[FIX] mail: no traceback on click channel mention from chat window

Before this commit, when clicking on a channel mention from a chat
window, it crashed with the following error:

`TypeError: channel.detach is not a function`

This happens due to `MailService.joinChannel()` returning a promise
that is resolved with channel ID, instead of a channel object.
`channel.detach()` becomes `<Number>.detach()`, which is treated
like `undefined()`, hence crash.

closes odoo/odoo#44329

X-original-commit: 710fda06
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/js/thread_windows/thread_window.js

@@ -351,10 +351,12 @@ var ThreadWindow = AbstractThreadWindow.extend({
      * @param {integer} channelID
      */
     _onRedirectToChannel: function (channelID) {
+        var self = this;
         var thread = this.call('mail_service', 'getThread', channelID);
         if (!thread) {
             this.call('mail_service', 'joinChannel', channelID)
-                .then(function (channel) {
+                .then(function (channelID) {
+                    var channel = self.call('mail_service', 'getThread', channelID);
                     channel.detach();
                 });
         } else {

addons/mail/static/tests/thread_window/basic_thread_window_tests.js

@@ -903,6 +903,92 @@ QUnit.test('non-deletable message attachments', async function (assert) {
     parent.destroy();
 });
 
+QUnit.test('join channel from click channel mention', async function (assert) {
+    assert.expect(10);
+
+    this.data['mail.channel'].records = [{
+        id: 2,
+        name: "R&D Tasks",
+        channel_type: "channel",
+    }];
+    this.data['mail.message'].records.push({
+        author_id: [5, "Someone else"],
+        body: `<p><a href="#" class="o_mail_redirect" data-oe-id="2" data-oe-model="mail.channel">#R&D Tasks</a></p>`,
+        id: 10,
+        res_id: 1,
+        channel_ids: [1],
+    });
+
+    const parent = this.createParent({
+        data: this.data,
+        services: this.services,
+        session: { partner_id: 3 },
+        async mockRPC(route, args) {
+            if (args.method === 'channel_join_and_get_info') {
+                const channelID = args.args[0][0];
+                assert.step(`channel_join_and_get_info:${channelID}`);
+                return this.data['mail.channel'].records.find(channel => channel.id === channelID);
+            }
+            return this._super(...arguments);
+        },
+    });
+    await testUtils.nextTick();
+    assert.containsNone(
+        $,
+        '.o_thread_window',
+        "no thread window should be open initially"
+    );
+
+    // get channel instance to link to thread window
+    const channel = parent.call('mail_service', 'getChannel', 1);
+    channel.detach();
+    await testUtils.nextTick();
+    assert.containsOnce(
+        $,
+        '.o_thread_window',
+        "should have one thread open in chat window"
+    );
+    assert.strictEqual(
+        $('.o_thread_window .o_thread_window_title').text().trim(),
+        "#general",
+        "should have thread '#general' as open in chat window"
+    );
+    assert.containsOnce(
+        $,
+        '.o_thread_window .o_thread_message',
+        "should contain a single message in chat window"
+    );
+    assert.containsOnce(
+        $,
+        '.o_thread_window .o_thread_message a.o_mail_redirect',
+        "message should have a mention"
+    );
+    assert.containsOnce(
+        $,
+        '.o_thread_window .o_thread_message a.o_mail_redirect[data-oe-id="2"][data-oe-model="mail.channel"]',
+        "message should have a channel mention to R&D Task"
+    );
+
+    await testUtils.dom.click($('.o_thread_window .o_thread_message a.o_mail_redirect[data-oe-id="2"][data-oe-model="mail.channel"]'));
+    assert.verifySteps(
+        ['channel_join_and_get_info:2'],
+        "should have joined channel #R&D Task"
+    );
+    assert.containsN(
+        $,
+        '.o_thread_window',
+        2,
+        "should now have 2 threads open in chat windows after cliking on channel mention"
+    );
+    assert.strictEqual(
+        $('.o_thread_window .o_thread_window_title').text().replace(/\s/g, ""),
+        "#general#R&DTasks",
+        "should have threads '#general' and '#R&D Tasks' as open in chat windows"
+    );
+
+    parent.destroy();
+});
+
 });
 });
 });