[IMP] mail: turn 'Discuss/addChannelInputPlaceholder' into field

Task-2793280

closes odoo/odoo#86442

Signed-off-by: Ooming <wil@odoo.com>

addons/mail/static/src/components/discuss/discuss.js

@@ -41,13 +41,6 @@ export class Discuss extends LegacyComponent {
     // Public
     //--------------------------------------------------------------------------
 
-    /**
-     * @returns {string}
-     */
-    get addChannelInputPlaceholder() {
-        return this.env._t("Create or search channel...");
-    }
-
     /**
      * @returns {string}
      */

addons/mail/static/src/components/discuss/discuss.xml

@@ -33,7 +33,7 @@
                     className="'o_Discuss_mobileAddItemHeaderInput'"
                     isFocusOnMount="true"
                     isHtml="discussView.discuss.isAddingChannel"
-                    placeholder="discussView.discuss.isAddingChannel ? addChannelInputPlaceholder : addChatInputPlaceholder"
+                    placeholder="discussView.discuss.isAddingChannel ? discuss.addChannelInputPlaceholder : addChatInputPlaceholder"
                     select="_onMobileAddItemHeaderInputSelect"
                     source="_onMobileAddItemHeaderInputSource"
                     onHide="_onHideMobileAddItemHeader"

addons/mail/static/src/models/discuss/discuss.js

@@ -232,6 +232,13 @@ registerModel({
             }
             return this.threadToActiveId(this.thread);
         },
+        /**
+         * @private
+         * @returns {string}
+         */
+        _computeAddChannelInputPlaceholder() {
+            return this.env._t("Create or search channel...");
+        },
         /**
          * @private
          * @returns {string}
@@ -336,6 +343,9 @@ registerModel({
         activeMobileNavbarTabId: attr({
             default: 'mailbox',
         }),
+        addChannelInputPlaceholder: attr({
+            compute: '_computeAddChannelInputPlaceholder',
+        }),
         /**
          * Value that is used to create a channel from the sidebar.
          */