Support using system llhttp library

CHANGES/10759.packaging.rst

@@ -0,0 +1,5 @@
+Added support for building against system ``llhttp`` library -- by :user:`mgorny`.
+
+This change adds support for :envvar:`AIOHTTP_USE_SYSTEM_DEPS` environment variable that
+can be used to build aiohttp against the system install of the ``llhttp`` library rather
+than the vendored one.

aiohttp/_cparser.pxd

@@ -1,7 +1,7 @@
 from libc.stdint cimport int32_t, uint8_t, uint16_t, uint64_t
 
 
-cdef extern from "../vendor/llhttp/build/llhttp.h":
+cdef extern from "llhttp.h":
 
     struct llhttp__internal_s:
         int32_t _index

docs/glossary.rst

@@ -151,6 +151,17 @@
 Environment Variables
 =====================
 
+.. envvar:: AIOHTTP_NO_EXTENSIONS
+
+   If set to a non-empty value while building from source, aiohttp will be built without speedups
+   written as C extensions. This option is primarily useful for debugging.
+
+.. envvar:: AIOHTTP_USE_SYSTEM_DEPS
+
+   If set to a non-empty value while building from source, aiohttp will be built against
+   the system installation of llhttp rather than the vendored library. This option is primarily
+   meant to be used by downstream redistributors.
+
 .. envvar:: NETRC
 
    If set, HTTP Basic Auth will be read from the file pointed to by this environment variable,

docs/spelling_wordlist.txt

@@ -176,6 +176,7 @@ kwargs
 latin
 lifecycle
 linux
+llhttp
 localhost
 Locator
 login

pyproject.toml

@@ -1,5 +1,6 @@
 [build-system]
 requires = [
+    "pkgconfig",
     "setuptools >= 46.4.0",
 ]
 build-backend = "setuptools.build_meta"

requirements/test.in

@@ -5,6 +5,7 @@ coverage
 freezegun
 isal
 mypy; implementation_name == "cpython"
+pkgconfig
 proxy.py >= 2.4.4rc5
 pytest
 pytest-cov

setup.py

@@ -8,6 +8,9 @@
     raise RuntimeError("aiohttp 4.x requires Python 3.9+")
 
 
+USE_SYSTEM_DEPS = bool(
+    os.environ.get("AIOHTTP_USE_SYSTEM_DEPS", os.environ.get("USE_SYSTEM_DEPS"))
+)
 NO_EXTENSIONS: bool = bool(os.environ.get("AIOHTTP_NO_EXTENSIONS"))
 HERE = pathlib.Path(__file__).parent
 IS_GIT_REPO = (HERE / ".git").exists()
@@ -17,7 +20,11 @@
     NO_EXTENSIONS = True
 
 
-if IS_GIT_REPO and not (HERE / "vendor/llhttp/README.md").exists():
+if (
+    not USE_SYSTEM_DEPS
+    and IS_GIT_REPO
+    and not (HERE / "vendor/llhttp/README.md").exists()
+):
     print("Install submodules when building from git clone", file=sys.stderr)
     print("Hint:", file=sys.stderr)
     print("  git submodule update --init", file=sys.stderr)
@@ -26,19 +33,37 @@
 
 # NOTE: makefile cythonizes all Cython modules
 
+if USE_SYSTEM_DEPS:
+    import shlex
+
+    import pkgconfig
+
+    llhttp_sources = []
+    llhttp_kwargs = {
+        "extra_compile_args": shlex.split(pkgconfig.cflags("libllhttp")),
+        "extra_link_args": shlex.split(pkgconfig.libs("libllhttp")),
+    }
+else:
+    llhttp_sources = [
+        "vendor/llhttp/build/c/llhttp.c",
+        "vendor/llhttp/src/native/api.c",
+        "vendor/llhttp/src/native/http.c",
+    ]
+    llhttp_kwargs = {
+        "define_macros": [("LLHTTP_STRICT_MODE", 0)],
+        "include_dirs": ["vendor/llhttp/build"],
+    }
+
 extensions = [
     Extension("aiohttp._websocket.mask", ["aiohttp/_websocket/mask.c"]),
     Extension(
         "aiohttp._http_parser",
         [
             "aiohttp/_http_parser.c",
             "aiohttp/_find_header.c",
-            "vendor/llhttp/build/c/llhttp.c",
-            "vendor/llhttp/src/native/api.c",
-            "vendor/llhttp/src/native/http.c",
+            *llhttp_sources,
         ],
-        define_macros=[("LLHTTP_STRICT_MODE", 0)],
-        include_dirs=["vendor/llhttp/build"],
+        **llhttp_kwargs,
     ),
     Extension("aiohttp._http_writer", ["aiohttp/_http_writer.c"]),
     Extension("aiohttp._websocket.reader_c", ["aiohttp/_websocket/reader_c.c"]),