tests/utils_for_test.py

# Copyright (C) 2026 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Various utility code used by tests.

If you want to write a per-test fixture, see conftest.py instead.
"""

import contextlib
import functools
from pathlib import Path
import subprocess
import tempfile
from typing import Optional, Union

import git_command


def init_git_tree(
    path: Union[str, Path],
    ref_format: Optional[str] = None,
) -> None:
    """Initialize `path` as a new git repo."""
    with contextlib.ExitStack() as stack:
        # Tests need to assume, that main is default branch at init,
        # which is not supported in config until 2.28.
        cmd = ["git"]
        if ref_format:
            cmd += ["-c", f"init.defaultRefFormat={ref_format}"]
        cmd += ["init"]

        if git_command.git_require((2, 28, 0)):
            cmd += ["--initial-branch=main"]
        else:
            # Use template dir for init.
            templatedir = stack.enter_context(
                tempfile.mkdtemp(prefix="git-template")
            )
            (Path(templatedir) / "HEAD").write_text("ref: refs/heads/main\n")
            cmd += ["--template", templatedir]
        cmd += [path]
        subprocess.run(cmd, check=True)


@contextlib.contextmanager
def TempGitTree():
    """Create a new empty git checkout for testing."""
    with tempfile.TemporaryDirectory(prefix="repo-tests") as tempdir:
        init_git_tree(tempdir)
        yield tempdir


@functools.lru_cache(maxsize=None)
def supports_reftable() -> bool:
    """Check if git supports reftable."""
    with tempfile.TemporaryDirectory(prefix="repo-tests") as tempdir:
        proc = subprocess.run(
            ["git", "-c", "init.defaultRefFormat=reftable", "init"],
            cwd=tempdir,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            check=False,
        )
    return proc.returncode == 0


@functools.lru_cache(maxsize=None)
def supports_refs_migrate() -> bool:
    """Check if git supports refs migrate."""
    with tempfile.TemporaryDirectory(prefix="repo-tests") as tempdir:
        subprocess.check_call(
            ["git", "-c", "init.defaultRefFormat=files", "init"],
            cwd=tempdir,
        )
        proc = subprocess.run(
            [
                "git",
                "refs",
                "migrate",
                "--ref-format=reftable",
                "--dry-run",
            ],
            cwd=tempdir,
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
            check=False,
        )
    return proc.returncode == 0