feat: add a --clean-cache command to clean up locations specified at CIBW_CACHE_PATH (#2489)

* Add `clean_cache` to command-line arguments

* Add `--clean-cache` to parser

* Add logic

* Add test to clean cache when it exists

* Ad test to run cache cleaning when none exists

* Add test to run cache cleaning on unwritable path

* Use `main()` instead

* tests: move command tests

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Create cibuildwheel cache sentinel file

* Add sentinel to existing tests + add new test

* Add signature and switch to `CACHEDIR.TAG`

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Another instance to replace with `CACHEDIR.TAG`

* Verify `CACHEDIR.TAG` signature

* Simplify code branching and control flow

* Add test

* Add link to `CACHEDIR.TAG` specification

* Write with UTF-8 encoding

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

cibuildwheel/__main__.py

@@ -23,7 +23,7 @@ from cibuildwheel.options import CommandLineArguments, Options, compute_options
 from cibuildwheel.platforms import ALL_PLATFORM_MODULES, get_build_identifiers, native_platform
 from cibuildwheel.selector import BuildSelector, EnableGroup, selector_matches
 from cibuildwheel.typing import PLATFORMS, PlatformName
-from cibuildwheel.util.file import CIBW_CACHE_PATH
+from cibuildwheel.util.file import CIBW_CACHE_PATH, ensure_cache_sentinel
 from cibuildwheel.util.helpers import strtobool
 from cibuildwheel.util.resources import read_all_configs
 
@@ -179,6 +179,12 @@ def main_inner(global_options: GlobalOptions) -> None:
         help="Print the build identifiers matched by the current invocation and exit.",
     )
 
+    parser.add_argument(
+        "--clean-cache",
+        action="store_true",
+        help="Clear the cibuildwheel cache and exit.",
+    )
+
     parser.add_argument(
         "--allow-empty",
         action="store_true",
@@ -196,6 +202,48 @@ def main_inner(global_options: GlobalOptions) -> None:
 
     global_options.print_traceback_on_error = args.debug_traceback
 
+    if args.clean_cache:
+        if not CIBW_CACHE_PATH.exists():
+            print(f"Cache directory does not exist: {CIBW_CACHE_PATH}")
+            sys.exit(0)
+
+        sentinel_file = CIBW_CACHE_PATH / "CACHEDIR.TAG"
+        if not sentinel_file.exists():
+            print(
+                f"Error: {CIBW_CACHE_PATH} does not appear to be a cibuildwheel cache directory.",
+                "Only directories with a CACHEDIR.TAG sentinel file can be cleaned.",
+                sep="\n",
+                file=sys.stderr,
+            )
+            sys.exit(1)
+
+        # Verify signature to ensure it's a proper cache dir
+        # See https://bford.info/cachedir/ for more
+        try:
+            sentinel_content = sentinel_file.read_text(encoding="utf-8")
+        except OSError as e:
+            print(f"Error reading cache directory tag: {e}", file=sys.stderr)
+            sys.exit(1)
+
+        if not sentinel_content.startswith("Signature: 8a477f597d28d172789f06886806bc55"):
+            print(
+                f"Error: {sentinel_file} does not contain a valid cache directory signature.",
+                "For safety, only properly signed cache directories can be cleaned.",
+                sep="\n",
+                file=sys.stderr,
+            )
+            sys.exit(1)
+
+        print(f"Clearing cache directory: {CIBW_CACHE_PATH}")
+        try:
+            shutil.rmtree(CIBW_CACHE_PATH)
+            print("Cache cleared successfully.")
+        except OSError as e:
+            print(f"Error clearing cache: {e}", file=sys.stderr)
+            sys.exit(1)
+
+        sys.exit(0)
+
     args.package_dir = args.package_dir.resolve()
 
     # This are always relative to the base directory, even in SDist builds
@@ -309,6 +357,7 @@ def build_in_directory(args: CommandLineArguments) -> None:
 
     # create the cache dir before it gets printed & builds performed
     CIBW_CACHE_PATH.mkdir(parents=True, exist_ok=True)
+    ensure_cache_sentinel(CIBW_CACHE_PATH)
 
     print_preamble(platform=platform, options=options, identifiers=identifiers)
 

cibuildwheel/options.py

@@ -63,6 +63,7 @@ class CommandLineArguments:
     allow_empty: bool
     debug_traceback: bool
     enable: list[str]
+    clean_cache: bool
 
     @classmethod
     def defaults(cls) -> Self:
@@ -77,6 +78,7 @@ class CommandLineArguments:
             print_build_identifiers=False,
             debug_traceback=False,
             enable=[],
+            clean_cache=False,
         )
 
 

cibuildwheel/util/file.py

@@ -20,6 +20,26 @@ CIBW_CACHE_PATH: Final[Path] = Path(
 ).resolve()
 
