PR feedback fixes

pre_commit/languages/swift.py

@@ -1,7 +1,10 @@
 from __future__ import unicode_literals
 
+import contextlib
 import os
 
+from pre_commit.envcontext import envcontext
+from pre_commit.envcontext import Var
 from pre_commit.languages import helpers
 from pre_commit.util import clean_path_on_failure
 from pre_commit.xargs import xargs
@@ -11,11 +14,34 @@ BUILD_DIR = '.build'
 BUILD_CONFIG = 'release'
 
 
+def get_env_patch(venv):
+    bin_path = os.path.join(venv, BUILD_DIR, BUILD_CONFIG)
+    patches = (
+        ('PATH', (
+            bin_path, os.pathsep, Var('PATH'),
+        )),
+    )
+    return patches
+
+
+@contextlib.contextmanager
+def in_env(repo_cmd_runner):
+    envdir = os.path.join(
+        repo_cmd_runner.prefix_dir,
+        helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
+    )
+    with envcontext(get_env_patch(envdir)):
+        yield
+
+
 def install_environment(
         repo_cmd_runner,
         version='default',
         additional_dependencies=(),
 ):
+    assert version == 'default', (
+        'Pre-commit does not support language_version for docker '
+    )
     directory = repo_cmd_runner.path(helpers.environment_dir(
         ENVIRONMENT_DIR, 'default',
     ))
@@ -32,9 +58,5 @@ def install_environment(
 
 
 def run_hook(repo_cmd_runner, hook, file_args):
-    directory = repo_cmd_runner.path(helpers.environment_dir(
+    with in_env(repo_cmd_runner):
-        ENVIRONMENT_DIR, 'default',
+        return xargs(helpers.to_cmd(hook), file_args)
-    ))
-    cmd = helpers.to_cmd(hook)
-    full_binary_path = os.path.join(directory, BUILD_DIR, BUILD_CONFIG, cmd[0])
-    return xargs((full_binary_path,) + cmd[1:], file_args)