feat: introduce contentIsEmpty flag for messageComposer (#1705)

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- [ ] Code changes are tested

## Description of the changes, What, Why and How?


https://linear.app/stream/issue/REACT-891/user-should-be-able-to-quote-a-message-with-a-voice-message

- `compositionIsEmpty` -> used to track if draft can be discarded
- `contentIsEmpty` -> used to track if message has any content

## Changelog

-

Author: szuperaz

src/messageComposer/messageComposer.ts

@@ -344,8 +344,11 @@ export class MessageComposer extends WithSubscriptions {
   }
 
   get compositionIsEmpty() {
+    return !this.quotedMessage && this.contentIsEmpty;
+  }
+
+  get contentIsEmpty() {
     return (
-      !this.quotedMessage &&
       this.textComposer.textIsEmpty &&
       !this.attachmentManager.attachments.length &&
       !this.pollId &&

test/unit/MessageComposer/messageComposer.test.ts

@@ -624,6 +624,67 @@ describe('MessageComposer', () => {
 
       expect(messageComposer.compositionIsEmpty).toBe(true);
     });
+
+    describe('contentIsEmpty', () => {
+      it('is true when text, attachments, poll, and location are empty', () => {
+        const { messageComposer } = setup();
+        messageComposer.textComposer.state.partialNext({
+          text: '',
+          mentionedUsers: [],
+          selection: { start: 0, end: 0 },
+        });
+        expect(messageComposer.contentIsEmpty).toBe(true);
+      });
+
+      it('is false when text, attachments, poll, or valid location is set', () => {
+        const { messageComposer } = setup();
+        messageComposer.textComposer.state.partialNext({
+          text: '',
+          mentionedUsers: [],
+          selection: { start: 0, end: 0 },
+        });
+
+        messageComposer.textComposer.state.partialNext({ text: 'hi' });
+        expect(messageComposer.contentIsEmpty).toBe(false);
+        messageComposer.textComposer.state.partialNext({ text: '' });
+
+        messageComposer.attachmentManager.state.partialNext({
+          attachments: [
+            { type: 'x', localMetadata: { id: 'x', uploadState: 'finished', file: {} } },
+          ],
+        });
+        expect(messageComposer.contentIsEmpty).toBe(false);
+        messageComposer.attachmentManager.state.partialNext({ attachments: [] });
+
+        messageComposer.state.partialNext({ pollId: 'poll-id' });
+        expect(messageComposer.contentIsEmpty).toBe(false);
+        messageComposer.state.partialNext({ pollId: null });
+
+        messageComposer.updateConfig({ location: { enabled: true } });
+        messageComposer.locationComposer.setData({ latitude: 1, longitude: 1 });
+        expect(messageComposer.contentIsEmpty).toBe(false);
+      });
+
+      it('is unaffected by quoted message (unlike compositionIsEmpty)', () => {
+        const { messageComposer } = setup();
+        messageComposer.textComposer.state.partialNext({
+          text: '',
+          mentionedUsers: [],
+          selection: { start: 0, end: 0 },
+        });
+        messageComposer.setQuotedMessage({
+          id: 'id',
+          type: 'regular',
+          status: 'delivered',
+          created_at: new Date(),
+          updated_at: new Date(),
+          deleted_at: null,
+          pinned_at: null,
+        });
+        expect(messageComposer.contentIsEmpty).toBe(true);
+        expect(messageComposer.compositionIsEmpty).toBe(false);
+      });
+    });
   });
 
   describe('offlineDB enabled', () => {