Only show jump to date feature flag when your homserver supports it

See #7372 (comment)

Author: MadLittleMods

src/components/views/settings/tabs/user/LabsUserSettingsTab.tsx

@@ -49,6 +49,7 @@ export class LabsSettingToggle extends React.Component<ILabsSettingToggleProps>
 
 interface IState {
     showHiddenReadReceipts: boolean;
+    showJumpToDate: boolean;
 }
 
 @replaceableComponent("views.settings.tabs.user.LabsUserSettingsTab")
@@ -60,8 +61,13 @@ export default class LabsUserSettingsTab extends React.Component<{}, IState> {
             this.setState({ showHiddenReadReceipts });
         });
 
+        MatrixClientPeg.get().doesServerSupportUnstableFeature("org.matrix.msc2716").then((showJumpToDate) => {
+            this.setState({ showJumpToDate });
+        });
+
         this.state = {
             showHiddenReadReceipts: false,
+            showJumpToDate: false,
         };
     }
 
@@ -135,6 +141,16 @@ export default class LabsUserSettingsTab extends React.Component<{}, IState> {
                 );
             }
 
+            if (this.state.showJumpToDate) {
+                groups.getOrCreate(LabGroup.Messaging, []).push(
+                    <SettingsFlag
+                        key="feature_jump_to_date"
+                        name="feature_jump_to_date"
+                        level={SettingLevel.DEVICE}
+                    />,
+                );
+            }
+
             labsSection = <div className="mx_SettingsTab_section">
                 { sortBy(Array.from(groups.entries()), "0").map(([group, flags]) => (
                     <div key={group}>

src/settings/Settings.tsx

@@ -368,9 +368,11 @@ export const SETTINGS: {[setting: string]: ISetting} = {
         default: false,
     },
     "feature_jump_to_date": {
-        isFeature: true,
-        labsGroup: LabGroup.Messaging,
-        displayName: _td("Jump to date (adds /jumptodate). Also requires your homeserver to have MSC3030 enabled"),
+        // We purposely leave out `isFeature: true` so it doesn't show in Labs
+        // by default. We will conditionally show it depending on whether we can
+        // detect MSC3030 support (see LabUserSettingsTab.tsx).
+        // labsGroup: LabGroup.Messaging,
+        displayName: _td("Jump to date (adds /jumptodate)"),
         supportedLevels: LEVELS_FEATURE,
         default: false,
     },