 
+def ensure_cache_sentinel(cache_path: Path) -> None:
+    """Create a sentinel file to mark a cibuildwheel cache directory.
+
+    We help prevent accidental deletion of non-cache directories with this.
+
+    Args:
+        cache_path: The cache directory path where the sentinel should be created
+    """
+    if cache_path.exists():
+        sentinel_file = cache_path / "CACHEDIR.TAG"
+        if not sentinel_file.exists():
+            sentinel_file.write_text(
+                "Signature: 8a477f597d28d172789f06886806bc55\n"
+                "# This file is a cache directory tag created by cibuildwheel.\n"
+                "# For information about cache directory tags, see:\n"
+                "# https://www.brynosaurus.com/cachedir/",
+                encoding="utf-8",
+            )
+
+
 def download(url: str, dest: Path) -> None:
     print(f"+ Download {url} to {dest}")
     dest_dir = dest.parent

unit_test/main_commands_test.py

@@ -0,0 +1,127 @@
+import errno
+import shutil
+import sys
+
+import pytest
+
+import cibuildwheel.__main__ as main_module
+from cibuildwheel.__main__ import main
+
+
+def test_clean_cache_when_cache_exists(tmp_path, monkeypatch, capfd):
+    fake_cache_dir = (tmp_path / "cibw_cache").resolve()
+    monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
+
+    fake_cache_dir.mkdir(parents=True, exist_ok=True)
+    assert fake_cache_dir.exists()
+
+    cibw_sentinel = fake_cache_dir / "CACHEDIR.TAG"
+    cibw_sentinel.write_text(
+        "Signature: 8a477f597d28d172789f06886806bc55\n"
+        "# This file is a cache directory tag created by cibuildwheel.\n"
+        "# For information about cache directory tags, see:\n"
+        "# https://www.brynosaurus.com/cachedir/",
+        encoding="utf-8",
+    )
+
+    dummy_file = fake_cache_dir / "dummy.txt"
+    dummy_file.write_text("hello")
+
+    monkeypatch.setattr(sys, "argv", ["cibuildwheel", "--clean-cache"])
+
+    with pytest.raises(SystemExit) as e:
+        main()
+
+    assert e.value.code == 0
+
+    out, err = capfd.readouterr()
+    assert f"Clearing cache directory: {fake_cache_dir}" in out
+    assert "Cache cleared successfully." in out
+    assert not fake_cache_dir.exists()
+
+
+def test_clean_cache_when_cache_does_not_exist(tmp_path, monkeypatch, capfd):
+    fake_cache_dir = (tmp_path / "nonexistent_cache").resolve()
+    monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
+
+    monkeypatch.setattr(sys, "argv", ["cibuildwheel", "--clean-cache"])
+
+    with pytest.raises(SystemExit) as e:
+        main()
+
+    assert e.value.code == 0
+
+    out, err = capfd.readouterr()
+    assert f"Cache directory does not exist: {fake_cache_dir}" in out
+
+
+def test_clean_cache_with_error(tmp_path, monkeypatch, capfd):
+    fake_cache_dir = (tmp_path / "cibw_cache").resolve()
+    monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
+
+    fake_cache_dir.mkdir(parents=True, exist_ok=True)
+    assert fake_cache_dir.exists()
+
+    cibw_sentinel = fake_cache_dir / "CACHEDIR.TAG"
+    cibw_sentinel.write_text(
+        "Signature: 8a477f597d28d172789f06886806bc55\n"
+        "# This file is a cache directory tag created by cibuildwheel.\n"
+        "# For information about cache directory tags, see:\n"
+        "# https://www.brynosaurus.com/cachedir/",
+        encoding="utf-8",
+    )
+
+    monkeypatch.setattr(sys, "argv", ["cibuildwheel", "--clean-cache"])
+
+    def fake_rmtree(path):  # noqa: ARG001
+        raise OSError(errno.EACCES, "Permission denied")
+
+    monkeypatch.setattr(shutil, "rmtree", fake_rmtree)
+
+    with pytest.raises(SystemExit) as e:
+        main()
+
+    assert e.value.code == 1
+
+    out, err = capfd.readouterr()
+    assert f"Clearing cache directory: {fake_cache_dir}" in out
+    assert "Error clearing cache:" in err
+
+
+def test_clean_cache_without_sentinel(tmp_path, monkeypatch, capfd):
+    fake_cache_dir = (tmp_path / "not_a_cache").resolve()
+    monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
+
+    fake_cache_dir.mkdir(parents=True, exist_ok=True)
+
+    monkeypatch.setattr(sys, "argv", ["cibuildwheel", "--clean-cache"])
+
+    with pytest.raises(SystemExit) as e:
+        main()
+
+    assert e.value.code == 1
+
+    out, err = capfd.readouterr()
+    assert "does not appear to be a cibuildwheel cache directory" in err
+    assert fake_cache_dir.exists()
+
+
+def test_clean_cache_with_invalid_signature(tmp_path, monkeypatch, capfd):
+    fake_cache_dir = (tmp_path / "fake_cache").resolve()
+    monkeypatch.setattr(main_module, "CIBW_CACHE_PATH", fake_cache_dir)
+
+    fake_cache_dir.mkdir(parents=True, exist_ok=True)
+
+    cibw_sentinel = fake_cache_dir / "CACHEDIR.TAG"
+    cibw_sentinel.write_text("Invalid signature\n# This is not a real cache directory tag")
+
+    monkeypatch.setattr(sys, "argv", ["cibuildwheel", "--clean-cache"])
+
+    with pytest.raises(SystemExit) as e:
+        main()
+
+    assert e.value.code == 1
+
+    out, err = capfd.readouterr()
+    assert "does not contain a valid cache directory signature" in err
+    assert fake_cache_dir.exists()