[REF] mail, *: refactor messaging with OWL

This commit is a significant rewriting of client-side discuss, chatter,
chat window, and messaging menu using OWL. The behavior should be broadly
the same, with some slight functional changes here and there.

From a technical standpoint, the code of messaging is mainly organized in 2
main groups of modules:

- models, which are logical entities that depict the client-side state of
  messaging as a whole.
- components, which are in charge of displaying information from models.

This refactoring also introduces new JS guidelines regarding folder structure
(/static) and naming rules for JS modules.

Community PR: https://github.com/odoo/odoo/pull/39023
Enterprise PR: https://github.com/odoo/enterprise/pull/6249

Task-1914207

This PR is a collaborative work by Alexandre, Julien, Sébastien and Xavier,
with the precious help of Lucas to speed it up towards the end.

closes odoo/odoo#39023

Related: odoo/enterprise#6249
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>
Co-authored-by: Alexandre Kühn <aku@odoo.com>
Co-authored-by: Julien Giannone <jgi@odoo.com>
Co-authored-by: Lucas Perais <lpe@odoo.com>
Co-authored-by: Sébastien Theys <seb@odoo.com>
Co-authored-by: Xavier Dubuc <xdu@odoo.com>

11 files changed, 1379 insertions, 0 deletions

diff --git a/addons/snailmail/static/src/components/message/message.js b/addons/snailmail/static/src/components/message/message.js
new file mode 100644
index 00000000000..1033c901367
--- /dev/null
+++ b/addons/snailmail/static/src/components/message/message.js
@@ -0,0 +1,87 @@
+odoo.define('snailmail/static/src/components/message/message.js', function (require) {
+'use strict';
+
+const components = {
+    Message: require('mail/static/src/components/message/message.js'),
+    SnailmailErrorDialog: require('snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.js'),
+    SnailmailNotificationPopover: require('snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.js'),
+};
+
+const { patch } = require('web.utils');
+
+const { useState } = owl;
+
+Object.assign(components.Message.components, {
+    SnailmailErrorDialog: components.SnailmailErrorDialog,
+    SnailmailNotificationPopover: components.SnailmailNotificationPopover,
+});
+
+patch(components.Message, 'snailmail/static/src/components/message/message.js', {
+    /**
+     * @override
+     */
+    _constructor() {
+        this._super(...arguments);
+        this.snailmailState = useState({
+            // Determine if the error dialog is displayed.
+            hasDialog: false,
+        });
+    },
+
+    //--------------------------------------------------------------------------
+    // Handlers
+    //--------------------------------------------------------------------------
+
+    /**
+     * @override
+     */
+    _onClickFailure() {
+        if (this.message.message_type === 'snailmail') {
+            /**
+             * Messages from snailmail are considered to have at most one
+             * notification. The failure type of the whole message is considered
+             * to be the same as the one from that first notification, and the
+             * click action will depend on it.
+             */
+            switch (this.message.notifications[0].failure_type) {
+                case 'sn_credit':
+                    // URL only used in this component, not received at init
+                    this.env.messaging.fetchSnailmailCreditsUrl();
+                    this.snailmailState.hasDialog = true;
+                    break;
+                case 'sn_error':
+                    this.snailmailState.hasDialog = true;
+                    break;
+                case 'sn_fields':
+                    this.message.openMissingFieldsLetterAction();
+                    break;
+                case 'sn_format':
+                    this.message.openFormatLetterAction();
+                    break;
+                case 'sn_price':
+                    this.snailmailState.hasDialog = true;
+                    break;
+                case 'sn_trial':
+                    // URL only used in this component, not received at init
+                    this.env.messaging.fetchSnailmailCreditsUrlTrial();
+                    this.snailmailState.hasDialog = true;
+                    break;
+            }
+        } else {
+            this._super(...arguments);
+        }
+    },
+
+    //--------------------------------------------------------------------------
+    // Handlers
+    //--------------------------------------------------------------------------
+
+    /**
+     * @private
+     */
+    _onDialogClosedSnailmailError() {
+        this.snailmailState.hasDialog = false;
+    },
+});
+
+});
diff --git a/addons/snailmail/static/src/components/message/message.xml b/addons/snailmail/static/src/components/message/message.xml
