Implement Array protocol in src/graphql_relay/connection/arrayconnection.py

Author: Mark Edwards

Diff for: pyproject.toml

@@ -31,6 +31,7 @@ packages = [
 [tool.poetry.dependencies]
 python = "^3.6"
 graphql-core = "^3.0"
+typing-extensions = { version = "^3.6.2", python = "<3.8" }
 
 [tool.poetry.dev-dependencies]
 pytest = "^5.3"

Diff for: setup.py

@@ -29,7 +29,10 @@
         "Programming Language :: Python :: 3.8",
         "Programming Language :: Python :: Implementation :: PyPy",
     ],
-    install_requires=["graphql-core>=3.0.0"],
+    install_requires=[
+        "graphql-core>=3.0.0",
+        "typing-extensions>=3.6.2,<4; python_version < '3.8'",
+    ],
     python_requires=">=3.6,<4",
     packages=find_packages("src"),
     package_dir={"": "src"},

Diff for: src/graphql_relay/connection/arrayconnection.py

@@ -1,6 +1,10 @@
 import binascii
 import warnings
-from typing import Any, Optional, Sequence
+from typing import Any, Iterator, Optional, overload, Sequence, Sized, Union
+try:
+    from typing import Protocol
+except ImportError:
+    from typing_extensions import Protocol  # type: ignore
 
 from ..utils.base64 import base64, unbase64
 from .connectiontypes import (
@@ -21,8 +25,17 @@
 ]
 
 
+class Sliceable(Protocol):
+    def __getitem__(self, index: slice) -> Any: ...
+    def __iter__(self) -> Iterator: ...
+
+
+class SizedSliceable(Sliceable, Protocol):
+    def __len__(self) -> int: ...
+
+
 def connection_from_array(
-    data: Sequence,
+    data: SizedSliceable,
     args: ConnectionArguments = None,
     connection_type: Any = Connection,
     edge_type: Any = Edge,
@@ -78,8 +91,35 @@ def connection_from_list(
     )
 
 
+@overload
+def connection_from_array_slice(
+    array_slice: Sliceable,
+    *,
+    args: ConnectionArguments = None,
+    slice_start: int = 0,
+    array_length: int = None,
+    array_slice_length: int,
+    connection_type: Any = Connection,
+    edge_type: Any = Edge,
+    page_info_type: Any = PageInfo,
+) -> Connection: ...
+
+
+@overload
+def connection_from_array_slice(
+    array_slice: SizedSliceable,
+    args: ConnectionArguments = None,
+    slice_start: int = 0,
+    array_length: int = None,
+    array_slice_length: int = None,
+    connection_type: Any = Connection,
+    edge_type: Any = Edge,
+    page_info_type: Any = PageInfo,
+) -> Connection: ...
+
+
 def connection_from_array_slice(
-    array_slice: Sequence,
+    array_slice: Union[Sliceable, SizedSliceable],
     args: ConnectionArguments = None,
     slice_start: int = 0,
     array_length: int = None,
@@ -112,6 +152,7 @@ def connection_from_array_slice(
     first = args.get("first")
     last = args.get("last")
     if array_slice_length is None:
+        assert isinstance(array_slice, Sized)
         array_slice_length = len(array_slice)
     slice_end = slice_start + array_slice_length
     if array_length is None: