Add Rust support

pre_commit/languages/all.py

@@ -9,6 +9,7 @@ from pre_commit.languages import pygrep
 from pre_commit.languages import python
 from pre_commit.languages import python_venv
 from pre_commit.languages import ruby
+from pre_commit.languages import rust
 from pre_commit.languages import script
 from pre_commit.languages import swift
 from pre_commit.languages import system
@@ -60,6 +61,7 @@ languages = {
     'python': python,
     'python_venv': python_venv,
     'ruby': ruby,
+    'rust': rust,
     'script': script,
     'swift': swift,
     'system': system,

pre_commit/languages/rust.py

@@ -0,0 +1,68 @@
+from __future__ import unicode_literals
+
+import contextlib
+import os.path
+
+import toml
+
+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.util import cmd_output
+from pre_commit.xargs import xargs
+
+
+ENVIRONMENT_DIR = 'rustenv'
+get_default_version = helpers.basic_get_default_version
+healthy = helpers.basic_healthy
+
+
+def get_env_patch(target_dir):
+    return (
+        (
+            'PATH',
+            (os.path.join(target_dir, 'release'), os.pathsep, Var('PATH')),
+        ),
+    )
+
+
+@contextlib.contextmanager
+def in_env(prefix):
+    target_dir = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
+    )
+    with envcontext(get_env_patch(target_dir)):
+        yield
+
+
+def _add_dependencies(cargo_toml_path, additional_dependencies):
+    with open(cargo_toml_path, 'r+') as f:
+        cargo_toml = toml.load(f)
+        for dep in additional_dependencies:
+            name, _, spec = dep.partition(':')
+            cargo_toml['dependencies'][name] = spec or '*'
+        f.seek(0)
+        toml.dump(cargo_toml, f)
+        f.truncate()
+
+
+def install_environment(prefix, version, additional_dependencies):
+    helpers.assert_version_default('rust', version)
+    directory = prefix.path(
+        helpers.environment_dir(ENVIRONMENT_DIR, 'default'),
+    )
+
+    if len(additional_dependencies) > 0:
+        _add_dependencies(prefix.path('Cargo.toml'), additional_dependencies)
+
+    with clean_path_on_failure(directory):
+        cmd_output(
+            'cargo', 'build', '--release', '--bins', '--target-dir', directory,
+            cwd=prefix.prefix_dir,
+        )
+
+
+def run_hook(prefix, hook, file_args):
+    with in_env(prefix):
+        return xargs(helpers.to_cmd(hook), file_args)

setup.py

@@ -42,6 +42,7 @@ setup(
         'nodeenv>=0.11.1',
         'pyyaml',
         'six',
+        'toml',
         'virtualenv',
     ],
     entry_points={