new file mode 100644
index 00000000000..d563083fc15
--- /dev/null
+++ b/addons/snailmail/static/src/components/message/message.xml
@@ -0,0 +1,37 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<templates xml:space="preserve">
+
+    <t t-inherit="mail.Message" t-inherit-mode="extension">
+        <xpath expr="//*[@name='failureIcon']" position="replace">
+            <t t-if="message.message_type === 'snailmail'">
+                <i class="o_Message_notificationIcon fa fa-paper-plane"/>
+            </t>
+            <t t-else="">$0</t>
+        </xpath>
+
+        <xpath expr="//*[@name='notificationIcon']" position="replace">
+            <t t-if="message.message_type === 'snailmail'">
+                <i class="o_Message_notificationIcon fa fa-paper-plane"/>
+            </t>
+            <t t-else="">$0</t>
+        </xpath>
+
+        <xpath expr="//*[@name='rootCondition']" position="inside">
+            <t t-if="snailmailState.hasDialog">
+                <SnailmailErrorDialog messageLocalId="message.localId" t-on-dialog-closed="_onDialogClosedSnailmailError"/>
+            </t>
+        </xpath>
+
+        <!--
+            It was decided that the information displayed for snailmail messages
+            has to be different than for standard messages, see task-1907998.
+        -->
+        <xpath expr="//NotificationPopover" position="replace">
+            <t t-if="message.message_type === 'snailmail'">
+                <SnailmailNotificationPopover messageLocalId="message.localId"/>
+            </t>
+            <t t-else="">$0</t>
+        </xpath>
+    </t>
+
+</templates>
diff --git a/addons/snailmail/static/src/components/message/message_tests.js b/addons/snailmail/static/src/components/message/message_tests.js
new file mode 100644
index 00000000000..10f917b2bbe
--- /dev/null
+++ b/addons/snailmail/static/src/components/message/message_tests.js
@@ -0,0 +1,624 @@
+odoo.define('snailmail/static/src/components/message/message_tests.js', function (require) {
+'use strict';
+
+const components = {
+    Message: require('mail/static/src/components/message/message.js'),
+};
+const {
+    afterEach: utilsAfterEach,
+    afterNextRender,
+    beforeEach: utilsBeforeEach,
+    start: utilsStart,
+} = require('mail/static/src/utils/test_utils.js');
+
+const Bus = require('web.Bus');
+
+QUnit.module('snailmail', {}, function () {
+QUnit.module('components', {}, function () {
+QUnit.module('message', {}, function () {
+QUnit.module('message_tests.js', {
+    beforeEach() {
+        utilsBeforeEach(this);
+
+        this.createMessageComponent = async message => {
+            const MessageComponent = components.Message;
+            MessageComponent.env = this.env;
+            this.component = new MessageComponent(null, {
+                messageLocalId: message.localId,
+            });
+            delete MessageComponent.env;
+            await this.component.mount(this.widget.el);
+        };
+
+        this.start = async params => {
+            let { env, widget } = await utilsStart(Object.assign({}, params, {
+                data: this.data,
+            }));
+            this.env = env;
+            this.widget = widget;
+        };
+    },
+    afterEach() {
+        utilsAfterEach(this);
+        if (this.component) {
+            // The component must be destroyed before the widget, because the
+            // widget might destroy the models before destroying the component,
+            // and the Message component is relying on messaging.
+            this.component.destroy();
+        }
+        if (this.widget) {
+            this.widget.destroy();
+        }
+        this.env = undefined;
+    },
+});
+
+QUnit.test('Sent', async function (assert) {
+    assert.expect(8);
+
+    await this.start();
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            id: 11,
+            notification_status: 'sent',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailNotificationPopover',
+        "notification popover should be open"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailNotificationPopover_icon',
+        "popover should have one icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_SnailmailNotificationPopover_icon'),
+        'fa-check',
+        "popover should have the sent icon"
+    );
+    assert.strictEqual(
+        document.querySelector('.o_SnailmailNotificationPopover').textContent.trim(),
+        "Sent",
+        "popover should have the sent text"
+    );
+});
+
+QUnit.test('Canceled', async function (assert) {
+    assert.expect(8);
+
+    await this.start();
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            id: 11,
+            notification_status: 'canceled',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailNotificationPopover',
