compose: Add button to save draft and start a new message.

web/src/compose_actions.ts

@@ -305,6 +305,7 @@ export function start(raw_opts: ComposeActionsStartOpts): void {
     // If we're not explicitly opening a different draft, restore the last
     // saved draft (if it exists).
     if (
+        compose_state.can_restore_drafts() &&
         !opts.content &&
         opts.draft_id === undefined &&
         compose_state.message_content().length === 0

web/src/compose_state.ts

@@ -190,6 +190,11 @@ export function has_message_content(): boolean {
     return message_content() !== "";
 }
 
+export const MINIMUM_MESSAGE_LENGTH_TO_SAVE_DRAFT = 2;
+export function has_savable_message_content(): boolean {
+    return message_content().length > MINIMUM_MESSAGE_LENGTH_TO_SAVE_DRAFT;
+}
+
 export function has_full_recipient(): boolean {
     if (message_type === "stream") {
         return stream_id() !== undefined && topic() !== "";
@@ -208,3 +213,16 @@ export function update_email(user_id: number, new_email: string): void {
 
     private_message_recipient(reply_to);
 }
+
+let _can_restore_drafts = true;
+export function prevent_draft_restoring(): void {
+    _can_restore_drafts = false;
+}
+
+export function allow_draft_restoring(): void {
+    _can_restore_drafts = true;
+}
+
+export function can_restore_drafts(): boolean {
+    return _can_restore_drafts;
+}

web/src/drafts.ts

@@ -281,7 +281,10 @@ export function rename_stream_recipient(
 }
 
 export function snapshot_message(): LocalStorageDraft | undefined {
-    if (!compose_state.composing() || compose_state.message_content().length <= 2) {
+    if (
+        !compose_state.composing() ||
+        compose_state.message_content().length <= compose_state.MINIMUM_MESSAGE_LENGTH_TO_SAVE_DRAFT
+    ) {
         // If you aren't in the middle of composing the body of a
         // message or the message is shorter than 2 characters long, don't try to snapshot.
         return undefined;

web/src/narrow.js

@@ -68,6 +68,8 @@ export function reset_ui_state() {
     message_feed_top_notices.hide_top_of_narrow_notices();
     message_feed_loading.hide_indicators();
     unread_ui.reset_unread_banner();
+    // We sometimes prevent draft restoring until the narrow resets.
+    compose_state.allow_draft_restoring();
 }
 
 export function changehash(newhash) {

web/src/scheduled_messages_popover.js

@@ -9,6 +9,7 @@ import * as blueslip from "./blueslip";
 import * as channel from "./channel";
 import * as common from "./common";
 import * as compose from "./compose";
+import * as compose_state from "./compose_state";
 import * as compose_validate from "./compose_validate";
 import * as drafts from "./drafts";
 import * as flatpickr from "./flatpickr";
@@ -151,11 +152,15 @@ export function initialize() {
         onShow(instance) {
             const formatted_send_later_time =
                 scheduled_messages.get_formatted_selected_send_later_time();
+            // If there's existing text in the composebox, show an option
+            // to keep/save the current draft and start a new message.
+            const show_compose_new_message = compose_state.has_savable_message_content();
             instance.setContent(
                 parse_html(
                     render_send_later_popover({
                         enter_sends_true: user_settings.enter_sends,
                         formatted_send_later_time,
+                        show_compose_new_message,
                     }),
                 ),
             );
@@ -203,6 +208,19 @@ export function initialize() {
                 open_send_later_menu();
                 popover_menus.hide_current_popover_if_visible(instance);
             });
+            $popper.one("click", ".compose_new_message", () => {
+                drafts.update_draft();
+                // If they want to compose a new message instead
+                // of seeing the draft, remember this and don't
+                // restore drafts in this narrow until the user
+                // switches narrows. This allows a user to send
+                // a bunch of messages in a conversation without
+                // clicking the "start a new draft" button every
+                // time.
+                compose_state.prevent_draft_restoring();
+                compose.clear_compose_box();
+                popover_menus.hide_current_popover_if_visible(instance);
+            });
         },
         onHidden(instance) {
             instance.destroy();

web/templates/popovers/send_later_popover.hbs

@@ -53,4 +53,10 @@
     <li class="drafts-item-in-popover">
         <a href="#drafts">{{t "Drafts" }} <span class="compose-drafts-count-container">(<span class="compose-drafts-count"></span>)</span></a>
     </li>
+    {{#if show_compose_new_message}}
+    <hr />
+    <li>
+        <a class="compose_new_message" tabindex=="0">{{t "Save draft and start a new message" }}</a>
+    </li>
+    {{/if}}
 </ul>