Add error_handler and use it.

pre_commit/error_handler.py

@@ -0,0 +1,42 @@
+from __future__ import absolute_import
+from __future__ import print_function
+from __future__ import unicode_literals
+
+import contextlib
+import io
+import os.path
+import traceback
+
+from pre_commit.errors import FatalError
+from pre_commit.store import Store
+
+
+# For testing purposes
+class PreCommitSystemExit(SystemExit):
+    pass
+
+
+def _log_and_exit(msg, exc, formatted, print_fn=print):
+    error_msg = '{0}: {1}: {2}'.format(msg, type(exc).__name__, exc)
+    print_fn(error_msg)
+    print_fn('Check the log at ~/.pre-commit/pre-commit.log')
+    store = Store()
+    store.require_created()
+    with io.open(os.path.join(store.directory, 'pre-commit.log'), 'w') as log:
+        log.write(error_msg + '\n')
+        log.write(formatted + '\n')
+    raise PreCommitSystemExit(1)
+
+
+@contextlib.contextmanager
+def error_handler():
+    try:
+        yield
+    except FatalError as e:
+        _log_and_exit('An error has occurred', e, traceback.format_exc())
+    except Exception as e:
+        _log_and_exit(
+            'An unexpected error has occurred',
+            e,
+            traceback.format_exc(),
+        )

pre_commit/errors.py

@@ -0,0 +1,6 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+
+class FatalError(RuntimeError):
+    pass

pre_commit/five.py

@@ -1,6 +1,5 @@
 from __future__ import unicode_literals
 
-"""five: six, redux"""
 # pylint:disable=invalid-name
 PY2 = str is bytes
 PY3 = str is not bytes

pre_commit/jsonschema_extensions.py

@@ -20,20 +20,20 @@ def extend_validator_cls(validator_cls, modify):
 
 
 def default_values(properties, instance):
-    for property, subschema in properties.items():
+    for prop, subschema in properties.items():
         if 'default' in subschema:
             instance.setdefault(
-                property, copy.deepcopy(subschema['default']),
+                prop, copy.deepcopy(subschema['default']),
             )
 
 
 def remove_default_values(properties, instance):
-    for property, subschema in properties.items():
+    for prop, subschema in properties.items():
         if (
                 'default' in subschema and
-            instance.get(property) == subschema['default']
+                instance.get(prop) == subschema['default']
         ):
-            del instance[property]
+            del instance[prop]
 
 
 _AddDefaultsValidator = extend_validator_cls(

pre_commit/main.py

@@ -9,6 +9,7 @@ from pre_commit.commands.clean import clean
 from pre_commit.commands.install_uninstall import install
 from pre_commit.commands.install_uninstall import uninstall
 from pre_commit.commands.run import run
+from pre_commit.error_handler import error_handler
 from pre_commit.runner import Runner
 from pre_commit.util import entry
 
@@ -83,6 +84,7 @@ def main(argv):
         else:
             parser.parse_args(['--help'])
 
+    with error_handler():
         runner = Runner.create()
 
         if args.command == 'install':

pylintrc

@@ -1,5 +1,5 @@
 [MESSAGES CONTROL]
-disable=missing-docstring,abstract-method,redefined-builtin,useless-else-on-loop,redefined-outer-name,invalid-name
+disable=locally-disabled,fixme,missing-docstring,abstract-method,useless-else-on-loop,invalid-name
 
 [REPORTS]
 output-format=colorized

tests/error_handler_test.py

@@ -0,0 +1,93 @@
+from __future__ import absolute_import
+from __future__ import unicode_literals
+
+import io
+import os.path
+import mock
+import pytest
+import re
+
+from pre_commit import error_handler
+from pre_commit.errors import FatalError
+
+
+@pytest.yield_fixture
+def mocked_log_and_exit():
+    with mock.patch.object(error_handler, '_log_and_exit') as log_and_exit:
+        yield log_and_exit
+
+
+def test_error_handler_no_exception(mocked_log_and_exit):
+    with error_handler.error_handler():
+        pass
+    assert mocked_log_and_exit.call_count == 0
+
+
+def test_error_handler_fatal_error(mocked_log_and_exit):
+    exc = FatalError('just a test')
+    with error_handler.error_handler():
+        raise exc
+
+    mocked_log_and_exit.assert_called_once_with(
+        'An error has occurred',
+        exc,
+        # Tested below
+        mock.ANY,
+    )
+
+    assert re.match(
+        'Traceback \(most recent call last\):\n'
+        '  File ".+/pre_commit/error_handler.py", line \d+, in error_handler\n'
+        '    yield\n'
+        '  File ".+/tests/error_handler_test.py", line \d+, '
+        'in test_error_handler_fatal_error\n'
+        '    raise exc\n'
+        '(pre_commit\.errors\.)?FatalError: just a test\n',
+        mocked_log_and_exit.call_args[0][2],
+    )
+
+
+def test_error_handler_uncaught_error(mocked_log_and_exit):
+    exc = ValueError('another test')
+    with error_handler.error_handler():
+        raise exc
+
+    mocked_log_and_exit.assert_called_once_with(
+        'An unexpected error has occurred',
+        exc,
+        # Tested below
+        mock.ANY,
+    )
+    assert re.match(
+        'Traceback \(most recent call last\):\n'
+        '  File ".+/pre_commit/error_handler.py", line \d+, in error_handler\n'
+        '    yield\n'
+        '  File ".+/tests/error_handler_test.py", line \d+, '
+        'in test_error_handler_uncaught_error\n'
+        '    raise exc\n'
+        'ValueError: another test\n',
+        mocked_log_and_exit.call_args[0][2],
+    )
+
+
+def test_log_and_exit(mock_out_store_directory):
+    mocked_print = mock.Mock()
+    with pytest.raises(error_handler.PreCommitSystemExit):
+        error_handler._log_and_exit(
+            'msg', FatalError('hai'), "I'm a stacktrace",
+            print_fn=mocked_print,
+        )
+
+    printed = '\n'.join(call[0][0] for call in mocked_print.call_args_list)
+    assert printed == (
+        'msg: FatalError: hai\n'
+        'Check the log at ~/.pre-commit/pre-commit.log'
+    )
+
+    log_file = os.path.join(mock_out_store_directory, 'pre-commit.log')
+    assert os.path.exists(log_file)
+    contents = io.open(log_file).read()
+    assert contents == (
+        'msg: FatalError: hai\n'
+        "I'm a stacktrace\n"
+    )