+        "notification popover should be open"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailNotificationPopover_icon',
+        "popover should have one icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_SnailmailNotificationPopover_icon'),
+        'fa-trash-o',
+        "popover should have the canceled icon"
+    );
+    assert.strictEqual(
+        document.querySelector('.o_SnailmailNotificationPopover').textContent.trim(),
+        "Canceled",
+        "popover should have the canceled text"
+    );
+});
+
+QUnit.test('Pending', async function (assert) {
+    assert.expect(8);
+
+    await this.start();
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            id: 11,
+            notification_status: 'ready',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailNotificationPopover',
+        "notification popover should be open"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailNotificationPopover_icon',
+        "popover should have one icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_SnailmailNotificationPopover_icon'),
+        'fa-clock-o',
+        "popover should have the pending icon"
+    );
+    assert.strictEqual(
+        document.querySelector('.o_SnailmailNotificationPopover').textContent.trim(),
+        "Awaiting Dispatch",
+        "popover should have the pending text"
+    );
+});
+
+QUnit.test('No Price Available', async function (assert) {
+    assert.expect(10);
+
+    await this.start({
+        async mockRPC(route, args) {
+            if (args.method === 'cancel_letter' && args.model === 'mail.message' && args.args[0][0] === 10) {
+                assert.step(args.method);
+                return;
+            }
+            return this._super(...arguments);
+        },
+    });
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            failure_type: 'sn_price',
+            id: 11,
+            notification_status: 'exception',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog',
+        "error dialog should be open"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_contentPrice',
+        "error dialog should have the 'no price' content"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_cancelLetterButton',
+        "dialog should have a 'Cancel letter' button"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_SnailmailErrorDialog_cancelLetterButton').click();
+    });
+    assert.containsNone(
+        document.body,
+        '.o_SnailmailErrorDialog',
+        "dialog should be closed after click on 'Cancel letter'"
+    );
+    assert.verifySteps(
+        ['cancel_letter'],
+        "should have made a RPC call to 'cancel_letter'"
+    );
+});
+
+QUnit.test('Credit Error', async function (assert) {
+    assert.expect(11);
+
+    await this.start({
+        async mockRPC(route, args) {
+            if (args.method === 'send_letter' && args.model === 'mail.message' && args.args[0][0] === 10) {
+                assert.step(args.method);
+                return;
+            }
+            if (args.method === 'get_credits_url') {
+                return 'credits_url';
+            }
+            return this._super(...arguments);
+        },
+    });
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            failure_type: 'sn_credit',
+            id: 11,
+            notification_status: 'exception',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog',
+        "error dialog should be open"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_contentCredit',
+        "error dialog should have the 'credit' content"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_resendLetterButton',
+        "dialog should have a 'Re-send letter' button"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_cancelLetterButton',
+        "dialog should have a 'Cancel letter' button"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_SnailmailErrorDialog_resendLetterButton').click();
+    });
+    assert.containsNone(
+        document.body,
+        '.o_SnailmailErrorDialog',
+        "dialog should be closed after click on 'Re-send letter'"
+    );
+    assert.verifySteps(
+        ['send_letter'],
+        "should have made a RPC call to 'send_letter'"
+    );
+});
+
+QUnit.test('Trial Error', async function (assert) {
+    assert.expect(11);
+
+    await this.start({
+        async mockRPC(route, args) {
+            if (args.method === 'send_letter' && args.model === 'mail.message' && args.args[0][0] === 10) {
+                assert.step(args.method);
+                return;
+            }
+            if (args.method === 'get_credits_url') {
+                return 'credits_url_trial';
+            }
+            return this._super(...arguments);
+        },
+    });
