Add if_match and if_none_match properties

aiohttp/web_request.py

@@ -32,7 +32,10 @@
 from .abc import AbstractStreamWriter
 from .helpers import (
     _SENTINEL,
+    ETAG_ANY,
+    LIST_QUOTED_ETAG_RE,
     ChainMapProxy,
+    ETag,
     HeadersMixin,
     is_expected_content_type,
     reify,
@@ -494,6 +497,47 @@ def if_unmodified_since(self) -> Optional[datetime.datetime]:
         """
         return self._http_date(self.headers.get(hdrs.IF_UNMODIFIED_SINCE))
 
+    @staticmethod
+    def _etag_values(etag_header: str) -> Iterator[ETag]:
+        """Extract `ETag` objects from raw header."""
+        if etag_header == ETAG_ANY:
+            yield ETag(
+                is_weak=False,
+                value=ETAG_ANY,
+            )
+        else:
+            for match in LIST_QUOTED_ETAG_RE.finditer(etag_header):
+                is_weak, quoted_value = match.group(2), match.group(3)
+                yield ETag(
+                    is_weak=bool(is_weak),
+                    value=quoted_value[1:-1],
+                )
+
+    @classmethod
+    def _if_match_or_none_impl(
+        cls, header_value: Optional[str]
+    ) -> Optional[Tuple[ETag, ...]]:
+        if not header_value:
+            return None
+
+        return tuple(cls._etag_values(header_value))
+
+    @reify
+    def if_match(self) -> Optional[Tuple[ETag, ...]]:
+        """The value of If-Match HTTP header, or None.
+
+        This header is represented as a `tuple` of `ETag` objects.
+        """
+        return self._if_match_or_none_impl(self.headers.get(hdrs.IF_MATCH))
+
+    @reify
+    def if_none_match(self) -> Optional[Tuple[ETag, ...]]:
+        """The value of If-None-Match HTTP header, or None.
+
+        This header is represented as a `tuple` of `ETag` objects.
+        """
+        return self._if_match_or_none_impl(self.headers.get(hdrs.IF_NONE_MATCH))
+
     @reify
     def if_range(self) -> Optional[datetime.datetime]:
         """The value of If-Range HTTP header, or None.

docs/web_reference.rst

@@ -318,6 +318,24 @@ and :ref:`aiohttp-web-signals` handlers.
 
       .. versionadded:: 3.1
 
+   .. attribute:: if_match
+
+      Read-only property that returns :class:`ETag` objects specified
+      in the *If-Match* header.
+
+      Returns :class:`tuple` of :class:`ETag` or ``None`` if
+      *If-Match* header is absent.
+
+   .. attribute:: if_none_match
+
+      Read-only property that returns :class:`ETag` objects specified
+      *If-None-Match* header.
+
+      Returns :class:`tuple` of :class:`ETag` or ``None`` if
+      *If-None-Match* header is absent.
+
+      .. versionadded:: 4.0
+
    .. attribute:: if_range
 
       Read-only property that returns the date specified in the

tests/test_web_request.py

@@ -17,6 +17,7 @@
 from aiohttp.streams import StreamReader
 from aiohttp.test_utils import make_mocked_request
 from aiohttp.web import HTTPRequestEntityTooLarge, HTTPUnsupportedMediaType
+from aiohttp.web_request import ETag
 
 
 @pytest.fixture
@@ -820,3 +821,36 @@ async def invalid_handler_1(request):
 
     async with client.get("/1") as resp:
         assert 500 == resp.status
+
+
+@pytest.mark.parametrize(
+    "header,header_attr",
+    [
+        pytest.param("If-Match", "if_match"),
+        pytest.param("If-None-Match", "if_none_match"),
+    ],
+)
+@pytest.mark.parametrize(
+    "header_val,expected",
+    [
+        pytest.param(
+            '"67ab43", W/"54ed21", "7892dd"',
+            (
+                ETag(is_weak=False, value="67ab43"),
+                ETag(is_weak=True, value="54ed21"),
+                ETag(is_weak=False, value="7892dd"),
+            ),
+        ),
+        pytest.param(
+            '"bfc1ef-5b2c2730249c88ca92d82d"',
+            (ETag(is_weak=False, value="bfc1ef-5b2c2730249c88ca92d82d"),),
+        ),
+        pytest.param(
+            "*",
+            (ETag(is_weak=False, value="*"),),
+        ),
+    ],
+)
+def test_etag_headers(header, header_attr, header_val, expected) -> None:
+    req = make_mocked_request("GET", "/", headers={header: header_val})
+    assert getattr(req, header_attr) == expected