ruff 0.15.22: Resolve Ruff configuration precedence across .ruff.toml, ruff.toml, pyproject.toml, and CLI flags with rule composition semantics

# Ruff Configuration Precedence & Rule Composition Notes

## Known Solution Search
`search_known_solution` returned a **MISS** for Python Ruff configuration precedence (returned unrelated sample `sha256:ea36c1c79c3a4263305e79d2403494634711a275d2fd41a2d8df834ac7e9101b` for Go `spf13/viper`).

## What a Model Would Have Written Instead
A model would assume that `ruff.toml` and `pyproject.toml` [tool.ruff] merge hierarchically when co-located, that subdirectories automatically inherit parent configurations without `extend`, and that CLI `--select` appends to config selections or respects config `ignore`.

## Failure Mode
Silently with a green build: misplaced configurations in `pyproject.toml` or parent directories are silently ignored without error, causing critical lint rules or file-specific ignores to be dropped unnoticed during CI.

{"case":{"caseId":"case:sha256:bb6e3d137e4308879589b84551863c9793f312236aeb36778f0f6362a5d8b242","constraints":{"runtime":"python"},"contract":["assert .ruff.toml shadows ruff.toml which shadows pyproject.toml in the same directory without merging","assert child directories do not inherit parent configuration without an explicit extend setting","assert CLI --select wipes both config select and extend-select whereas --extend-select is additive","assert CLI --select overrides configuration ignore rules for the selected code","assert extend-per-file-ignores merges per-file ignores while per-file-ignores replaces them"],"goal":"Resolve Ruff configuration precedence across .ruff.toml, ruff.toml, pyproject.toml, and CLI flags with rule composition semantics","kind":"HOW","packages":["pkg:pypi/ruff@0.15.22"],"schemaVersion":1,"symbols":["ruff.find_ruff_bin"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","ecosystem":"pypi","executionContext":"python","language":"python","os":"linux","packageManager":"pip","runtime":"python","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/ruff@0.15.22"],"schemaVersion":1,"symbols":["ruff.find_ruff_bin"],"verifierAdapter":"python@1"}

ruff==0.15.22

"""Ruff configuration precedence and rule composition suite."""

"""Helper utilities to invoke Ruff against isolated directory configurations."""

import json
import os
import subprocess
import ruff


def get_ruff_binary() -> str:
    """Resolve the path to the Ruff binary using ruff.find_ruff_bin()."""
    return os.fsdecode(ruff.find_ruff_bin())


def run_ruff_check(cwd: str, *extra_args: str) -> list[str]:
    """Execute ruff check in a directory and return sorted violation codes."""
    bin_path = get_ruff_binary()
    cmd = [bin_path, "check", "--output-format", "json", *extra_args]
    proc = subprocess.run(
        cmd,
        cwd=cwd,
        capture_output=True,
        text=True,
    )
    if proc.returncode not in (0, 1):
        raise RuntimeError(f"Ruff failed with code {proc.returncode}: {proc.stderr}")
    try:
        diagnostics = json.loads(proc.stdout) if proc.stdout.strip() else []
        return sorted([d["code"] for d in diagnostics])
    except json.JSONDecodeError as err:
        raise RuntimeError(f"Failed to parse JSON output: {proc.stdout}") from err

"""Contract proving Ruff configuration precedence and rule composition behavior."""

import os
import sys
import tempfile

sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
from src.precedence import run_ruff_check

# Sample file content that triggers both E401 (multiple imports on one line)
# and two F401 (unused imports: os and sys).
SAMPLE_CODE = "import os, sys\n"


def test_same_directory_file_precedence():
    """Assert .ruff.toml > ruff.toml > pyproject.toml and files do NOT merge."""
    with tempfile.TemporaryDirectory() as d:
        with open(os.path.join(d, "sample.py"), "w", encoding="utf-8") as f:
            f.write(SAMPLE_CODE)

        # 1a. ruff.toml overrides pyproject.toml [tool.ruff]
        with open(os.path.join(d, "pyproject.toml"), "w", encoding="utf-8") as f:
            f.write('[tool.ruff.lint]\nselect = ["F401"]\n')
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["E401"]\n')
        # Only E401 is selected; F401 from pyproject.toml is completely ignored
        assert run_ruff_check(d, "sample.py") == ["E401"]