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            failure_type: 'sn_trial',
+            id: 11,
+            notification_status: 'exception',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog',
+        "error dialog should be open"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_contentTrial',
+        "error dialog should have the 'trial' content"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_resendLetterButton',
+        "dialog should have a 'Re-send letter' button"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_SnailmailErrorDialog_cancelLetterButton',
+        "dialog should have a 'Cancel letter' button"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_SnailmailErrorDialog_resendLetterButton').click();
+    });
+    assert.containsNone(
+        document.body,
+        '.o_SnailmailErrorDialog',
+        "dialog should be closed after click on 'Re-send letter'"
+    );
+    assert.verifySteps(
+        ['send_letter'],
+        "should have made a RPC call to 'send_letter'"
+    );
+});
+
+QUnit.test('Format Error', async function (assert) {
+    assert.expect(8);
+
+    const bus = new Bus();
+    bus.on('do-action', null, payload => {
+        assert.step('do_action');
+        assert.strictEqual(
+            payload.action,
+            'snailmail.snailmail_letter_format_error_action',
+            "action should be the one for format error"
+        );
+        assert.strictEqual(
+            payload.options.additional_context.message_id,
+            10,
+            "action should have correct message id"
+        );
+    });
+
+    await this.start({ env: { bus } });
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            failure_type: 'sn_format',
+            id: 11,
+            notification_status: 'exception',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.verifySteps(
+        ['do_action'],
+        "should do an action to display the format error dialog"
+    );
+});
+
+QUnit.test('Missing Required Fields', async function (assert) {
+    assert.expect(9);
+
+    const bus = new Bus();
+    bus.on('do-action', null, payload => {
+        assert.step('do_action');
+        assert.strictEqual(
+            payload.action,
+            'snailmail.snailmail_letter_missing_required_fields_action',
+            "action should be the one for missing fields"
+        );
+        assert.strictEqual(
+            payload.options.additional_context.letter_id,
+            22, // should be the same as the id returned by search
+            "action should have correct letter id"
+        );
+    });
+
+    await this.start({
+        env: { bus },
+        async mockRPC(route, args) {
+            if (args.model === 'snailmail.letter' && args.method === 'search') {
+                assert.step('search');
+                return [22]; // should be the same as the id given to the action
+            }
+            return this._super(...arguments);
+        },
+    });
+    const message = this.env.models['mail.message'].create({
+        id: 10,
+        message_type: 'snailmail',
+        notifications: [['insert', {
+            failure_type: 'sn_fields',
+            id: 11,
+            notification_status: 'exception',
+            notification_type: 'snail',
+        }]],
+    });
+    await this.createMessageComponent(message);
+
+    assert.containsOnce(
+        document.body,
+        '.o_Message',
+        "should display a message component"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIconContainer',
+        "should display the notification icon container"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_Message_notificationIcon',
+        "should display the notification icon"
+    );
+    assert.hasClass(
+        document.querySelector('.o_Message_notificationIcon'),
+        'fa-paper-plane',
+        "icon should represent snailmail"
+    );
+
+    await afterNextRender(() => {
+        document.querySelector('.o_Message_notificationIconContainer').click();
+    });
+    assert.verifySteps(
+        ['search', 'do_action'],
+        "the id of the letter related to the message should be returned by a search and an action should be done to display the missing fields dialog"
+    );
+});
+
+});
+});
+});
+
+});
diff --git a/addons/snailmail/static/src/components/notification_group/notification_group.js b/addons/snailmail/static/src/components/notification_group/notification_group.js
new file mode 100644
index 00000000000..00cdebe15d9
--- /dev/null
+++ b/addons/snailmail/static/src/components/notification_group/notification_group.js
@@ -0,0 +1,27 @@
+odoo.define('snailmail/static/src/components/notification_group/notification_group.js', function (require) {
+'use strict';
+
+const components = {
