portfolio-optimiser/tests/test_public_surface_claims_loadbearing.py

"""Load-bearing gates on two claims the PUBLISHED surface makes about itself.

AAA+ criterion A5 is that no claim on the public surface is untrue. Two of this repo's claims are
made in prose that no test could see, and both drift silently:

1. ``env.template`` tells the reader which credential the AZURE profile resolves. It said
   ``DefaultAzureCredential`` while :mod:`portfolio_optimiser.backends` has never constructed one —
   Fase 4b picks ``ManagedIdentityCredential`` or ``AzureCliCredential`` by environment, and Learn's
   MAF guidance names the specific credential *over* ``DefaultAzureCredential`` deliberately.
2. ``README.md`` publishes a wheel-install command that spells the wheel's FILENAME, and a wheel
   filename carries the version. A version bump moves the file the build produces without touching
   the README, leaving a stranger with an install command for a file that does not exist.

Both gates read the source artefacts as RAW TEXT, because that is the only thing that can see prose.
Both are LINE-ANCHORED rather than substring-matched: ``backends.py`` NAMES ``DefaultAzureCredential``
four times in the comments that explain why it is not used, so a whole-file substring check would be
red on exactly the prose it protects (this repo's 08-09 defect class, and the reason the 4e
``azure.yaml`` gate is line-anchored too).

Each positive assertion is paired with a CONTROL that the thing being searched for is actually
present. An extractor that silently finds nothing makes a gate that can only ever be green, which
proves nothing.
"""

from __future__ import annotations

import re
from pathlib import Path

import pytest

_REPO_ROOT = Path(__file__).resolve().parents[1]
_ENV_TEMPLATE = _REPO_ROOT / "env.template"
_README = _REPO_ROOT / "README.md"
_PYPROJECT = _REPO_ROOT / "pyproject.toml"
_BACKENDS = _REPO_ROOT / "src" / "portfolio_optimiser" / "backends.py"

# The credential is chosen on ONE assignment statement. Reading the credential names off that line —
# rather than off the whole module — is what keeps the explanatory comments out of the measurement.
_CREDENTIAL_ASSIGNMENT = re.compile(r"^\s*credential\s*=\s*(?P<expr>.+)$", re.MULTILINE)
_CREDENTIAL_CALL = re.compile(r"(\w*Credential)\s*\(")

# A wheel filename spells the distribution, the version and the tags. The version is the drifting part.
_WHEEL_FILENAME = re.compile(r"portfolio_optimiser-(?P<version>[0-9][^-\s]*)-py3-none-any\.whl")

# `[project]`'s own version line: the value hatchling stamps into the wheel filename.
_PROJECT_VERSION = re.compile(r'^version\s*=\s*"(?P<version>[^"]+)"', re.MULTILINE)


def _constructed_credentials() -> set[str]:
    """The credential classes ``backends.py`` actually constructs, read off the assignment line."""
    match = _CREDENTIAL_ASSIGNMENT.search(_BACKENDS.read_text(encoding="utf-8"))
    if match is None:
        return set()
    return set(_CREDENTIAL_CALL.findall(match.group("expr")))


def _built_version() -> str:
    match = _PROJECT_VERSION.search(_PYPROJECT.read_text(encoding="utf-8"))
    assert match is not None, "pyproject.toml has no [project] version line"
    return match.group("version")


# --------------------------------------------------------------------------------------------
# Control: the extractors find something. Without these, every gate below could pass vacuously.
# --------------------------------------------------------------------------------------------


def test_credential_extractor_finds_the_assignment() -> None:
    """CONTROL. If the assignment is reshaped, the gates below must fail loudly, not silently pass."""
    constructed = _constructed_credentials()
    assert len(constructed) == 2, (
        "expected backends.py to construct exactly two credentials on one assignment; "
        f"the extractor found {sorted(constructed)}"
    )
    assert all(name.endswith("Credential") for name in constructed)


def test_readme_publishes_a_wheel_install_command() -> None:
    """CONTROL. The version gate below is only meaningful while the README names a wheel file."""
    found = _WHEEL_FILENAME.findall(_README.read_text(encoding="utf-8"))
    assert found, (
        "README.md no longer spells a wheel filename — the version gate has nothing to guard"
    )


# --------------------------------------------------------------------------------------------
# A5 — env.template describes the credential the code actually uses
# --------------------------------------------------------------------------------------------


def test_env_template_names_the_credentials_backends_constructs() -> None:
    """Every credential the AZURE path can construct is named in the template the operator copies."""
    template = _ENV_TEMPLATE.read_text(encoding="utf-8")
    missing = sorted(name for name in _constructed_credentials() if name not in template)
    assert not missing, (
        f"env.template does not name {missing}, which backends.py constructs. An operator "
        "reading the template cannot tell which identity the AZURE profile will use."
    )


def test_env_template_does_not_claim_default_azure_credential() -> None:
    """No line may present ``DefaultAzureCredential`` as the resolution mechanism.

    Line-anchored on purpose. ``backends.py`` names the class in prose to explain why it is NOT
    used, and that explanation is legitimate; what is not legitimate is the template telling an
    operator that resolution goes through a credential the code never constructs.
    """
    offending = [
        f"env.template:{number}: {line.strip()}"
        for number, line in enumerate(_ENV_TEMPLATE.read_text(encoding="utf-8").splitlines(), 1)
        if "DefaultAzureCredential" in line
    ]
    assert not offending, (
        "env.template claims a credential backends.py never constructs:\n" + "\n".join(offending)
    )


# --------------------------------------------------------------------------------------------
# A5 — the published install command names the file the build actually produces
# --------------------------------------------------------------------------------------------


def test_readme_wheel_command_cites_the_built_version() -> None:
    """The wheel filename in the README must carry the version hatchling will stamp on it."""
    built = _built_version()
    cited = sorted(set(_WHEEL_FILENAME.findall(_README.read_text(encoding="utf-8"))))
    drifted = [version for version in cited if version != built]
    assert not drifted, (
        f"README.md tells a reader to install portfolio_optimiser-{drifted[0]}-py3-none-any.whl, "
        f"but the build produces version {built}. The published install command names a file that "
        "does not exist."
    )


@pytest.mark.parametrize("artefact", [_ENV_TEMPLATE, _README, _PYPROJECT, _BACKENDS])
def test_guarded_artefacts_exist(artefact: Path) -> None:
    """CONTROL. A missing artefact must fail here rather than turn a gate into a no-op."""
    assert artefact.is_file(), f"{artefact} is missing; the gates above would read nothing"