compose_banner: Remove uploads banners when clearing compose box.

Upload banners were not cleared after closing compose box, which meant
that they would remain present in a paused state after compose was reopened.

https://chat.zulip.org/#narrow/stream/9-issues/topic/Incomplete.20Upload.20banner.20remains.20on.20closing.20compose/near/1582602

web/src/compose.js

@@ -187,6 +187,7 @@ export function clear_compose_box() {
     compose_ui.autosize_textarea($("#compose-textarea"));
     compose_banner.clear_errors();
     compose_banner.clear_warnings();
+    compose_banner.clear_uploads();
     compose_ui.hide_compose_spinner();
     popover_menus.reset_selected_schedule_timestamp();
 }

web/src/compose_actions.js

@@ -92,6 +92,7 @@ function clear_box() {
     compose_ui.autosize_textarea($("#compose-textarea"));
     compose_banner.clear_errors();
     compose_banner.clear_warnings();
+    compose_banner.clear_uploads();
 }
 
 export function autosize_message_content() {

web/src/compose_banner.ts

@@ -106,6 +106,10 @@ export function clear_warnings(): void {
     $(`#compose_banners .${CSS.escape(WARNING)}`).remove();
 }
 
+export function clear_uploads(): void {
+    $("#compose_banners .upload_banner").remove();
+}
+
 export function clear_unmute_topic_notifications(): void {
     $(`#compose_banners .${CLASSNAMES.unmute_topic_notification.replaceAll(" ", ".")}`).remove();
 }

web/src/compose_recipient.js

@@ -199,6 +199,7 @@ export function update_compose_for_message_type(message_type, opts) {
     }
     compose_banner.clear_errors();
     compose_banner.clear_warnings();
+    compose_banner.clear_uploads();
 }
 
 export function on_compose_select_recipient_update() {

web/tests/lib/compose_banner.js

@@ -12,6 +12,7 @@ exports.mock_banners = () => {
     }
     $("#compose_banners .warning").remove = () => {};
     $("#compose_banners .error").remove = () => {};
+    $("#compose_banners .upload_banner").remove = () => {};
 
     const $stub = $.create("stub_to_remove");
     const $cb = $("#compose_banners");