ComposeBox: Require topics if topics are set as mandatory.

(For stream messages, that is, not PMs.)

Fixes: #4378

Author: chrisbobbe

src/compose/ComposeBox.js

@@ -30,7 +30,7 @@ import { connect } from '../react-redux';
 import { withGetText } from '../boot/TranslationProvider';
 import { draftUpdate, sendTypingStart, sendTypingStop } from '../actions';
 import { FloatingActionButton, Input } from '../common';
-import { showToast } from '../utils/info';
+import { showToast, showErrorAlert } from '../utils/info';
 import { IconDone, IconSend } from '../common/Icons';
 import {
   isConversationNarrow,
@@ -46,7 +46,13 @@ import getComposeInputPlaceholder from './getComposeInputPlaceholder';
 import NotSubscribed from '../message/NotSubscribed';
 import AnnouncementOnly from '../message/AnnouncementOnly';
 import MentionWarnings from './MentionWarnings';
-import { getAuth, getIsAdmin, getStreamInNarrow, getVideoChatProvider } from '../selectors';
+import {
+  getAuth,
+  getIsAdmin,
+  getStreamInNarrow,
+  getVideoChatProvider,
+  getRealm,
+} from '../selectors';
 import {
   getIsActiveStreamSubscribed,
   getIsActiveStreamAnnouncementOnly,
@@ -64,6 +70,7 @@ type SelectorProps = {|
   isAnnouncementOnly: boolean,
   isSubscribed: boolean,
   videoChatProvider: VideoChatProvider | null,
+  mandatoryTopics: boolean,
   stream: Subscription | {| ...Stream, in_home_view: boolean |},
 |};
 
@@ -401,10 +408,21 @@ class ComposeBoxInner extends PureComponent<Props, State> {
   };
 
   handleSend = () => {
-    const { dispatch } = this.props;
+    const { dispatch, mandatoryTopics, _ } = this.props;
     const { message } = this.state;
     const destinationNarrow = this.getDestinationNarrow();
 
+    if (
+      isTopicNarrow(destinationNarrow)
+      && topicOfNarrow(destinationNarrow) === apiConstants.NO_TOPIC_TOPIC
+      && mandatoryTopics
+    ) {
+      // TODO how should this behave in the isEditing case? See
+      //   https://github.com/zulip/zulip-mobile/pull/4798#discussion_r731341400.
+      showErrorAlert(_('Message not sent'), _('Please specify a topic.'));
+      return;
+    }
+
     this.props.onSend(message, destinationNarrow);
 
     this.setMessageInputValue('');
@@ -588,6 +606,7 @@ const ComposeBox: ComponentType<OuterProps> = compose(
     isSubscribed: getIsActiveStreamSubscribed(state, props.narrow),
     stream: getStreamInNarrow(state, props.narrow),
     videoChatProvider: getVideoChatProvider(state),
+    mandatoryTopics: getRealm(state).mandatoryTopics,
   })),
   withSafeAreaInsets,
 )(withGetText(ComposeBoxInner));

static/translations/messages_en.json

@@ -1,4 +1,6 @@
 {
+  "Message not sent": "Message not sent",
+  "Please specify a topic.": "Please specify a topic.",
   "Failed to connect to server: {realm}": "Failed to connect to server: {realm}",
   "{_}": "{_}",
   "Home": "Home",