Add directory publish customisation point

This will help certain environments, such as P2P, where directory publishing can
be allowed freely.

src/components/views/room_settings/RoomPublishSetting.tsx

@@ -20,6 +20,7 @@ import LabelledToggleSwitch from "../elements/LabelledToggleSwitch";
 import { _t } from "../../../languageHandler";
 import { MatrixClientPeg } from "../../../MatrixClientPeg";
 import { replaceableComponent } from "../../../utils/replaceableComponent";
+import DirectoryCustomisations from '../../../customisations/Directory';
 
 interface IProps {
     roomId: string;
@@ -66,10 +67,15 @@ export default class RoomPublishSetting extends React.PureComponent<IProps, ISta
     render() {
         const client = MatrixClientPeg.get();
 
+        const enabled = (
+            DirectoryCustomisations.requireCanonicalAliasAccessToPublish?.() === false ||
+            this.props.canSetCanonicalAlias
+        );
+
         return (
             <LabelledToggleSwitch value={this.state.isRoomPublished}
                 onChange={this.onRoomPublishChange}
-                disabled={!this.props.canSetCanonicalAlias}
+                disabled={!enabled}
                 label={_t("Publish this room to the public in %(domain)s's room directory?", {
                     domain: client.getDomain(),
                 })}

src/customisations/Directory.ts

@@ -0,0 +1,31 @@
+/*
+Copyright 2021 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+function requireCanonicalAliasAccessToPublish(): boolean {
+    // Some environments may not care about this requirement and could return false
+    return true;
+}
+
+// This interface summarises all available customisation points and also marks
+// them all as optional. This allows customisers to only define and export the
+// customisations they need while still maintaining type safety.
+export interface IDirectoryCustomisations {
+    requireCanonicalAliasAccessToPublish?: typeof requireCanonicalAliasAccessToPublish;
+}
+
+// A real customisation module will define and export one or more of the
+// customisation points that make up `IDirectoryCustomisations`.
+export default {} as IDirectoryCustomisations;