Detect blocking calls in coroutines using BlockBuster

cbornet · cbornet · commit a6d039475030 · 2025-02-19T18:01:53.000+01:00
diff --git a/.gitignore b/.gitignore
@@ -11,3 +11,4 @@ venv*/
 .python-version
 build/
 dist/
+.idea/
diff --git a/requirements.txt b/requirements.txt
@@ -12,6 +12,7 @@ types-PyYAML==6.0.12.20241230
 types-dataclasses==0.6.6
 pytest==8.3.4
 trio==0.28.0
+blockbuster==1.5.13
 
 # Documentation
 black==25.1.0
diff --git a/starlette/datastructures.py b/starlette/datastructures.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import sys
 import typing
 from shlex import shlex
 from urllib.parse import SplitResult, parse_qsl, urlencode, urlsplit
@@ -438,7 +439,7 @@ async def write(self, data: bytes) -> None:
         if self.size is not None:
             self.size += len(data)
 
-        if self._in_memory:
+        if self._in_memory and self.file.tell() + len(data) <= getattr(self.file, "_max_size", sys.maxsize):
             self.file.write(data)
         else:
             await run_in_threadpool(self.file.write, data)
diff --git a/starlette/middleware/errors.py b/starlette/middleware/errors.py
@@ -6,6 +6,8 @@
 import traceback
 import typing
 
+import anyio
+
 from starlette._utils import is_async_callable
 from starlette.concurrency import run_in_threadpool
 from starlette.requests import Request
@@ -167,7 +169,7 @@ async def _send(message: Message) -> None:
             request = Request(scope)
             if self.debug:
                 # In debug mode, return traceback responses.
-                response = self.debug_response(request, exc)
+                response = await anyio.to_thread.run_sync(self.debug_response, request, exc)
             elif self.handler is None:
                 # Use our default 500 error handler.
                 response = self.error_response(request, exc)
diff --git a/starlette/testclient.py b/starlette/testclient.py
@@ -288,7 +288,7 @@ async def receive() -> Message:
                     await response_complete.wait()
                 return {"type": "http.disconnect"}
 
-            body = request.read()
+            body = await anyio.to_thread.run_sync(request.read)
             if isinstance(body, str):
                 body_bytes: bytes = body.encode("utf-8")  # pragma: no cover
             elif body is None:
diff --git a/tests/conftest.py b/tests/conftest.py
@@ -1,14 +1,23 @@
 from __future__ import annotations
 
 import functools
+from collections.abc import Iterator
 from typing import Any, Literal
 
 import pytest
+from blockbuster import blockbuster_ctx
 
 from starlette.testclient import TestClient
 from tests.types import TestClientFactory
 
 
+@pytest.fixture(autouse=True)
+def blockbuster() -> Iterator[None]:
+    with blockbuster_ctx("starlette") as bb:
+        bb.functions["os.stat"].can_block_in("/mimetypes.py", "init")
+        yield
+
+
 @pytest.fixture
 def test_client_factory(
     anyio_backend_name: Literal["asyncio", "trio"],
diff --git a/tests/middleware/test_base.py b/tests/middleware/test_base.py
@@ -466,9 +466,9 @@ async def cancel_on_disconnect(
             # before we start returning the body
             await task_group.start(cancel_on_disconnect)
 
-            # A timeout is set for 0.1 second in order to ensure that
+            # A timeout is set for 0.2 second in order to ensure that
             # we never deadlock the test run in an infinite loop
-            with anyio.move_on_after(0.1):
+            with anyio.move_on_after(0.2):
                 while True:
                     await send(
                         {
diff --git a/tests/test_templates.py b/tests/test_templates.py
@@ -23,7 +23,7 @@ def test_templates(tmpdir: Path, test_client_factory: TestClientFactory) -> None
     with open(path, "w") as file:
         file.write("<html>Hello, <a href='{{ url_for('homepage') }}'>world</a></html>")
 
-    async def homepage(request: Request) -> Response:
+    def homepage(request: Request) -> Response:
         return templates.TemplateResponse(request, "index.html")
 
     app = Starlette(debug=True, routes=[Route("/", endpoint=homepage)])
@@ -40,7 +40,7 @@ def test_calls_context_processors(tmp_path: Path, test_client_factory: TestClien
     path = tmp_path / "index.html"
     path.write_text("<html>Hello {{ username }}</html>")
 
-    async def homepage(request: Request) -> Response:
+    def homepage(request: Request) -> Response:
         return templates.TemplateResponse(request, "index.html")
 
     def hello_world_processor(request: Request) -> dict[str, str]:
@@ -69,7 +69,7 @@ def test_template_with_middleware(tmpdir: Path, test_client_factory: TestClientF
     with open(path, "w") as file:
         file.write("<html>Hello, <a href='{{ url_for('homepage') }}'>world</a></html>")
 
-    async def homepage(request: Request) -> Response:
+    def homepage(request: Request) -> Response:
         return templates.TemplateResponse(request, "index.html")
 
     class CustomMiddleware(BaseHTTPMiddleware):
@@ -96,15 +96,15 @@ def test_templates_with_directories(tmp_path: Path, test_client_factory: TestCli
     template_a = dir_a / "template_a.html"
     template_a.write_text("<html><a href='{{ url_for('page_a') }}'></a> a</html>")
 
-    async def page_a(request: Request) -> Response:
+    def page_a(request: Request) -> Response:
         return templates.TemplateResponse(request, "template_a.html")
 
     dir_b = tmp_path.resolve() / "b"
     dir_b.mkdir()
     template_b = dir_b / "template_b.html"
     template_b.write_text("<html><a href='{{ url_for('page_b') }}'></a> b</html>")
 
-    async def page_b(request: Request) -> Response:
+    def page_b(request: Request) -> Response:
         return templates.TemplateResponse(request, "template_b.html")
 
     app = Starlette(
@@ -150,7 +150,7 @@ def test_templates_with_environment(tmpdir: Path, test_client_factory: TestClien
     with open(path, "w") as file:
         file.write("<html>Hello, <a href='{{ url_for('homepage') }}'>world</a></html>")
 
-    async def homepage(request: Request) -> Response:
+    def homepage(request: Request) -> Response:
         return templates.TemplateResponse(request, "index.html")
 
     env = jinja2.Environment(loader=jinja2.FileSystemLoader(str(tmpdir)))

-Original file line number
+Diff line change
 .python-version
 build/
 dist/
 +.idea/