+    NotificationGroup: require('mail/static/src/components/notification_group/notification_group.js'),
+};
+
+const { patch } = require('web.utils');
+
+patch(components.NotificationGroup, 'snailmail/static/src/components/notification_group/notification_group.js', {
+
+    //--------------------------------------------------------------------------
+    // Public
+    //--------------------------------------------------------------------------
+
+    /**
+     * @override
+     */
+    image() {
+        if (this.group.notification_type === 'snail') {
+            return '/snailmail/static/img/snailmail_failure.png';
+        }
+        return this._super(...arguments);
+    },
+});
+
+});
diff --git a/addons/snailmail/static/src/components/notification_group/notification_group.xml b/addons/snailmail/static/src/components/notification_group/notification_group.xml
new file mode 100644
index 00000000000..7f04e716072
--- /dev/null
+++ b/addons/snailmail/static/src/components/notification_group/notification_group.xml
@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<templates xml:space="preserve">
+
+    <t t-inherit="mail.NotificationGroup" t-inherit-mode="extension">
+        <xpath expr="//*[hasclass('o_NotificationGroup_inlineText')]" position="inside">
+            <t t-if="group.notification_type === 'snail'">
+                An error occurred when sending a letter with Snailmail.
+            </t>
+        </xpath>
+    </t>
+
+</templates>
diff --git a/addons/snailmail/static/src/components/notification_list/notification_list_notification_group_tests.js b/addons/snailmail/static/src/components/notification_list/notification_list_notification_group_tests.js
new file mode 100644
index 00000000000..18844086473
--- /dev/null
+++ b/addons/snailmail/static/src/components/notification_list/notification_list_notification_group_tests.js
@@ -0,0 +1,312 @@
+odoo.define('snailmail/static/src/components/notification_list/notification_list_notification_group_tests.js', function (require) {
+'use strict';
+
+const components = {
+    NotificationList: require('mail/static/src/components/notification_list/notification_list.js'),
+};
+
+const {
+    afterEach: utilsAfterEach,
+    afterNextRender,
+    beforeEach: utilsBeforeEach,
+    start: utilsStart,
+} = require('mail/static/src/utils/test_utils.js');
+
+const Bus = require('web.Bus');
+
+QUnit.module('snailmail', {}, function () {
+QUnit.module('components', {}, function () {
+QUnit.module('notification_list', {}, function () {
+QUnit.module('notification_list_notification_group_tests.js', {
+    beforeEach() {
+        utilsBeforeEach(this);
+
+        /**
+         * @param {Object} param0
+         * @param {string} [param0.filter='all']
+         */
+        this.createNotificationListComponent = async ({ filter = 'all' } = {}) => {
+            const NotificationListComponent = components.NotificationList;
+            NotificationListComponent.env = this.env;
+            this.component = new NotificationListComponent(null, { filter });
+            await afterNextRender(() => this.component.mount(this.widget.el));
+        };
+
+        this.start = async params => {
+            let { env, widget } = await utilsStart(Object.assign({}, params, {
+                data: this.data,
+            }));
+            this.env = env;
+            this.widget = widget;
+        };
+    },
+    afterEach() {
+        utilsAfterEach(this);
+        if (this.component) {
+            this.component.destroy();
+            this.component = undefined;
+        }
+        if (this.widget) {
+            this.widget.destroy();
+            this.widget = undefined;
+        }
+        this.env = undefined;
+        delete components.NotificationList.env;
+    },
+});
+
+QUnit.test('mark as read', async function (assert) {
+    assert.expect(6);
+
+    this.data.initMessaging.mail_failures = [{
+        date: moment.utc().format("YYYY-MM-DD HH:mm:ss"),
+        id: 11,
+        message_type: 'snailmail',
+        model: 'mail.channel',
+        notifications: [{
+            failure_type: 'sn_credit',
+            id: 21,
+            notification_status: 'exception',
+            notification_type: 'snail',
+            partner_id: [41, "Someone"],
+        }],
+        res_id: 31,
+        res_model_name: "Channel",
+    }];
+    const bus = new Bus();
+    bus.on('do-action', null, payload => {
+        assert.step('do_action');
+        assert.strictEqual(
+            payload.action,
+            'snailmail.snailmail_letter_cancel_action',
+            "action should be the one to cancel letter"
+        );
+        assert.strictEqual(
+            payload.options.additional_context.default_model,
+            'mail.channel',
+            "action should have the group model as default_model"
+        );
