1 files changed, 109 insertions, 0 deletions
diff --git a/pre_commit/languages/helpers.py b/pre_commit/languages/helpers.py
new file mode 100644
index 0000000..b5c95e5
--- /dev/null
+++ b/pre_commit/languages/helpers.py
@@ -0,0 +1,109 @@
+import multiprocessing
+import os
+import random
+from typing import Any
+from typing import List
+from typing import Optional
+from typing import overload
+from typing import Sequence
+from typing import Tuple
+from typing import TYPE_CHECKING
+
+import pre_commit.constants as C
+from pre_commit.hook import Hook
+from pre_commit.prefix import Prefix
+from pre_commit.util import cmd_output_b
+from pre_commit.xargs import xargs
+
+if TYPE_CHECKING:
+    from typing import NoReturn
+
+FIXED_RANDOM_SEED = 1542676186
+
+
+def run_setup_cmd(prefix: Prefix, cmd: Tuple[str, ...]) -> None:
+    cmd_output_b(*cmd, cwd=prefix.prefix_dir)
+
+
+@overload
+def environment_dir(d: None, language_version: str) -> None: ...
+@overload
+def environment_dir(d: str, language_version: str) -> str: ...
+
+
+def environment_dir(d: Optional[str], language_version: str) -> Optional[str]:
+    if d is None:
+        return None
+    else:
+        return 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}',
+        )
+
+
+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}',
+        )
+
+
+def basic_get_default_version() -> str:
+    return C.DEFAULT
+
+
+def basic_healthy(prefix: Prefix, language_version: str) -> bool:
+    return True
+
+
+def no_install(
+        prefix: Prefix,
+        version: str,
+        additional_dependencies: Sequence[str],
+) -> 'NoReturn':
+    raise AssertionError('This type is not installable')
+
+
+def target_concurrency(hook: Hook) -> int:
+    if hook.require_serial or '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)
+    random.shuffle(seq, random=fixed_random.random)
+    return seq
+
+
+def run_xargs(
+        hook: Hook,
+        cmd: Tuple[str, ...],
+        file_args: Sequence[str],
+        **kwargs: Any,
+) -> Tuple[int, bytes]:
+    # 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)
+    kwargs['target_concurrency'] = target_concurrency(hook)
+    return xargs(cmd, file_args, **kwargs)