1 files changed, 196 insertions, 0 deletions
diff --git a/pre_commit/lang_base.py b/pre_commit/lang_base.py
new file mode 100644
index 0000000..9480c55
--- /dev/null
+++ b/pre_commit/lang_base.py
@@ -0,0 +1,196 @@
+from __future__ import annotations
+
+import contextlib
+import multiprocessing
+import os
+import random
+import re
+import shlex
+from typing import Any
+from typing import ContextManager
+from typing import Generator
+from typing import NoReturn
+from typing import Protocol
+from typing import Sequence
+
+import pre_commit.constants as C
+from pre_commit import parse_shebang
+from pre_commit.prefix import Prefix
+from pre_commit.util import cmd_output_b
+from pre_commit.xargs import xargs
+
+FIXED_RANDOM_SEED = 1542676187
+
+SHIMS_RE = re.compile(r'[/\\]shims[/\\]')
+
+
+class Language(Protocol):
+    # Use `None` for no installation / environment
+    @property
+    def ENVIRONMENT_DIR(self) -> str | None: ...
+    # return a value to replace `'default` for `language_version`
+    def get_default_version(self) -> str: ...
+    # return whether the environment is healthy (or should be rebuilt)
+    def health_check(self, prefix: Prefix, version: str) -> str | None: ...
+
+    # install a repository for the given language and language_version
+    def install_environment(
+            self,
+            prefix: Prefix,
+            version: str,
+            additional_dependencies: Sequence[str],
+    ) -> None:
+        ...
+
+    # modify the environment for hook execution
+    def in_env(self, prefix: Prefix, version: str) -> ContextManager[None]: ...
+
+    # execute a hook and return the exit code and output
+    def run_hook(
+            self,
+            prefix: Prefix,
+            entry: str,
+            args: Sequence[str],
+            file_args: Sequence[str],
+            *,
+            is_local: bool,
+            require_serial: bool,
+            color: bool,
+    ) -> tuple[int, bytes]:
+        ...
+
+
+def exe_exists(exe: str) -> bool:
+    found = parse_shebang.find_executable(exe)
+    if found is None:  # exe exists
+        return False
+
+    homedir = os.path.expanduser('~')
+    try:
+        common: str | None = os.path.commonpath((found, homedir))
+    except ValueError:  # on windows, different drives raises ValueError
+        common = None
+
+    return (
+        # it is not in a /shims/ directory
+        not SHIMS_RE.search(found) and
+        (
+            # the homedir is / (docker, service user, etc.)
+            os.path.dirname(homedir) == homedir or
+            # the exe is not contained in the home directory
+            common != homedir
+        )
+    )
+
+
+def setup_cmd(prefix: Prefix, cmd: tuple[str, ...], **kwargs: Any) -> None:
+    cmd_output_b(*cmd, cwd=prefix.prefix_dir, **kwargs)
+
+
+def environment_dir(prefix: Prefix, d: str, language_version: str) -> str:
+    return prefix.path(f'{d}-{language_version}')
+
+
+def assert_version_default(binary: str, version: str) -> None:
+    if version != C.DEFAULT:
+        raise AssertionError(
+            f'for now, pre-commit requires system-installed {binary} -- '
+            f'you selected `language_version: {version}`',
+        )
+
+
+def assert_no_additional_deps(
+        lang: str,
+        additional_deps: Sequence[str],
+) -> None:
+    if additional_deps:
+        raise AssertionError(
+            f'for now, pre-commit does not support '
+            f'additional_dependencies for {lang} -- '
+            f'you selected `additional_dependencies: {additional_deps}`',
+        )
+
+
+def basic_get_default_version() -> str:
+    return C.DEFAULT
+
+
+def basic_health_check(prefix: Prefix, language_version: str) -> str | None:
+    return None
+
+
+def no_install(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> NoReturn:
+    raise AssertionError('This language is not installable')
+
+
+@contextlib.contextmanager
+def no_env(prefix: Prefix, version: str) -> Generator[None, None, None]:
+    yield
+
+
+def target_concurrency() -> int:
+    if 'PRE_COMMIT_NO_CONCURRENCY' in os.environ:
+        return 1
+    else:
+        # Travis appears to have a bunch of CPUs, but we can't use them all.
+        if 'TRAVIS' in os.environ:
+            return 2
+        else:
+            try:
+                return multiprocessing.cpu_count()
+            except NotImplementedError:
+                return 1
+
+
+def _shuffled(seq: Sequence[str]) -> list[str]:
+    """Deterministically shuffle"""
+    fixed_random = random.Random()
+    fixed_random.seed(FIXED_RANDOM_SEED, version=1)
+
+    seq = list(seq)
+    fixed_random.shuffle(seq)
+    return seq
+
+
+def run_xargs(
+        cmd: tuple[str, ...],
+        file_args: Sequence[str],
+        *,
+        require_serial: bool,
+        color: bool,
+) -> tuple[int, bytes]:
+    if require_serial:
+        jobs = 1
+    else:
+        # Shuffle the files so that they more evenly fill out the xargs
+        # partitions, but do it deterministically in case a hook cares about
+        # ordering.
+        file_args = _shuffled(file_args)
+        jobs = target_concurrency()
+    return xargs(cmd, file_args, target_concurrency=jobs, color=color)
+
+
+def hook_cmd(entry: str, args: Sequence[str]) -> tuple[str, ...]:
+    return (*shlex.split(entry), *args)
+
+
+def basic_run_hook(
+        prefix: Prefix,
+        entry: str,
+        args: Sequence[str],
+        file_args: Sequence[str],
+        *,
+        is_local: bool,
+        require_serial: bool,
+        color: bool,
+) -> tuple[int, bytes]:
+    return run_xargs(
+        hook_cmd(entry, args),
+        file_args,
+        require_serial=require_serial,
+        color=color,
+    )