Fix regex to correctly capture default values in environment variable replacement

[horihiro]

Fix #37

[Copilot]

Pull Request Overview

This PR fixes the regex pattern used for capturing default values in environment variable replacement and adds a comprehensive suite of tests for various default value scenarios.

• Updated the regex to restrict the default value pattern and added escaping for special characters.
• Added new test cases for environment variable default values including nested defaults and special characters (asterisk, plus, question mark, and right brace).

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/tests/environment_variable_evaluation/test_environment_variables_braces.py	Added tests for multiple default scenarios including nested defaults and special characters
src/pycomposefile/compose_element/compose_datatype_transformer.py	Updated regex and escape handling for default values in environment variable replacement

Comments suppressed due to low confidence (1)

src/tests/environment_variable_evaluation/test_environment_variables_braces.py:30

• [nitpick] It may be helpful to add an inline comment clarifying the expected behavior for the nested default scenario to assist future maintainers.

def test_uppercase_with_nested_default_when_unset_in_string_value(self):

[Copilot]

Consider using re.escape(matches[0]) instead of a custom regex to escape special characters, as it improves readability and reduces the risk of missing additional special characters.

Suggested change

	escaped = re.sub(r"([*+?{}])", r"\\\1", matches[0]) # escape special characters
	escaped = re.escape(matches[0]) # escape special characters