use TypeGuard instead of runtime_checkable

@runtime_checkable doesn't work with trio async file since python3.12
because hasattr in isinstance was replaced with
`inspect.getattr_static()`

Author: tsimoshka

httpx/_content.py

@@ -17,12 +17,12 @@
 from ._multipart import MultipartStream
 from ._types import (
     AsyncByteStream,
-    AsyncFile,
     RequestContent,
     RequestData,
     RequestFiles,
     ResponseContent,
     SyncByteStream,
+    is_async_readable_binary_file,
 )
 from ._utils import peek_filelike_length, primitive_value_to_str
 
@@ -84,7 +84,7 @@ async def __aiter__(self) -> AsyncIterator[bytes]:
             while chunk:
                 yield chunk
                 chunk = await self._stream.aread(self.CHUNK_SIZE)
-        elif isinstance(self._stream, AsyncFile):
+        elif is_async_readable_binary_file(self._stream):
             chunk = await self._stream.read(self.CHUNK_SIZE)
             while chunk:
                 yield chunk
@@ -133,7 +133,7 @@ def encode_content(
         return headers, IteratorByteStream(content)  # type: ignore
 
     elif isinstance(content, AsyncIterable):
-        if isinstance(content, AsyncFile) and (
+        if is_async_readable_binary_file(content) and (
             content_length_or_none := peek_filelike_length(content)
         ):
             headers = {"Content-Length": str(content_length_or_none)}

httpx/_types.py

@@ -2,12 +2,12 @@
 Type definitions for type checking purposes.
 """
 
+import inspect
 from http.cookiejar import CookieJar
 from typing import (
     IO,
     TYPE_CHECKING,
     Any,
-    AnyStr,
     AsyncIterable,
     AsyncIterator,
     Callable,
@@ -21,9 +21,10 @@
     Sequence,
     Tuple,
     Union,
-    runtime_checkable,
 )
 
+from typing_extensions import TypeGuard
+
 if TYPE_CHECKING:  # pragma: no cover
     from ._auth import Auth  # noqa: F401
     from ._config import Proxy, Timeout  # noqa: F401
@@ -117,8 +118,22 @@ async def aclose(self) -> None:
         pass
 
 
-@runtime_checkable
-class AsyncFile(Protocol):
-    async def read(self, size: int = -1) -> AnyStr: ...
+class AsyncReadableBinaryFile(Protocol):
+    async def __aiter__(self) -> AsyncIterator[bytes]: ...
+
+    async def read(self, size: int = -1) -> bytes: ...
 
     def fileno(self) -> int: ...
+
+
+def is_async_readable_binary_file(fp: Any) -> TypeGuard[AsyncReadableBinaryFile]:
+    return (
+        isinstance(fp, AsyncIterable)
+        and hasattr(fp, "read")
+        and inspect.iscoroutinefunction(fp.read)
+        and hasattr(fp, "fileno")
+        and callable(fp.fileno)
+        and not inspect.iscoroutinefunction(fp.fileno)
+        and hasattr(fp, "mode")
+        and "b" in fp.mode
+    )

tests/test_content.py

@@ -8,7 +8,7 @@
 
 import httpx
 from httpx._content import AsyncIteratorByteStream
-from httpx._types import AsyncFile
+from httpx._types import AsyncReadableBinaryFile, is_async_readable_binary_file
 
 method = "POST"
 url = "https://www.example.com"
@@ -537,7 +537,9 @@ def echo_request_content(request: httpx.Request) -> httpx.Response:
     to_upload = tmp_path / "upload.txt"
     to_upload.write_bytes(content_bytes)
 
-    async def checks(client: httpx.AsyncClient, async_file: AsyncFile) -> None:
+    async def checks(
+        client: httpx.AsyncClient, async_file: AsyncReadableBinaryFile
+    ) -> None:
         read_called = 0
         fileno_called = 0
         original_read = async_file.read
@@ -572,7 +574,7 @@ def mock_fileno(*args):
             transport=httpx.MockTransport(echo_request_content)
         ) as client,
     ):
-        assert isinstance(async_file, AsyncFile)
+        assert is_async_readable_binary_file(async_file)
         await checks(client, async_file)
 
     if anyio_backend != "trio":  # aiofiles doesn't work with trio
@@ -582,5 +584,5 @@ def mock_fileno(*args):
                 transport=httpx.MockTransport(echo_request_content)
             ) as client,
         ):
-            assert isinstance(aio_file, AsyncFile)
+            assert is_async_readable_binary_file(aio_file)
             await checks(client, aio_file)