fix: Check if the docstring is defined for modules, classes, class methods, and functions

src/douki/_base/discovery.py

@@ -278,6 +278,12 @@ class _GitIgnoreMatcher:
     """
 
     def __init__(self, root: Path) -> None:
+        """
+        title: Initialize the matcher with a root directory.
+        parameters:
+          root:
+            type: Path
+        """
         self._root: Path = root.resolve()
         self._rules_by_dir: dict[Path, tuple[_GitIgnoreRule, ...]] = {}
 

src/douki/_python/extractor.py

@@ -172,6 +172,9 @@ class _FuncExtractor(ast.NodeVisitor):
     """
 
     def __init__(self) -> None:
+        """
+        title: Initialize the extractor with empty state.
+        """
         self.results: list[FuncInfo] = []
         self.in_class: bool = False
         # Maps class name → full list of attrs (own + inherited)

src/douki/_python/language.py

@@ -21,6 +21,9 @@ class PythonLanguage(BaseLanguage):
     """
 
     def __init__(self) -> None:
+        """
+        title: Initialize the Python language backend.
+        """
         self._config: PythonConfig = PythonConfig()
 
     @property

src/douki/_python/sync.py

@@ -55,6 +55,16 @@ def sync_source(
     if not funcs:
         return source
 
+    # Check for missing docstrings — every function, class, and module
+    # must have a docstring.
+    missing = [f for f in funcs if f.docstring_node is None]
+    if missing:
+        errors = []
+        for f in missing:
+            prefix = '<module>' if f.name == '<module>' else f"'{f.name}'"
+            errors.append(f'- {prefix}: missing docstring')
+        raise DocstringValidationError('\n'.join(errors))
+
     lines = source.splitlines(keepends=True)
     # Process in reverse line order so edits don't shift indices.
     funcs_with_ds = [f for f in funcs if f.docstring_node is not None]