Implement MSC 4228 Search Redirection

See https://github.com/matrix-org/matrix-spec-proposals/pull/4228 for details.
Since this is tricky to test without server-side support, I have added a basic implementation
to the mock server in appiumtests/login-server.py

1. Start appiumtests/login-server.py
2. Start neochat with "--test --ignore-ssl-errors" options
3. Open "Explore Rooms"
4. Search for the exact string "forbidden"
5. See new error message provided by server

appiumtests/login-server.py

@@ -83,6 +83,15 @@ def create_room():
     next_sync_payload = "sync_response_new_room"
     return response
 
+@app.route("/_matrix/client/v3/publicRooms", methods=["POST"])
+def public_rooms():
+    if request.get_json()["filter"]["generic_search_term"] == "forbidden":
+        data = dict()
+        data["errcode"] = "M_FORBIDDEN"
+        data["error"] = "You are not allowed to search for this. Go to https://wikipedia.org for more information"
+        return data, 403
+    return dict()
+
 
 
 if __name__ == "__main__":

src/models/publicroomlistmodel.cpp

@@ -8,6 +8,23 @@
 
 using namespace Quotient;
 
+class NeoChatQueryPublicRoomsJob : public QueryPublicRoomsJob
+{
+public:
+    explicit NeoChatQueryPublicRoomsJob(const QString &server = {},
+                                        std::optional<int> limit = std::nullopt,
+                                        const QString &since = {},
+                                        const std::optional<Filter> &filter = std::nullopt,
+                                        std::optional<bool> includeAllNetworks = std::nullopt,
+                                        const QString &thirdPartyInstanceId = {})
+        : QueryPublicRoomsJob(server, limit, since, filter, includeAllNetworks, thirdPartyInstanceId)
+    {
+        // TODO Remove once we can use libQuotient's job directly
+        // This is to make libQuotient happy about results not having the "chunk" field
+        setExpectedKeys({});
+    }
+};
+
 PublicRoomListModel::PublicRoomListModel(QObject *parent)
     : QAbstractListModel(parent)
 {
@@ -153,6 +170,8 @@ void PublicRoomListModel::next(int limit)
     if (m_connection == nullptr || limit < 1) {
         return;
     }
+    m_redirectedText.clear();
+    Q_EMIT redirectedChanged();
 
     if (job) {
         qCDebug(PublicRoomList) << "Other job running, ignore";
@@ -163,7 +182,7 @@ void PublicRoomListModel::next(int limit)
     if (m_showOnlySpaces) {
         roomTypes += QLatin1String("m.space");
     }
-    job = m_connection->callApi<QueryPublicRoomsJob>(m_server, limit, nextBatch, QueryPublicRoomsJob::Filter{m_searchText, roomTypes});
+    job = m_connection->callApi<NeoChatQueryPublicRoomsJob>(m_server, limit, nextBatch, QueryPublicRoomsJob::Filter{m_searchText, roomTypes});
     Q_EMIT searchingChanged();
 
     connect(job, &BaseJob::finished, this, [this] {
@@ -181,6 +200,9 @@ void PublicRoomListModel::next(int limit)
             this->beginInsertRows({}, rooms.count(), rooms.count() + job->chunk().count() - 1);
             rooms.append(job->chunk());
             this->endInsertRows();
+        } else if (job->error() == BaseJob::ContentAccessError) {
+            m_redirectedText = job->jsonData()[u"error"_s].toString();
+            Q_EMIT redirectedChanged();
         }
 
         this->job = nullptr;
@@ -302,4 +324,9 @@ bool PublicRoomListModel::searching() const
     return job != nullptr;
 }
 
+QString PublicRoomListModel::redirectedText() const
+{
+    return m_redirectedText;
+}
+
 #include "moc_publicroomlistmodel.cpp"

src/models/publicroomlistmodel.h

@@ -52,6 +52,11 @@ class PublicRoomListModel : public QAbstractListModel
      */
     Q_PROPERTY(bool searching READ searching NOTIFY searchingChanged)
 
+    /**
+     * @brief The text returned by the server after redirection
+     */
+    Q_PROPERTY(QString redirectedText READ redirectedText NOTIFY redirectedChanged)
+
 public:
     /**
      * @brief Defines the model roles.
@@ -113,6 +118,8 @@ public:
      */
     Q_INVOKABLE void search(int limit = 50);
 
+    QString redirectedText() const;
+
 private:
     QPointer<NeoChatConnection> m_connection = nullptr;
     QString m_server;
@@ -135,6 +142,7 @@ private:
     QList<Quotient::PublicRoomsChunk> rooms;
 
     Quotient::QueryPublicRoomsJob *job = nullptr;
+    QString m_redirectedText;
 
 Q_SIGNALS:
     void connectionChanged();
@@ -142,4 +150,5 @@ Q_SIGNALS:
     void searchTextChanged();
     void showOnlySpacesChanged();
     void searchingChanged();
+    void redirectedChanged();
 };

src/qml/ExploreRoomsPage.qml

@@ -50,6 +50,8 @@ SearchPage {
     signal roomSelected(string roomId, string displayName, url avatarUrl, string alias, string topic, int memberCount, bool isJoined)
 
     title: i18nc("@action:title", "Explore Rooms")
+    customPlaceholderText: publicRoomListModel.redirectedText
+    customPlaceholderIcon: "data-warning"
 
     Component.onCompleted: focusSearch()
 
@@ -93,6 +95,7 @@ SearchPage {
 
         activeFocusOnTab: false // We handle moving to this item via up/down arrows, otherwise the tab order is wacky
         text: i18n("Enter a Room Manually")
+        visible: publicRoomListModel.redirectedText.length === 0
         icon.name: "compass"
         icon.width: Kirigami.Units.gridUnit * 2
         icon.height: Kirigami.Units.gridUnit * 2

src/qml/SearchPage.qml

@@ -80,6 +80,17 @@ Kirigami.ScrollablePage {
      */
     property bool showSearchButton: true
 
+    /**
+     * @brief Message to be shown in a custom placeholder.
+     * The custom placeholder will be shown if the text is not empty
+     */
+    property alias customPlaceholderText: customPlaceholder.text
+
+    /**
+     * @brief icon for the custom placeholder
+     */
+    property string customPlaceholderIcon: ""
+
     /**
      * @brief Force the search field to be focussed.
      */
@@ -167,18 +178,25 @@ Kirigami.ScrollablePage {
         Kirigami.PlaceholderMessage {
             id: noSearchMessage
             anchors.centerIn: parent
-            visible: searchField.text.length === 0 && listView.count === 0
+            visible: searchField.text.length === 0 && listView.count === 0 && !root.showCustomPlaceholder && customPlaceholder.text.length === 0
         }
 
         Kirigami.PlaceholderMessage {
             id: noResultMessage
             anchors.centerIn: parent
-            visible: searchField.text.length > 0 && listView.count === 0 && !root.model.searching
+            visible: searchField.text.length > 0 && listView.count === 0 && !root.model.searching && customPlaceholder.text.length === 0
+        }
+
+        Kirigami.PlaceholderMessage {
+            id: customPlaceholder
+            anchors.centerIn: parent
+            visible: searchField.text.length > 0 && listView.count === 0 && !root.model.searching && text.length > 0
+            icon.name: root.customPlaceholderIcon
         }
 
         Kirigami.LoadingPlaceholder {
             anchors.centerIn: parent
-            visible: searchField.text.length > 0 && listView.count === 0 && root.model.searching
+            visible: searchField.text.length > 0 && listView.count === 0 && root.model.searching && customPlaceholder.text.length === 0
         }
 
         Keys.onUpPressed: {