Code review fixes for #1444

yesod-core/Yesod/Core/Handler.hs

@@ -877,10 +877,14 @@ setEtag :: MonadHandler m => Text -> m ()
 setEtag etag = do
     mmatch <- lookupHeader "if-none-match"
     let matches = maybe [] parseMatch mmatch
-    if StrongEtag (encodeUtf8 etag) `elem` matches
+        baseTag = encodeUtf8 etag
+        strongTag = StrongEtag baseTag
+        badTag = InvalidEtag baseTag
+    if any (\tag -> tag == strongTag || tag == badTag) matches
         then notModified
         else addHeader "etag" $ T.concat ["\"", etag, "\""]
 
+
 -- | Parse an if-none-match field according to the spec.
 parseMatch :: S.ByteString -> [Etag]
 parseMatch =

yesod-core/test/YesodCoreTest/Redirect.hs

@@ -79,12 +79,14 @@ specs = describe "Redirect" $ do
         res <- request defaultRequest { pathInfo = ["etag"] }
         assertStatus 200 res
         assertHeader "etag" "\"hello world\"" res
+      -- Note: this violates the RFC around ETag format, but is being left as is
+      -- out of concerns that it might break existing users with misbehaving clients.
       it "single, unquoted if-none-match" $ app $ do
         res <- request defaultRequest
             { pathInfo = ["etag"]
             , requestHeaders = [("if-none-match", "hello world")]
             }
-        assertStatus 200 res
+        assertStatus 304 res
       it "different if-none-match" $ app $ do
         res <- request defaultRequest
             { pathInfo = ["etag"]