refactor: use _init_subclass to register docstring parsers

arger/docstring.py

@@ -1,4 +1,3 @@
-import functools
 import inspect
 import re
 import typing as tp
@@ -41,7 +40,22 @@ class DocstringParser:
     section_ptrn: tp.Pattern
     param_ptrn: tp.Pattern
 
-    def parse(self, doc: str) -> DocstringTp:
+    _parsers: tp.List['DocstringParser'] = []
+
+    def __init_subclass__(cls, **_):
+        # Cache costly init phase per session.
+        cls._parsers.append(cls())
+
+    @classmethod
+    def parse(cls, func: tp.Optional[tp.Callable]) -> DocstringTp:
+        doc = (inspect.getdoc(func) or '') if func else ''
+        if doc:
+            for parser in cls._parsers:
+                if parser.matches(doc):
+                    return parser._parse(doc)
+        return DocstringTp(description=doc, epilog='', params={})
+
+    def _parse(self, doc: str) -> DocstringTp:
         raise NotImplementedError
 
     def matches(self, doc: str) -> bool:
@@ -81,7 +95,7 @@ def parse_params(self, params: str) -> tp.Dict[str, ParamDocTp]:
             for param, tphint, doc in docs
         }
 
-    def parse(self, doc: str) -> DocstringTp:
+    def _parse(self, doc: str) -> DocstringTp:
         desc, _, params = self.pattern.split(doc, maxsplit=1)
         other_sect, params = self.get_rest_of_section(params)
         return DocstringTp(desc.strip(), other_sect, params=self.parse_params(params))
@@ -121,7 +135,7 @@ def parse_doc(self, line: str, params: tp.Dict[str, ParamDocTp]):
                 type_hint = parts[0].strip()
             params[param] = ParamDocTp.init(type_hint, doc)
 
-    def parse(self, doc: str) -> DocstringTp:
+    def _parse(self, doc: str) -> DocstringTp:
         lines = self.pattern.split(doc)
         long_desc = lines.pop(0)
         epilog = ''
@@ -133,18 +147,3 @@ def parse(self, doc: str) -> DocstringTp:
             self.parse_doc(sections[0], params)
 
         return DocstringTp(long_desc.strip(), epilog, params)
-
-
-@functools.lru_cache(None)
-def _docstring_parsers():
-    """Cache costly init phase per session."""
-    return [NumpyDocParser(), GoogleDocParser(), RstDocParser()]
-
-
-def parse_docstring(func: tp.Optional[tp.Callable]) -> DocstringTp:
-    doc = (inspect.getdoc(func) or '') if func else ''
-    if doc:
-        for parser in _docstring_parsers():
-            if parser.matches(doc):
-                return parser.parse(doc)
-    return DocstringTp(description=doc, epilog='', params={})

arger/main.py

@@ -8,7 +8,7 @@
 from typing import Any, Tuple, Union
 
 from arger import typing_utils as tp_utils
-from arger.docstring import DocstringTp, ParamDocTp, parse_docstring
+from arger.docstring import DocstringParser, DocstringTp, ParamDocTp
 
 CMD_TITLE = "commands"
 LEVEL = '__level__'
@@ -170,7 +170,7 @@ def __init__(
         self.sub_parser_action: tp.Optional[ap._SubParsersAction] = None
 
         self.args: tp.Dict[str, Argument] = OrderedDict()
-        docstr = parse_docstring(func) if _doc_str is None else _doc_str
+        docstr = DocstringParser.parse(func) if _doc_str is None else _doc_str
         kwargs.setdefault("description", docstr.description)
         kwargs.setdefault("epilog", docstr.epilog)
 
@@ -201,7 +201,7 @@ def _add_arguments(self, func: tp.Callable, docstr: DocstringTp, level: int):
             self._add_arg(arg)
 
     def _add_arg(self, arg: Argument):
-        self.add_argument(*arg.flags, **arg.kwargs)
+        return self.add_argument(*arg.flags, **arg.kwargs)
 
     def run(self, *args: str, capture_sys=True) -> ap.Namespace:
         """Parse cli and dispatch functions.
@@ -244,7 +244,7 @@ def add_cmd(self, func: tp.Callable) -> ap.ArgumentParser:
         if not self.sub_parser_action:
             self.sub_parser_action = self.add_subparsers(title=CMD_TITLE)
 
-        docstr = parse_docstring(func)
+        docstr = DocstringParser.parse(func)
         return self.sub_parser_action.add_parser(
             name=func.__name__,
             help=docstr.description,

tests/test_docstrings_parser.py

@@ -1,6 +1,6 @@
 import pytest
 
-from arger.docstring import ParamDocTp, parse_docstring
+from arger.docstring import DocstringParser, ParamDocTp
 
 
 def func_numpy():
@@ -69,7 +69,7 @@ def func_rst():
     ],
 )
 def test_docstring_parser(fn):
-    result = parse_docstring(fn)
+    result = DocstringParser.parse(fn)
     assert result.description == "Summary line.\n\nExtended description of function."
     assert list(result.params) == ['arg1', 'arg2', 'arg3', 'arg4']
     assert list(result.params.values()) == [