1 files changed, 114 insertions, 0 deletions
diff --git a/pre_commit/languages/docker.py b/pre_commit/languages/docker.py
new file mode 100644
index 0000000..f449584
--- /dev/null
+++ b/pre_commit/languages/docker.py
@@ -0,0 +1,114 @@
+import hashlib
+import os
+from typing import Sequence
+from typing import Tuple
+
+import pre_commit.constants as C
+from pre_commit.hook import Hook
+from pre_commit.languages import helpers
+from pre_commit.prefix import Prefix
+from pre_commit.util import CalledProcessError
+from pre_commit.util import clean_path_on_failure
+from pre_commit.util import cmd_output_b
+
+ENVIRONMENT_DIR = 'docker'
+PRE_COMMIT_LABEL = 'PRE_COMMIT'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def md5(s: str) -> str:  # pragma: win32 no cover
+    return hashlib.md5(s.encode()).hexdigest()
+
+
+def docker_tag(prefix: Prefix) -> str:  # pragma: win32 no cover
+    md5sum = md5(os.path.basename(prefix.prefix_dir)).lower()
+    return f'pre-commit-{md5sum}'
+
+
+def docker_is_running() -> bool:  # pragma: win32 no cover
+    try:
+        cmd_output_b('docker', 'ps')
+    except CalledProcessError:
+        return False
+    else:
+        return True
+
+
+def assert_docker_available() -> None:  # pragma: win32 no cover
+    assert docker_is_running(), (
+        'Docker is either not running or not configured in this environment'
+    )
+
+
+def build_docker_image(
+        prefix: Prefix,
+        *,
+        pull: bool,
+) -> None:  # pragma: win32 no cover
+    cmd: Tuple[str, ...] = (
+        'docker', 'build',
+        '--tag', docker_tag(prefix),
+        '--label', PRE_COMMIT_LABEL,
+    )
+    if pull:
+        cmd += ('--pull',)
+    # This must come last for old versions of docker.  See #477
+    cmd += ('.',)
+    helpers.run_setup_cmd(prefix, cmd)
+
+
+def install_environment(
+        prefix: Prefix, version: str, additional_dependencies: Sequence[str],
+) -> None:  # pragma: win32 no cover
+    helpers.assert_version_default('docker', version)
+    helpers.assert_no_additional_deps('docker', additional_dependencies)
+    assert_docker_available()
+
+    directory = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, C.DEFAULT),
+    )
+
+    # Docker doesn't really have relevant disk environment, but pre-commit
+    # still needs to cleanup its state files on failure
+    with clean_path_on_failure(directory):
+        build_docker_image(prefix, pull=True)
+        os.mkdir(directory)
+
+
+def get_docker_user() -> str:  # pragma: win32 no cover
+    try:
+        return f'{os.getuid()}:{os.getgid()}'
+    except AttributeError:
+        return '1000:1000'
+
+
+def docker_cmd() -> Tuple[str, ...]:  # pragma: win32 no cover
+    return (
+        'docker', 'run',
+        '--rm',
+        '-u', get_docker_user(),
+        # https://docs.docker.com/engine/reference/commandline/run/#mount-volumes-from-container-volumes-from
+        # The `Z` option tells Docker to label the content with a private
+        # unshared label. Only the current container can use a private volume.
+        '-v', f'{os.getcwd()}:/src:rw,Z',
+        '--workdir', '/src',
+    )
+
+
+def run_hook(
+        hook: Hook,
+        file_args: Sequence[str],
+        color: bool,
+) -> Tuple[int, bytes]:  # pragma: win32 no cover
+    assert_docker_available()
+    # Rebuild the docker image in case it has gone missing, as many people do
+    # automated cleanup of docker images.
+    build_docker_image(hook.prefix, pull=False)
+
+    hook_cmd = hook.cmd
+    entry_exe, cmd_rest = hook.cmd[0], hook_cmd[1:]
+
+    entry_tag = ('--entrypoint', entry_exe, docker_tag(hook.prefix))
+    cmd = docker_cmd() + entry_tag + cmd_rest
+    return helpers.run_xargs(hook, cmd, file_args, color=color)