repo, subject, old, new, ledger="") -> str:
    return run(
        f'scribe_contract_block "{repo}" "lib.py" "{subject}" '
        f'{q(old)} {q(new)} "{ledger}"'
    )


# ── scribe_exposed: the three kinds ───────────────────────────────────────

def exposed(text: str) -> set[str]:
    out = run(f'printf %s {q(text)} | scribe_exposed')
    return {ln for ln in out.split("\n") if ln.strip()}


def test_a_definitions_name_is_exposed():
    assert "sym\twidget" in exposed("def widget(size):\n    pass\n")


def test_parameter_names_are_exposed():
    got = exposed("def widget(size, colour):\n    pass\n")
    assert "arg\tsize" in got and "arg\tcolour" in got


def test_self_and_cls_are_not_part_of_the_contract():
    """Nothing a caller passes, so naming them would report a change on every
    method that gains a keyword argument."""
    got = exposed("def method(self, size):\n    pass\n")
    assert "arg\tself" not in got
    assert "arg\tsize" in got


def test_a_type_annotation_and_a_default_are_stripped_from_a_parameter():
    got = exposed('def f(user_id: int, days: int = 30, *, flag=False):\n    pass\n')
    assert {"arg\tuser_id", "arg\tdays", "arg\tflag"} <= got


def test_a_quoted_dict_key_is_exposed():
    """THE CASE A SIGNATURE-WATCHER MISSES, and the one that produced this
    step — see the module docstring."""
    assert 'key\tcheckpoint_threshold' in exposed('    "checkpoint_threshold": floor,\n')


def test_reading_a_dict_key_does_not_count_as_defining_one():
    """Anchored on the writing position (`"k":`), so `cfg["k"]` says nothing.
    Without this every consumer of a config would report a contract change
    the moment it read one."""
    assert exposed('x = cfg["tool_rule_threshold"]\ny = d.get("other")\n') == set()


def test_a_dunder_is_never_exposed():
    """Every class defines __init__, so it would be a guaranteed false
    positive on every class edit — and noise is what teaches a reader to skip
    the block."""
    assert "sym\t__init__" not in exposed("    def __init__(self, x):\n        pass\n")


# ── The check: what speaks, and what stays quiet ──────────────────────────

def test_a_gained_dict_key_names_the_files_that_read_it(repo):
    out = block(
        repo, "widget",
        'def widget(size, colour):\n    return {"size": size}\n',
        'def widget(size, colour):\n    return {"size": size, "weight": 1}\n',
    )
    assert "widget" in out
    assert "gained" in out and "weight" in out
    assert "caller.py" in out
    assert "unrelated.py" not in out, "only files that reference the subject"


def test_a_gained_parameter_names_the_files_that_read_it(repo):
    out = block(repo, "widget", "def widget(size):\n", "def widget(size, colour):\n")
    assert "colour" in out and "caller.py" in out


def test_a_rename_reports_both_halves(repo):
    out = block(repo, "widget", "def widget(size):\n", "def gadget(size):\n")
    assert "lost" in out and "widget" in out
    assert "gained" in out and "gadget" in out


def test_a_body_only_edit_says_nothing(repo):
    """THE GATE THAT DECIDES WHETHER THIS IS USABLE. Most edits are bodies; a
    check that spoke on all of them would be skipped by the third turn."""
    out = block(
        repo, "widget",
        "def widget(size, colour):\n    total = size\n    return total\n",
        "def widget(size, colour):\n    total = size + 1\n    return total\n",
    )
    assert out.strip() == ""


def test_a_definition_nothing_references_says_nothing(repo):
    """THE SECOND GATE, and it is not redundant. A shape change is necessary
    but not sufficient — a definition with no readers has no contract to
    break, and on any real repo this is what keeps the check quiet."""
    out = block(repo, "other", "def other():\n", "def other(x):\n")
    assert out.strip() == ""


def test_the_same_subject_is_named_once_per_session(repo, tmp_path):
    """Getting a change right takes several passes over the same definition,
    and re-asking the same contract question at each one punishes exactly the
    rhythm that gets it right."""
    ledger = tmp_path / "sid.contract.ids"
    first = block(repo, "widget", "def widget(size):\n",
                  "def widget(size, colour):\n", ledger=str(ledger))
    assert first.strip()
    second = block(repo, "widget", "def widget(size):\n",
                   "def widget(size, colour):\n", ledger=str(ledger))
    assert second.strip() == ""


def test_a_missing_old_text_says_nothing(repo):
    """A Write that creates a file has no `before`, so there is no contract to
    have changed. Silence, never a report against an empty string."""
    assert block(repo, "widget", "", "def widget(size, colour):\n").strip() == ""


# ── The hook that carries it ──────────────────────────────────────────────

def test_the_write_hook_still_cannot_stop_a_write():
    """THE RECORDED DECISION THIS ARM MUST NOT ERODE. The operator's position
    is that a recall aid may not stand in the way of a write, and this arm is
    a nudge like the others — it names files, it does not gate. Asserted here
    as well as in test_write_path_trigger.py because this is the change most
    likely to tempt someone into making it a gate: it reports something that
    may already be broken.
    """
    code = [ln for ln in HOOK.read_text().splitlines()
            if not ln.lstrip().startswith("#")]
    assert not any("permissionDecision" in ln for ln in code)
    assert not any("scribe_json_deny" in ln for ln in code)


def test_the_hook_asks_the_contract_question_first():
    """Order is the strength of the claim: this arm says something may already
    be BROKEN, the local arm says a copy exists, the recorded arms say
    something resembles this. A reader who reads one line should read that
    one."""
    code = [ln for ln in HOOK.read_text().splitlines()
            if not ln.lstrip().startswith("#")]
    combined = next(i for i, ln in enumerate(code) if ln.startswith("combined="))
    assert "contract_context" in code[combined]


def test_the_hook_is_still_shell_valid():
    need_tools("bash")
    subprocess.run(["bash", "-n", str(HOOK)], check=True)
    subprocess.run(["bash", "-n", str(DEFS)], check=True)