Typing fixes in file_handler: avoid cast()

Author: ogenstad

infrahub_sdk/file_handler.py

@@ -3,10 +3,11 @@
 from dataclasses import dataclass
 from io import BytesIO
 from pathlib import Path
-from typing import TYPE_CHECKING, BinaryIO, cast, overload
+from typing import TYPE_CHECKING, BinaryIO, overload
 
 import anyio
 import httpx
+from anyio.to_thread import run_sync as run_sync_in_thread
 
 from .exceptions import AuthenticationError, NodeNotFoundError, ServerNotReachableError
 
@@ -21,6 +22,17 @@ class PreparedFile:
     should_close: bool
 
 
+def _open_binary(path: Path) -> BinaryIO:
+    """Open a file in binary read mode.
+
+    Wrapper exists to pin the return type to BinaryIO when called via
+    ``run_sync_in_thread``: the overload resolution on ``Path.open``'s mode arg
+    is lost through the indirection and would otherwise widen to a union of all
+    open() return types.
+    """
+    return path.open("rb")
+
+
 class FileHandlerBase:
     """Base class for file handling operations.
 
@@ -57,11 +69,11 @@ async def prepare_upload(content: bytes | Path | BinaryIO | None, name: str | No
         if isinstance(content, Path):
             # Open file in thread pool to avoid blocking the event loop
             # Returns a sync file handle that httpx can stream from in chunks
-            file_obj = await anyio.to_thread.run_sync(content.open, "rb")
-            return PreparedFile(file_object=cast("BinaryIO", file_obj), filename=filename, should_close=True)
+            file_obj = await run_sync_in_thread(_open_binary, content)
+            return PreparedFile(file_object=file_obj, filename=filename, should_close=True)
 
         # At this point, content must be a BinaryIO (file-like object)
-        return PreparedFile(file_object=cast("BinaryIO", content), filename=filename, should_close=False)
+        return PreparedFile(file_object=content, filename=filename, should_close=False)
 
     @staticmethod
     def prepare_upload_sync(content: bytes | Path | BinaryIO | None, name: str | None = None) -> PreparedFile:
@@ -92,7 +104,7 @@ def prepare_upload_sync(content: bytes | Path | BinaryIO | None, name: str | Non
             return PreparedFile(file_object=content.open("rb"), filename=filename, should_close=True)
 
         # At this point, content must be a BinaryIO (file-like object)
-        return PreparedFile(file_object=cast("BinaryIO", content), filename=filename, should_close=False)
+        return PreparedFile(file_object=content, filename=filename, should_close=False)
 
     @staticmethod
     def handle_error_response(exc: httpx.HTTPStatusError) -> None:

pyproject.toml

@@ -143,10 +143,10 @@ include = ["infrahub_sdk/checks.py"]
 invalid-await = "ignore" # 1 violation
 
 [[tool.ty.overrides]]
-include = ["infrahub_sdk/file_handler.py", "infrahub_sdk/utils.py"]
+include = ["infrahub_sdk/utils.py"]
 
 [tool.ty.overrides.rules]
-unresolved-attribute = "ignore" # 5 violations total (1 in file_handler.py, 4 in utils.py)
+unresolved-attribute = "ignore" # 4 violations in utils.py
 
 [[tool.ty.overrides]]
 include = ["infrahub_sdk/transfer/**"]

tests/unit/sdk/test_file_handler.py

@@ -3,7 +3,7 @@
 import tempfile
 from io import BytesIO
 from pathlib import Path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, BinaryIO
 
 import anyio
 import httpx
@@ -22,6 +22,15 @@
 NODE_ID = "test-node-123"
 
 
+def _open_binary_handle(path: str) -> BinaryIO:
+    """Sync helper to open a file in binary read mode.
+
+    Defined as a sync function so ruff's ASYNC* rules don't apply when called from async tests.
+    The handle is the realistic non-BytesIO BinaryIO that production callers pass to ``prepare_upload``.
+    """
+    return Path(path).open("rb")
+
+
 async def test_prepare_upload_with_bytes() -> None:
     """Test preparing upload with bytes content (async)."""
     content = b"test file content"
@@ -85,6 +94,26 @@ async def test_prepare_upload_with_binary_io() -> None:
     assert prepared.should_close is False
 
 
+async def test_prepare_upload_with_open_file() -> None:
+    """Test preparing upload with a real file handle (not BytesIO) — async.
+
+    Locks in BinaryIO branch behaviour for callers passing the result of opening a real
+    file, not just ``BytesIO``. Guards against narrowing the dispatch to a too-specific
+    type.
+    """
+    with tempfile.NamedTemporaryFile(suffix=".txt") as tmp:
+        tmp.write(b"content from open file")
+        tmp.flush()
+
+        with _open_binary_handle(tmp.name) as file_handle:
+            prepared = await FileHandlerBase.prepare_upload(content=file_handle, name="from_open.bin")
+
+            assert prepared.file_object is file_handle
+            assert prepared.filename == "from_open.bin"
+            assert prepared.should_close is False
+            assert prepared.file_object.read() == b"content from open file"
+
+
 async def test_prepare_upload_with_none() -> None:
     """Test preparing upload with None content (async)."""
     prepared = await FileHandlerBase.prepare_upload(content=None)
@@ -157,6 +186,26 @@ def test_prepare_upload_sync_with_binary_io() -> None:
     assert prepared.should_close is False
 
 
+def test_prepare_upload_sync_with_open_file() -> None:
+    """Test preparing upload with a real file handle (not BytesIO) — sync.
+
+    Locks in BinaryIO branch behaviour for callers passing the result of opening a real
+    file, not just ``BytesIO``. Guards against narrowing the dispatch to a too-specific
+    type.
+    """
+    with tempfile.NamedTemporaryFile(suffix=".txt") as tmp:
+        tmp.write(b"content from open file")
+        tmp.flush()
+
+        with _open_binary_handle(tmp.name) as file_handle:
+            prepared = FileHandlerBase.prepare_upload_sync(content=file_handle, name="from_open.bin")
+
+            assert prepared.file_object is file_handle
+            assert prepared.filename == "from_open.bin"
+            assert prepared.should_close is False
+            assert prepared.file_object.read() == b"content from open file"
+
+
 def test_prepare_upload_sync_with_none() -> None:
     """Test preparing upload with None content (sync)."""
     prepared = FileHandlerBase.prepare_upload_sync(content=None)