[CLI] Migrate bootstrap (#5059)

### Changes

This PR adds the new `casp bootstrap` command to the `casp` CLI. Which
acts as a convenient wrapper for the root `butler.py bootstrap` script.

### How it works:
   - `casp bootstrap` Install all required dependencies from Clusterfuzz

### Changes in butler

Regarding the refactor/improvement in `butler.py`, here are some
screenshots comparing running `python butler.py bootstrap` in this
branch and master. They show that the behavior is the same.

<img width="1350" height="295" alt="image"
src="https://github.com/user-attachments/assets/f608d300-5e05-48c9-9092-01687dfb76fa"
/>
<img width="1349" height="295" alt="image"
src="https://github.com/user-attachments/assets/8e2b55cb-66a5-41ac-b043-05034a17d163"
/>

<img width="1349" height="295" alt="image"
src="https://github.com/user-attachments/assets/16dcecab-57fd-481c-b6ed-a893bb576b50"
/>
<img width="1349" height="295" alt="image"
src="https://github.com/user-attachments/assets/8d22a4ec-e23d-4b38-bfaa-be48e5c995db"
/>

### Demo prints

Here are some screenshots of `casp bootstrap` in action:

<img width="1349" height="295" alt="image"
src="https://github.com/user-attachments/assets/95516c06-28bb-4765-9689-49e856e5ce10"
/>
<img width="1350" height="295" alt="image"
src="https://github.com/user-attachments/assets/7bf8e128-4582-4c5d-be48-a72bdda68210"
/>

Author: PauloVLB

butler.py

@@ -98,6 +98,14 @@ def _setup_args_for_remote(parser):
   subparsers.add_parser('reboot', help='Reboot with `sudo reboot`.')
 
 
+def _add_bootstrap_subparser(toplevel_subparsers):
+  """Adds a parser for the `bootstrap` command."""
+  toplevel_subparsers.add_parser(
+      'bootstrap',
+      help=('Install all required dependencies for running an appengine, a bot,'
+            'and a mapreduce locally.'))
+
+
 def _add_py_unittest_subparser(toplevel_subparsers):
   """Adds a parser for the `py_unittest` command."""
   parser_py_unittest = toplevel_subparsers.add_parser(
@@ -317,11 +325,6 @@ def main():
       help='Force logs to be local-only.')
   subparsers = parser.add_subparsers(dest='command')
 
-  subparsers.add_parser(
-      'bootstrap',
-      help=('Install all required dependencies for running an appengine, a bot,'
-            'and a mapreduce locally.'))
-
   parser_js_unittest = subparsers.add_parser(
       'js_unittest', help='Run Javascript unit tests.')
   parser_js_unittest.add_argument(
@@ -454,6 +457,7 @@ def main():
       default='us-central',
       help='Location for App Engine.')
 
+  _add_bootstrap_subparser(subparsers)
   _add_py_unittest_subparser(subparsers)
   _add_lint_subparser(subparsers)
   _add_format_subparser(subparsers)

cli/casp/src/casp/commands/bootstrap.py

@@ -11,16 +11,33 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-"""Bootstrap command."""
+"""Install all required dependencies from Clusterfuzz"""
 
+import subprocess
+import sys
+
+from casp.utils import local_butler
 import click
 
 
 @click.command(
     name='bootstrap',
     help=('Install all required dependencies for running an appengine, a bot,'
           'and a mapreduce locally.'))
-def cli():
-  """Install all required dependencies for running an appengine, a bot,
-  and a mapreduce locally."""
-  click.echo('To be implemented...')
+def cli() -> None:
+  """Performs the installation of all required dependencies."""
+
+  try:
+    command = local_butler.build_command('bootstrap', None)
+  except FileNotFoundError:
+    click.echo('butler.py not found in this directory.', err=True)
+    sys.exit(1)
+
+  try:
+    subprocess.run(command, check=True)
+  except FileNotFoundError:
+    click.echo('python not found in PATH.', err=True)
+    sys.exit(1)
+  except subprocess.CalledProcessError as e:
+    click.echo(f'Error running butler.py bootstrap: {e}', err=True)
+    sys.exit(1)

cli/casp/src/casp/tests/commands/bootstrap_test.py

@@ -0,0 +1,74 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Tests for the bootstrap command.
+
+  For running all the tests, use (from the root of the project):
+  python -m unittest discover -s cli/casp/src/casp/tests -p bootstrap_test.py -v
+"""
+
+import subprocess
+import unittest
+from unittest.mock import patch
+
+from casp.commands import bootstrap
+from click.testing import CliRunner
+
+
+class BootstrapCliTest(unittest.TestCase):
+  """Tests for the bootstrap command."""
+
+  def setUp(self):
+    self.runner = CliRunner()
+    self.mock_local_butler = self.enterContext(
+        patch('casp.commands.bootstrap.local_butler', autospec=True))
+    self.mock_subprocess_run = self.enterContext(
+        patch('subprocess.run', autospec=True))
+
+  def test_bootstrap_success(self):
+    """Tests successful execution of `casp bootstrap`."""
+    self.mock_local_butler.build_command.return_value = ['cmd']
+    result = self.runner.invoke(bootstrap.cli)
+    self.assertEqual(0, result.exit_code, msg=result.output)
+    self.mock_local_butler.build_command.assert_called_once_with(
+        'bootstrap', None)
+    self.mock_subprocess_run.assert_called_once_with(['cmd'], check=True)
+
+  def test_butler_not_found(self):
+    """Tests when `butler.py` is not found."""
+    self.mock_local_butler.build_command.side_effect = FileNotFoundError
+    result = self.runner.invoke(bootstrap.cli)
+    self.assertNotEqual(0, result.exit_code)
+    self.assertIn('butler.py not found', result.output)
+    self.mock_subprocess_run.assert_not_called()
+
+  def test_subprocess_run_fails(self):
+    """Tests when `subprocess.run` fails."""
+    self.mock_local_butler.build_command.return_value = ['cmd']
+    self.mock_subprocess_run.side_effect = subprocess.CalledProcessError(
+        1, 'cmd')
+    result = self.runner.invoke(bootstrap.cli)
+    self.assertNotEqual(0, result.exit_code)
+    self.assertIn('Error running butler.py bootstrap', result.output)
+
+  def test_python_not_found(self):
+    """Tests when `python` command is not found."""
+    self.mock_local_butler.build_command.return_value = ['cmd']
+    self.mock_subprocess_run.side_effect = FileNotFoundError
+    result = self.runner.invoke(bootstrap.cli)
+    self.assertNotEqual(0, result.exit_code)
+    self.assertIn('python not found in PATH', result.output)
+
+
+if __name__ == '__main__':
+  unittest.main()