Type Traversable/list_traverse() better, make IterablleObj a protocol

4 files changed, 22 insertions, 19 deletions

diff --git a/git/objects/util.py b/git/objects/util.py
index fce62af2..bc6cdf8f 100644
--- a/git/objects/util.py
+++ b/git/objects/util.py
@@ -23,7 +23,7 @@ from datetime import datetime, timedelta, tzinfo
 from typing import (Any, Callable, Deque, Iterator, NamedTuple, overload, Sequence,
                     TYPE_CHECKING, Tuple, Type, TypeVar, Union, cast)
 
-from git.types import Literal
+from git.types import Literal, TypeGuard
 
 if TYPE_CHECKING:
     from io import BytesIO, StringIO
@@ -306,24 +306,20 @@ class Traversable(object):
         """
         raise NotImplementedError("To be implemented in subclass")
 
-    def list_traverse(self, *args: Any, **kwargs: Any
-                      ) -> Union[IterableList['TraversableIterableObj'],
-                                 IterableList[Tuple[Union[None, 'TraversableIterableObj'], 'TraversableIterableObj']]]:
+    def list_traverse(self, *args: Any, **kwargs: Any) -> IterableList['TraversableIterableObj']:
         """
         :return: IterableList with the results of the traversal as produced by
             traverse()
             List objects must be IterableObj and Traversable e.g. Commit, Submodule"""
 
-        out: Union[IterableList['TraversableIterableObj'],
-                   IterableList[Tuple[Union[None, 'TraversableIterableObj'], 'TraversableIterableObj']]]
-
-        # def is_TraversableIterableObj(inp: Union['Traversable', IterableObj]) -> TypeGuard['TraversableIterableObj']:
-        #     return isinstance(self, TraversableIterableObj)
-        # assert is_TraversableIterableObj(self), f"{type(self)}"
-
-        self = cast('TraversableIterableObj', self)
-        out = IterableList(self._id_attribute_)
-        out.extend(self.traverse(*args, **kwargs))  # type: ignore
+        def is_TraversableIterableObj(inp: 'Traversable') -> TypeGuard['TraversableIterableObj']:
+            # return isinstance(self, TraversableIterableObj)
+            # Can it be anythin else?
+            return isinstance(self, Traversable)
+        
+        assert is_TraversableIterableObj(self), f"{type(self)}"
+        out: IterableList['TraversableIterableObj'] = IterableList(self._id_attribute_)
+        out.extend(self.traverse(*args, **kwargs))
         return out
 
     def traverse(self,
diff --git a/git/remote.py b/git/remote.py
index a036446e..0ef54ea7 100644
--- a/git/remote.py
+++ b/git/remote.py
@@ -128,6 +128,7 @@ class PushInfo(IterableObj, object):
         info.summary    # summary line providing human readable english text about the push
         """
     __slots__ = ('local_ref', 'remote_ref_string', 'flags', '_old_commit_sha', '_remote', 'summary')
+    _id_attribute_ = 'pushinfo'
 
     NEW_TAG, NEW_HEAD, NO_MATCH, REJECTED, REMOTE_REJECTED, REMOTE_FAILURE, DELETED, \
         FORCED_UPDATE, FAST_FORWARD, UP_TO_DATE, ERROR = [1 << x for x in range(11)]
@@ -242,6 +243,7 @@ class FetchInfo(IterableObj, object):
      info.remote_ref_path # The path from which we fetched on the remote. It's the remote's version of our info.ref
     """
     __slots__ = ('ref', 'old_commit', 'flags', 'note', 'remote_ref_path')
+    _id_attribute_ = 'fetchinfo'
 
     NEW_TAG, NEW_HEAD, HEAD_UPTODATE, TAG_UPDATE, REJECTED, FORCED_UPDATE, \
         FAST_FORWARD, ERROR = [1 << x for x in range(8)]
diff --git a/git/types.py b/git/types.py
index ea91d038..ad9bed16 100644
--- a/git/types.py
+++ b/git/types.py
@@ -6,6 +6,11 @@ import os
 import sys
 from typing import Dict, Union, Any, TYPE_CHECKING
 
+if sys.version_info[:2] >= (3, 7):
+    from typing import Protocol  # noqa: F401
+else:
+    from typing_extensions import Protocol  # noqa: F401
+
 if sys.version_info[:2] >= (3, 8):
     from typing import Final, Literal, SupportsIndex, TypedDict  # noqa: F401
 else:
@@ -18,7 +23,6 @@ else:
 
 
 if sys.version_info[:2] < (3, 9):
-    # Python >= 3.6, < 3.9
     PathLike = Union[str, os.PathLike]
 elif sys.version_info[:2] >= (3, 9):
     # os.PathLike only becomes subscriptable from Python 3.9 onwards
diff --git a/git/util.py b/git/util.py
index 057d7478..ebb119b9 100644
--- a/git/util.py
+++ b/git/util.py
@@ -27,7 +27,7 @@ import warnings
 
 # typing ---------------------------------------------------------
 
-from typing import (Any, AnyStr, BinaryIO, Callable, Dict, Generator, IO, Iterable as typIter, Iterator, List,
+from typing import (Any, AnyStr, BinaryIO, Callable, Dict, Generator, IO, Iterator, List,
                     Optional, Pattern, Sequence, Tuple, TypeVar, Union, cast, TYPE_CHECKING, overload)
 
 import pathlib
@@ -37,9 +37,10 @@ if TYPE_CHECKING:
     from git.repo.base import Repo
     from git.config import GitConfigParser, SectionConstraint
 
-from .types import PathLike, Literal, SupportsIndex, HSH_TD, Total_TD, Files_TD
+from .types import (Literal, Protocol, SupportsIndex,                    # because behind py version guards
+                    PathLike, HSH_TD, Total_TD, Files_TD)                # aliases
 
-T_IterableObj = TypeVar('T_IterableObj', bound=Union['IterableObj', typIter], covariant=True)
+T_IterableObj = TypeVar('T_IterableObj', bound='IterableObj', covariant=True)
 
 # So IterableList[Head] is subtype of IterableList[IterableObj]
 # ---------------------------------------------------------------------
@@ -1065,7 +1066,7 @@ class Iterable(object):
         raise NotImplementedError("To be implemented by Subclass")
 
 
-class IterableObj():
+class IterableObj(Protocol):
     """Defines an interface for iterable items which is to assure a uniform
     way to retrieve and iterate items within the git repository