        # 1b. .ruff.toml overrides ruff.toml
        with open(os.path.join(d, ".ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["F401"]\n')
        # .ruff.toml wins over ruff.toml
        assert run_ruff_check(d, "sample.py") == ["F401", "F401"]

        # 1c. Shadowing without merging: non-lint ruff.toml drops pyproject.toml rules
        os.remove(os.path.join(d, ".ruff.toml"))
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write("line-length = 100\n")
        # pyproject.toml has select = ["F401"], but ruff.toml shadows it completely.
        # Ruff falls back to default rule set (E4, E7, E9, F) producing E401 + F401*2.
        assert run_ruff_check(d, "sample.py") == ["E401", "F401", "F401"]


def test_directory_hierarchy_and_extend():
    """Assert child directory configs do NOT inherit parent configs without extend."""
    with tempfile.TemporaryDirectory() as d:
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["E401"]\n')

        sub = os.path.join(d, "pkg")
        os.makedirs(sub)
        with open(os.path.join(sub, "sample.py"), "w", encoding="utf-8") as f:
            f.write(SAMPLE_CODE)

        # 2a. Without extend, child ruff.toml does not inherit parent's select
        with open(os.path.join(sub, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write("line-length = 100\n")
        assert run_ruff_check(d, "pkg/sample.py") == ["E401", "F401", "F401"]

        # 2b. With extend = "../ruff.toml", child inherits parent's select = ["E401"]
        with open(os.path.join(sub, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('extend = "../ruff.toml"\nline-length = 100\n')
        assert run_ruff_check(d, "pkg/sample.py") == ["E401"]


def test_select_vs_extend_select_composition():
    """Assert CLI --select wipes config selections while --extend-select is additive."""
    with tempfile.TemporaryDirectory() as d:
        with open(os.path.join(d, "sample.py"), "w", encoding="utf-8") as f:
            f.write(SAMPLE_CODE)
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["F401"]\nextend-select = ["E401"]\n')

        # Baseline: config has both active
        assert run_ruff_check(d, "sample.py") == ["E401", "F401", "F401"]

        # CLI --select replaces BOTH select and extend-select from config
        assert run_ruff_check(d, "--select", "F401", "sample.py") == ["F401", "F401"]

        # CLI --extend-select adds to config
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["F401"]\n')
        assert run_ruff_check(d, "--extend-select", "E401", "sample.py") == ["E401", "F401", "F401"]


def test_cli_select_overrides_ignore():
    """Assert CLI --select re-enables rules explicitly disabled by config ignore."""
    with tempfile.TemporaryDirectory() as d:
        with open(os.path.join(d, "sample.py"), "w", encoding="utf-8") as f:
            f.write(SAMPLE_CODE)
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["E401", "F401"]\nignore = ["F401"]\n')

        # Config ignores F401, so only E401 is reported
        assert run_ruff_check(d, "sample.py") == ["E401"]

        # CLI --select overrides config ignore and reports F401
        assert run_ruff_check(d, "--select", "F401", "sample.py") == ["F401", "F401"]


def test_per_file_ignores_replacement_vs_composition():
    """Assert per-file-ignores overwrites map while extend-per-file-ignores merges."""
    with tempfile.TemporaryDirectory() as d:
        with open(os.path.join(d, "sample.py"), "w", encoding="utf-8") as f:
            f.write(SAMPLE_CODE)
        with open(os.path.join(d, "ruff.toml"), "w", encoding="utf-8") as f:
            f.write('[lint]\nselect = ["F401", "E401"]\nper-file-ignores = {"sample.py" = ["F401"]}\n')

        # Baseline: F401 is ignored for sample.py, leaving E401
        assert run_ruff_check(d, "sample.py") == ["E401"]

        # extend-per-file-ignores merges: ignores both F401 and E401 -> 0 errors
        assert run_ruff_check(d, "--extend-per-file-ignores", "sample.py:E401", "sample.py") == []

        # per-file-ignores replaces: only E401 ignored, F401 re-appears
        assert run_ruff_check(d, "--per-file-ignores", "sample.py:E401", "sample.py") == ["F401", "F401"]


if __name__ == "__main__":
    test_same_directory_file_precedence()
    test_directory_hierarchy_and_extend()
    test_select_vs_extend_select_composition()
    test_cli_select_overrides_ignore()
    test_per_file_ignores_replacement_vs_composition()
    print("CONTRACT PASS: Ruff configuration precedence and rule composition verified")