TYPING Remove uses of abc.register

Mypy doesn't understand `@abc.register`:
python/mypy#2922
so we should subclass the abc directly instead. This requires using a
custom metaclass which is simultaneously a subclass of JsProxy and ABCMeta.

src/py/_pyodide/_core_docs.py

@@ -1,5 +1,6 @@
 import os
 import sys
+from abc import ABCMeta
 from collections.abc import (
  AsyncIterator,
  Awaitable,
@@ -10,12 +11,13 @@
  KeysView,
  Mapping,
  MutableMapping,
+ MutableSequence,
  Sequence,
  ValuesView,
 )
 from functools import reduce
 from types import TracebackType
-from typing import IO, Any, Generic, TypeVar, overload
+from typing import IO, Any, Generic, Protocol, TypeVar, overload
 
 from .docs_argspec import docs_argspec
 
@@ -87,6 +89,10 @@ def __subclasscheck__(cls, subclass):
  return any(cls_flag & subclass_flags == cls_flag for cls_flag in cls_flags)
 
 
+class _ABCMeta(_JsProxyMetaClass, ABCMeta):
+ pass
+
+
 # We want to raise an error if someone tries to instantiate JsProxy directly
 # since it doesn't mean anything. But we have a few reasons to do so internally.
 # So we raise an error unless this private token is passed as an argument.
@@ -790,15 +796,31 @@ def __call__(self):
  pass
 
 
-class JsArray(JsIterable[T], Generic[T]):
+class JsArray(JsIterable[T], Generic[T], MutableSequence[T], metaclass=_ABCMeta):
  """A JsProxy of an :js:class:`Array`, :js:class:`NodeList`, or :js:class:`TypedArray`"""
 
  _js_type_flags = ["IS_ARRAY", "IS_NODE_LIST", "IS_TYPEDARRAY"]
 
- def __getitem__(self, idx: int | slice) -> T:
+ @overload
+ def __getitem__(self, idx: int) -> T:
+ ...
+
+ @overload
+ def __getitem__(self, idx: slice) -> "JsArray[T]":
+ ...
+
+ def __getitem__(self, idx):
  raise NotImplementedError
 
- def __setitem__(self, idx: int | slice, value: T) -> None:
+ @overload
+ def __setitem__(self, idx: int, value: T) -> None:
+ ...
+
+ @overload
+ def __setitem__(self, idx: slice, value: Iterable[T]) -> None:
+ ...
+
+ def __setitem__(self, idx, value):
  pass
 
  def __delitem__(self, idx: int | slice) -> None:
@@ -872,8 +894,7 @@ def subarray(
  buffer: JsBuffer
 
 
-@Mapping.register
-class JsMap(JsIterable[KT], Generic[KT, VTco]):
+class JsMap(JsIterable[KT], Generic[KT, VTco], Mapping[KT, VTco], metaclass=_ABCMeta):
  """A JavaScript Map
 
  To be considered a map, a JavaScript object must have a ``get`` method, it
@@ -889,7 +910,7 @@ def __getitem__(self, idx: KT) -> VTco:
  def __len__(self) -> int:
  return 0
 
- def __contains__(self, idx: KT) -> bool:
+ def __contains__(self, idx: object) -> bool:
  raise NotImplementedError
 
  def keys(self) -> KeysView[KT]:
@@ -918,8 +939,17 @@ def get(self, key: KT, default: Any = None, /) -> VTco:
  raise NotImplementedError
 
 
-@MutableMapping.register
-class JsMutableMap(JsMap[KT, VT], Generic[KT, VT]):
+class _SupportsKeysAndGetItem(Protocol[KT, VTco]):
+ def keys(self) -> Iterable[KT]:
+ ...
+
+ def __getitem__(self, __key: KT) -> VTco:
+ ...
+
+
+class JsMutableMap(
+ JsMap[KT, VT], Generic[KT, VT], MutableMapping[KT, VT], metaclass=_ABCMeta
+):
  """A JavaScript mutable map
 
  To be considered a mutable map, a JavaScript object must have a ``get``
@@ -964,7 +994,7 @@ def clear(self) -> None:
  """Empty out the map entirely."""
 
  @overload
- def update(self, __m: Mapping[KT, VT], **kwargs: VT) -> None:
+ def update(self, __m: _SupportsKeysAndGetItem[KT, VT], **kwargs: VT) -> None:
  ...
 
  @overload