HTTP caching internals: fix logic for PreferNetwork and PreferCache

PreferNetwork means: send out a request and read from cache if it has
                     not been modified.
PreferCache means: load resource from cache if it has not expired yet.

This commit makes the cache behave according to the documentation.

Reviewed-by: Markus Goetz

1 files changed, 6 insertions, 1 deletions

diff --git a/src/network/access/qnetworkaccesshttpbackend.cpp b/src/network/access/qnetworkaccesshttpbackend.cpp
index 0438fb5..4ac0a67 100644
--- a/src/network/access/qnetworkaccesshttpbackend.cpp
+++ b/src/network/access/qnetworkaccesshttpbackend.cpp
@@ -262,6 +262,11 @@ bool QNetworkAccessHttpBackend::loadFromCacheIfAllowed(QHttpNetworkRequest &http
         httpRequest.setHeaderField("If-Modified-Since", QNetworkHeadersPrivate::toHttpDate(lastModified));
 
     if (CacheLoadControlAttribute == QNetworkRequest::PreferNetwork) {
+        // PreferNetwork == send request with "If-None-Match" and "If-Modified-Since" header,
+        // which will return a 304 Not Modifed if resource has not been changed.
+        // We might read from cache later, if receiving a 304.
+        return false;
+    } else if (CacheLoadControlAttribute == QNetworkRequest::PreferCache) {
         it = cacheHeaders.findRawHeader("Cache-Control");
         if (it != cacheHeaders.rawHeaders.constEnd()) {
             QHash<QByteArray, QByteArray> cacheControl = parseHttpOptionHeader(it->second);
@@ -1145,7 +1150,7 @@ QNetworkCacheMetaData QNetworkAccessHttpBackend::fetchCacheMetaData(const QNetwo
         attributes.insert(QNetworkRequest::HttpStatusCodeAttribute, statusCode);
         attributes.insert(QNetworkRequest::HttpReasonPhraseAttribute, reasonPhrase);
     } else {
-        // this is a redirection, keep the attributes intact
+        // this is the server telling us the resource has not changed, keep the attributes intact
         attributes = oldMetaData.attributes();
     }
     metaData.setAttributes(attributes);