Support ruby through a combination of rbenv, ruby-build, and GEM_HOME

pre_commit/languages/ruby.py

@@ -1,16 +1,25 @@
+from __future__ import unicode_literals
+
 import contextlib
+import io
+import os
 
 from pre_commit.languages import helpers
 from pre_commit.util import clean_path_on_failure
 
 
-ENVIRONMENT_DIR = 'rvm_env'
+ENVIRONMENT_DIR = 'rbenv'
 
 
 class RubyEnv(helpers.Environment):
     @property
     def env_prefix(self):
-        raise NotImplementedError
+        return '. {{prefix}}{0}/bin/activate &&'.format(ENVIRONMENT_DIR)
+
+    def run(self, *args, **kwargs):
+        # TODO: hardcoded version smell
+        env = dict(os.environ, RBENV_VERSION='1.9.3-p545')
+        return super(RubyEnv, self).run(*args, env=env, **kwargs)
 
 
 @contextlib.contextmanager
@@ -18,15 +27,44 @@ def in_env(repo_cmd_runner):
     yield RubyEnv(repo_cmd_runner)
 
 
-def install_environment(repo_cmd_runner):
-    # Return immediately if we already have a virtualenv
-    if repo_cmd_runner.exists(ENVIRONMENT_DIR):
-        return
+def _install_rbenv(repo_cmd_runner):
+    repo_cmd_runner.run([
+        'git', 'clone', 'git://github.com/sstephenson/rbenv', '{prefix}rbenv',
+    ])
+    repo_cmd_runner.run([
+        'git', 'clone', 'git://github.com/sstephenson/ruby-build',
+        '{prefix}rbenv/plugins/ruby-build',
+    ])
 
-    with clean_path_on_failure(repo_cmd_runner.path(ENVIRONMENT_DIR)):
-        repo_cmd_runner.run(['__rvm-env.sh', '{{prefix}}{0}'.format(ENVIRONMENT_DIR)])
-        with in_env(repo_cmd_runner) as env:
-            env.run('cd {prefix} && bundle install')
+    activate_path = repo_cmd_runner.path('rbenv', 'bin', 'activate')
+    with io.open(activate_path, 'w') as activate_file:
+        # This is similar to how you would install rbenv to your home directory
+        # However we do a couple things to make the executables exposed and
+        # configure it to work in our directory.
+        # We also modify the PS1 variable for manual debugging sake.
+        activate_file.write(
+            '#!/usr/bin/env bash\n'
+            "export RBENV_ROOT='{0}'\n"
+            'export PATH="$RBENV_ROOT/bin:$PATH"\n'
+            'eval "$(rbenv init -)"\n'
+            'export PS1="(rbenv)$PS1"\n'
+            # This lets us install gems in an isolated and repeatable
+            # directory
+            "export GEM_HOME='{0}/gems'\n"
+            'export PATH="$GEM_HOME/bin:$PATH"\n'
+            '\n'.format(repo_cmd_runner.path('rbenv'))
+        )
+
+
+def install_environment(repo_cmd_runner):
+    with clean_path_on_failure(repo_cmd_runner.path('rbenv')):
+        _install_rbenv(repo_cmd_runner)
+        with in_env(repo_cmd_runner) as ruby_env:
+            # TODO: hardcoded version smell
+            ruby_env.run('rbenv install 1.9.3-p545')
+            ruby_env.run(
+                'cd {prefix} && gem build *.gemspec && gem install *.gem',
+            )
 
 
 def run_hook(repo_cmd_runner, hook, file_args):