Refactor into Python package format (#1165)

* Refactor into a python module format

-Updates import statements to be absolute vs implicitly relative
-Uses import syntax that minimizes the need to update references in code
and/or reformat affected lines (e.g. `import gapi.directory` becomes `from gam.gapi import directory as
gapi_directory`)
-Adds a `__main__.py` such that the module can be executed on its own
using standard `python3 -m gam` syntax
-Replaces __main__ import hack with module import
-Updates the GAM path to be the module's parent dir

* Add gam.py to /src for backwards compatibility

A stub that calls gam.__main__.main() to be used by users who are not
with the syntax of calling a module implementation. It should also
provide immediate backwards-compatibility with existing scripts with
references to this file.

* Move build tools back to the main dir and out of the package

* Fix pylint errors

* Update build spec to use new package format

Incorporates @jay0lee's patch from
https://github.com/jay0lee/GAM/pull/1165#issuecomment-618430828

src/gam/fileutils_test.py

@@ -0,0 +1,234 @@
+"""Tests for fileutils."""
+
+import io
+import os
+import unittest
+from unittest.mock import MagicMock
+from unittest.mock import patch
+
+from gam import fileutils
+
+
+class FileutilsTest(unittest.TestCase):
+
+  def setUp(self):
+    self.fake_path = '/some/path/to/file'
+    super(FileutilsTest, self).setUp()
+
+  @patch.object(fileutils.sys, 'stdin')
+  def test_open_file_stdin(self, mock_stdin):
+    mock_stdin.read.return_value = 'some stdin content'
+    f = fileutils.open_file('-', mode='r')
+    self.assertIsInstance(f, fileutils.io.StringIO)
+    self.assertEqual(f.getvalue(), mock_stdin.read.return_value)
+
+  def test_open_file_stdout(self):
+    f = fileutils.open_file('-', mode='w')
+    self.assertEqual(fileutils.sys.stdout, f)
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_opens_correct_path(self, mock_open):
+    f = fileutils.open_file(self.fake_path)
+    self.assertEqual(self.fake_path, mock_open.call_args[0][0])
+    self.assertEqual(mock_open.return_value, f)
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_expands_user_file_path(self, mock_open):
+    file_path = '~/some/path/containing/tilde/shortcut/to/home'
+    fileutils.open_file(file_path)
+    opened_path = mock_open.call_args[0][0]
+    home_path = os.environ.get('HOME')
+    self.assertIsNotNone(home_path)
+    self.assertIn(home_path, opened_path)
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_opens_correct_mode(self, mock_open):
+    fileutils.open_file(self.fake_path)
+    self.assertEqual('r', mock_open.call_args[0][1])
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_encoding_for_binary(self, mock_open):
+    fileutils.open_file(self.fake_path, mode='b')
+    self.assertIsNone(mock_open.call_args[1]['encoding'])
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_default_system_encoding(self, mock_open):
+    fileutils.open_file(self.fake_path)
+    self.assertEqual(fileutils.GM_Globals[fileutils.GM_SYS_ENCODING],
+                     mock_open.call_args[1]['encoding'])
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_utf8_encoding_specified(self, mock_open):
+    fileutils.open_file(self.fake_path, encoding='UTF-8')
+    self.assertEqual(fileutils.UTF8_SIG, mock_open.call_args[1]['encoding'])
+
+  def test_open_file_strips_utf_bom_in_utf(self):
+    bom_prefixed_data = u'\ufefffoobar'
+    fake_file = io.StringIO(bom_prefixed_data)
+    mock_open = MagicMock(spec=open, return_value=fake_file)
+    with patch.object(fileutils, 'open', mock_open):
+      f = fileutils.open_file(self.fake_path, strip_utf_bom=True)
+      self.assertEqual('foobar', f.read())
+
+  def test_open_file_strips_utf_bom_in_non_utf(self):
+    bom_prefixed_data = b'\xef\xbb\xbffoobar'.decode('iso-8859-1')
+
+    # We need to trick the method under test into believing that a StringIO
+    # instance is a file with an encoding. Since StringIO does not usually have,
+    # an encoding, we'll mock it and add our own encoding, but send the other
+    # methods in use (read and seek) back to the real StringIO object.
+    real_stringio = io.StringIO(bom_prefixed_data)
+    mock_file = MagicMock(spec=io.StringIO)
+    mock_file.read.side_effect = real_stringio.read
+    mock_file.seek.side_effect = real_stringio.seek
+    mock_file.encoding = 'iso-8859-1'
+
+    mock_open = MagicMock(spec=open, return_value=mock_file)
+    with patch.object(fileutils, 'open', mock_open):
+      f = fileutils.open_file(self.fake_path, strip_utf_bom=True)
+      self.assertEqual('foobar', f.read())
+
+  def test_open_file_strips_utf_bom_in_binary(self):
+    bom_prefixed_data = u'\ufefffoobar'.encode('UTF-8')
+    fake_file = io.BytesIO(bom_prefixed_data)
+    mock_open = MagicMock(spec=open, return_value=fake_file)
+    with patch.object(fileutils, 'open', mock_open):
+      f = fileutils.open_file(self.fake_path, mode='rb', strip_utf_bom=True)
+      self.assertEqual(b'foobar', f.read())
+
+  def test_open_file_strip_utf_bom_when_no_bom_in_data(self):
+    no_bom_data = 'This data has no BOM'
+    fake_file = io.StringIO(no_bom_data)
+    mock_open = MagicMock(spec=open, return_value=fake_file)
+
+    with patch.object(fileutils, 'open', mock_open):
+      f = fileutils.open_file(self.fake_path, strip_utf_bom=True)
+      # Since there was no opening BOM, we should be back at the beginning of
+      # the file.
+      self.assertEqual(fake_file.tell(), 0)
