allow empty message when they have attachments

_locales/en/messages.json

@@ -1275,7 +1275,11 @@
   },
   "messageBodyTooLong": {
     "message": "Message body is too long.",
-    "description": "Shown if the user tries to send more than 64kb of text"
+    "description": "Shown if the user tries to send more than MAX_MESSAGE_BODY_LENGTH chars"
+  },
+  "messageBodyMissing": {
+    "message": "Please enter a message body.",
+    "description": "Shown if the user tries to send an empty message (and no attachments)"
   },
   "unblockToSend": {
     "message": "Unblock this contact to send a message.",

ts/components/session/conversation/SessionCompositionBox.tsx

@@ -325,13 +325,14 @@ export class SessionCompositionBox extends React.Component<Props, State> {
   private async onSendMessage() {
     const messagePlaintext = this.parseEmojis(this.state.message);
 
-    if (!messagePlaintext) {
+    // Verify message length
+    const msgLen = messagePlaintext?.length || 0;
+    if (msgLen > window.CONSTANTS.MAX_MESSAGE_BODY_LENGTH) {
+      ToastUtils.pushMessageBodyTooLong();
       return;
     }
-
-    // Verify message length
-    const msgLen = messagePlaintext.length;
-    if (msgLen === 0 || msgLen > window.CONSTANTS.MAX_MESSAGE_BODY_LENGTH) {
+    if (msgLen === 0 && this.state.stagedAttachments?.length === 0) {
+      ToastUtils.pushMessageBodyMissing();
       return;
     }
     const { quotedMessageProps } = this.props;

ts/session/utils/Toast.ts

@@ -57,3 +57,19 @@ export function pushMaximumAttachmentsError() {
     id: 'maximumAttachments',
   });
 }
+
+export function pushMessageBodyTooLong() {
+  window.pushToast({
+    title: window.i18n('messageBodyTooLong'),
+    type: 'error',
+    id: 'messageBodyTooLong',
+  });
+}
+
+export function pushMessageBodyMissing() {
+  window.pushToast({
+    title: window.i18n('messageBodyMissing'),
+    type: 'error',
+    id: 'messageBodyMissing',
+  });
+}