fix: handle identifier with regex characters

Provides a test for and the solution to GitHub
issue #242. Namely, an identifier which contains
regex characters (e.g. "[TODO]") is properly
handled by having the parser look for literal
"[" and "]" characters rather than treating those
characters as part of a regex pattern. The word
boundary regex pattern '\b' does NOT properly
handle this, so a slightly different pattern is
used to identify the boundary.

tests/test_new.diff

@@ -58,7 +58,7 @@ index 0000000..525e25d
 +    # TODO: Come up with a more imaginative greeting
 +    print('Hello world')
 +
-+    # TODO: Do more stuff
++    # [TODO]: Do more stuff
 +    #  This function should probably do something more interesting
 +    #  labels: help wanted
 +

tests/test_process_diff.py

@@ -78,7 +78,7 @@ class IssueUrlInsertionTest(unittest.TestCase):
                      "Skipping because 'SKIP_PROCESS_DIFF_TEST' is 'true'")
     def test_url_insertion(self):
         self._setUp(['test_new.diff'])
-        self._standardTest(80)
+        self._standardTest(79)
 
     def test_line_numbering_with_deletions(self):
         self._setUp(['test_new_py.diff', 'test_edit_py.diff'])

tests/test_todo_parser.py

@@ -45,7 +45,7 @@ class NewIssueTest(unittest.TestCase):
 
     def test_python_issues(self):
         # Includes 4 tests for Starlark.
-        self.assertEqual(count_issues_for_file_type(self.raw_issues, 'python'), 8)
+        self.assertEqual(count_issues_for_file_type(self.raw_issues, 'python'), 7)
 
     def test_yaml_issues(self):
         self.assertEqual(count_issues_for_file_type(self.raw_issues, 'yaml'), 2)
@@ -80,7 +80,7 @@ class NewIssueTest(unittest.TestCase):
         self.assertEqual(count_issues_for_file_type(self.raw_issues, 'julia'), 2)
 
     def test_starlark_issues(self):
-        self.assertEqual(count_issues_for_file_type(self.raw_issues, 'python'), 8)
+        self.assertEqual(count_issues_for_file_type(self.raw_issues, 'python'), 7)
 
     def test_autohotkey_issues(self):
         self.assertEqual(count_issues_for_file_type(self.raw_issues, 'autohotkey'), 1)
@@ -133,7 +133,9 @@ class CustomOptionsTest(unittest.TestCase):
     def setUp(self):
         parser = TodoParser(options={"identifiers":
                                      [{"name": "FIX", "labels": []},
-                                      {"name": "TODO", "labels": []}]})
+                                      {"name": "[TODO]", "labels": []},
+                                      {"name": "TODO", "labels": []}
+                                      ]})
         self.raw_issues = []
         with open('syntax.json', 'r') as syntax_json:
             parser.syntax_dict = json.load(syntax_json)
@@ -157,6 +159,23 @@ class CustomOptionsTest(unittest.TestCase):
         self.assertEqual(len(matching_issues), 0,
                          msg=print_unexpected_issues(matching_issues))
 
+    # See GitHub issue #242
+    def test_regex_identifier_chars(self):
+        """
+        Verify that the presence of regex characters in the identifier
+        doesn't confuse the parser
+
+        An identifier such as "[TODO]" should be matched literally, not treating
+        the "[" and "]" characters as part of a regular expression pattern.
+        """
+        matching_issues = get_issues_for_fields(self.raw_issues,
+                                                {
+                                                    "file_name": "example_file.py",
+                                                    "identifier": "[TODO]"
+                                                })
+        self.assertEqual(len(matching_issues), 1,
+                         msg=print_unexpected_issues(matching_issues))
+
     # See GitHub issue #235
     @unittest.expectedFailure
     def test_multiple_identifiers(self):