+      self.assertEqual(f.read(), no_bom_data)
+
+  @patch.object(fileutils, 'open', new_callable=unittest.mock.mock_open)
+  def test_open_file_exits_on_io_error(self, mock_open):
+    mock_open.side_effect = IOError('Fake IOError')
+    with self.assertRaises(SystemExit) as context:
+      fileutils.open_file(self.fake_path)
+    self.assertEqual(context.exception.code, 6)
+
+  def test_close_file_closes_file_successfully(self):
+    mock_file = MagicMock()
+    self.assertTrue(fileutils.close_file(mock_file))
+    self.assertEqual(mock_file.close.call_count, 1)
+
+  def test_close_file_with_error(self):
+    mock_file = MagicMock()
+    mock_file.close.side_effect = IOError()
+    self.assertFalse(fileutils.close_file(mock_file))
+    self.assertEqual(mock_file.close.call_count, 1)
+
+  @patch.object(fileutils.sys, 'stdin')
+  def test_read_file_from_stdin(self, mock_stdin):
+    mock_stdin.read.return_value = 'some stdin content'
+    self.assertEqual(fileutils.read_file('-'), mock_stdin.read.return_value)
+
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_default_params(self, mock_open_file):
+    fake_content = 'some fake content'
+    mock_open_file.return_value.__enter__().read.return_value = fake_content
+    self.assertEqual(fileutils.read_file(self.fake_path), fake_content)
+    self.assertEqual(mock_open_file.call_args[0][0], self.fake_path)
+    self.assertEqual(mock_open_file.call_args[0][1], 'r')
+    self.assertIsNone(mock_open_file.call_args[1]['newline'])
+
+  @patch.object(fileutils.display, 'print_warning')
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_continues_on_errors_without_displaying(
+      self, mock_open_file, mock_print_warning):
+    mock_open_file.side_effect = IOError()
+    contents = fileutils.read_file(
+        self.fake_path, continue_on_error=True, display_errors=False)
+    self.assertIsNone(contents)
+    self.assertFalse(mock_print_warning.called)
+
+  @patch.object(fileutils.display, 'print_warning')
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_displays_errors(self, mock_open_file, mock_print_warning):
+    mock_open_file.side_effect = IOError()
+    fileutils.read_file(
+        self.fake_path, continue_on_error=True, display_errors=True)
+    self.assertTrue(mock_print_warning.called)
+
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_exits_code_6_when_continue_on_error_is_false(
+      self, mock_open_file):
+    mock_open_file.side_effect = IOError()
+    with self.assertRaises(SystemExit) as context:
+      fileutils.read_file(self.fake_path, continue_on_error=False)
+    self.assertEqual(context.exception.code, 6)
+
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_exits_code_2_on_lookuperror(self, mock_open_file):
+    mock_open_file.return_value.__enter__().read.side_effect = LookupError()
+    with self.assertRaises(SystemExit) as context:
+      fileutils.read_file(self.fake_path)
+    self.assertEqual(context.exception.code, 2)
+
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_exits_code_2_on_unicodeerror(self, mock_open_file):
+    mock_open_file.return_value.__enter__().read.side_effect = UnicodeError()
+    with self.assertRaises(SystemExit) as context:
+      fileutils.read_file(self.fake_path)
+    self.assertEqual(context.exception.code, 2)
+
+  @patch.object(fileutils, '_open_file')
+  def test_read_file_exits_code_2_on_unicodedecodeerror(self, mock_open_file):
+    fake_decode_error = UnicodeDecodeError('fake-encoding', b'fakebytes', 0, 1,
+                                           'testing only')
+    mock_open_file.return_value.__enter__().read.side_effect = fake_decode_error
+    with self.assertRaises(SystemExit) as context:
+      fileutils.read_file(self.fake_path)
+    self.assertEqual(context.exception.code, 2)
+
+  @patch.object(fileutils, '_open_file')
+  def test_write_file_writes_data_to_file(self, mock_open_file):
+    fake_data = 'some fake data'
+    fileutils.write_file(self.fake_path, fake_data)
+    self.assertEqual(mock_open_file.call_args[0][0], self.fake_path)
+    self.assertEqual(mock_open_file.call_args[0][1], 'w')
+
+    opened_file = mock_open_file.return_value.__enter__()
+    self.assertTrue(opened_file.write.called)
+    self.assertEqual(opened_file.write.call_args[0][0], fake_data)
+
+  @patch.object(fileutils.display, 'print_error')
+  @patch.object(fileutils, '_open_file')
+  def test_write_file_continues_on_errors_without_displaying(
+      self, mock_open_file, mock_print_error):
+    mock_open_file.side_effect = IOError()
+    status = fileutils.write_file(
+        self.fake_path,
+        'foo data',
+        continue_on_error=True,
+        display_errors=False)
+    self.assertFalse(status)
+    self.assertFalse(mock_print_error.called)
+
+  @patch.object(fileutils.display, 'print_error')
+  @patch.object(fileutils, '_open_file')
+  def test_write_file_displays_errors(self, mock_open_file, mock_print_error):
+    mock_open_file.side_effect = IOError()
+    fileutils.write_file(
+        self.fake_path, 'foo data', continue_on_error=True, display_errors=True)
+    self.assertTrue(mock_print_error.called)
+
+  @patch.object(fileutils, '_open_file')
+  def test_write_file_exits_code_6_when_continue_on_error_is_false(
+      self, mock_open_file):
+    mock_open_file.side_effect = IOError()
+    with self.assertRaises(SystemExit) as context:
+      fileutils.write_file(self.fake_path, 'foo data', continue_on_error=False)
+    self.assertEqual(context.exception.code, 6)
+
+
+if __name__ == '__main__':
+  unittest.main()