Add default option to RegexSource (#1980)

backend/src/hatchling/version/core.py

@@ -18,8 +18,10 @@ def __init__(self, root: str, relative_path: str) -> None:
         self.__path = os.path.normpath(os.path.join(root, relative_path))
         self.__cached_read_data: tuple | None = None
 
-    def read(self, *, pattern: str | bool) -> str:
+    def read(self, *, pattern: str | bool, default: str | None = None) -> str:
         if not os.path.isfile(self.__path):
+            if default is not None:
+                return default
             message = f'file does not exist: {self.__relative_path}'
             raise OSError(message)
 

backend/src/hatchling/version/source/regex.py

@@ -20,8 +20,13 @@ def get_version_data(self) -> dict:
             message = 'option `pattern` must be a string'
             raise TypeError(message)
 
+        default = self.config.get('default')
+        if default is not None and not isinstance(default, str):
+            message = 'option `default` must be a string'
+            raise TypeError(message)
+
         version_file = VersionFile(self.root, relative_path)
-        version = version_file.read(pattern=pattern)
+        version = version_file.read(pattern=pattern, default=default)
 
         return {'version': version, 'version_file': version_file}
 

docs/plugins/version-source/regex.md

@@ -23,3 +23,4 @@ source = "regex"
 | --- | --- |
 | `path` (required) | A relative path to a file containing the project's version |
 | `pattern` | A regular expression that has a named group called `version` that represents the version. The default pattern looks for a variable named `__version__` or `VERSION` that is set to a string containing the version, optionally prefixed with the lowercase letter `v`. |
+| `default` | A value used as the version if the file at `path` does not exist. |

tests/backend/version/source/test_regex.py

@@ -117,3 +117,28 @@ def foo():
     with temp_dir.as_cwd():
         source.set_version('foo', source.get_version_data())
         assert source.get_version_data()['version'] == 'foo'
+
+
+@pytest.mark.parametrize(
+    ('file_contents', 'default', 'expected_version'),
+    [
+        ('1.2.3', '0.0.0', '1.2.3'),
+        ('1.2.3', '0.0.1', '1.2.3'),
+        (None, '0.dev', '0.dev'),
+        (None, '9.9.9', '9.9.9'),
+    ],
+)
+def test_with_default_value(temp_dir, file_contents, default, expected_version):
+    source = RegexSource(
+        str(temp_dir),
+        {'path': 'x/y', 'pattern': '^(?P<version>.+)$', 'default': default},
+    )
+
+    file_path = temp_dir / 'x' / 'y'
+    file_path.ensure_parent_dir_exists()
+
+    if file_contents is not None:
+        file_path.write_text(file_contents)
+
+    with temp_dir.as_cwd():
+        assert source.get_version_data()['version'] == expected_version