+        assert.strictEqual(
+            payload.options.additional_context.unread_counter,
+            1,
+            "action should have the group notification length as unread_counter"
+        );
+    });
+
+    await this.start({ env: { bus } });
+    await this.createNotificationListComponent();
+
+    assert.containsOnce(
+        document.body,
+        '.o_NotificationGroup_markAsRead',
+        "should have 1 mark as read button"
+    );
+
+    document.querySelector('.o_NotificationGroup_markAsRead').click();
+    assert.verifySteps(
+        ['do_action'],
+        "should do an action to display the cancel letter dialog"
+    );
+});
+
+QUnit.test('notifications grouped by notification_type', async function (assert) {
+    assert.expect(11);
+
+    this.data.initMessaging.mail_failures = [{
+        date: moment.utc().format("YYYY-MM-DD HH:mm:ss"),
+        id: 11,
+        message_type: 'email', // key element of this test: different type
+        model: 'res.partner', // key element of this test: same model (and not `mail.channel``)
+        notifications: [{
+            failure_type: 'SMTP',
+            id: 21,
+            notification_status: 'exception',
+            notification_type: 'email', // key element of this test: different type
+            partner_id: [41, "Someone"],
+        }],
+        res_id: 31, // key element of this test: same res_id
+        res_model_name: "Partner",
+    }, {
+        date: moment.utc().format("YYYY-MM-DD HH:mm:ss"),
+        id: 12,
+        message_type: 'snailmail', // key element of this test: different type
+        model: 'res.partner', // key element of this test: same model (and not `mail.channel``)
+        notifications: [{
+            failure_type: 'sn_credit',
+            id: 22,
+            notification_status: 'exception',
+            notification_type: 'snail', // key element of this test: different type
+            partner_id: [42, "Someone else"],
+        }],
+        res_id: 31, // key element of this test: same res_id
+        res_model_name: "Partner",
+    }];
+
+    await this.start();
+    await this.createNotificationListComponent();
+
+    assert.containsN(
+        document.body,
+        '.o_NotificationGroup',
+        2,
+        "should have 2 notifications group"
+    );
+    const groups = document.querySelectorAll('.o_NotificationGroup');
+    assert.containsOnce(
+        groups[0],
+        '.o_NotificationGroup_name',
+        "should have 1 group name in first group"
+    );
+    assert.strictEqual(
+        groups[0].querySelector('.o_NotificationGroup_name').textContent,
+        "Partner",
+        "should have model name as group name"
+    );
+    assert.containsOnce(
+        groups[0],
+        '.o_NotificationGroup_counter',
+        "should have 1 group counter in first group"
+    );
+    assert.strictEqual(
+        groups[0].querySelector('.o_NotificationGroup_counter').textContent.trim(),
+        "(1)",
+        "should have 1 notification in first group"
+    );
+    assert.strictEqual(
+        groups[0].querySelector('.o_NotificationGroup_inlineText').textContent.trim(),
+        "An error occurred when sending an email.",
+        "should have the group text corresponding to email"
+    );
+    assert.containsOnce(
+        groups[1],
+        '.o_NotificationGroup_name',
+        "should have 1 group name in second group"
+    );
+    assert.strictEqual(
+        groups[1].querySelector('.o_NotificationGroup_name').textContent,
+        "Partner",
+        "should have second model name as group name"
+    );
+    assert.containsOnce(
+        groups[1],
+        '.o_NotificationGroup_counter',
+        "should have 1 group counter in second group"
+    );
+    assert.strictEqual(
+        groups[1].querySelector('.o_NotificationGroup_counter').textContent.trim(),
+        "(1)",
+        "should have 1 notification in second group"
+    );
+    assert.strictEqual(
+        groups[1].querySelector('.o_NotificationGroup_inlineText').textContent.trim(),
+        "An error occurred when sending a letter with Snailmail.",
+        "should have the group text corresponding to snailmail"
+    );
+});
+
+QUnit.test('grouped notifications by document model', async function (assert) {
+    // If all failures linked to a document model refers to different documents,
+    // a single notification should group all failures that are linked to this
+    // document model.
+    assert.expect(12);
+
+    this.data.initMessaging.mail_failures = [{
+        date: moment.utc().format("YYYY-MM-DD HH:mm:ss"),
+        id: 11,
+        message_type: 'snailmail',
+        model: 'res.partner', // key element of this test: same model
+        notifications: [{
+            failure_type: 'sn_credit',
+            id: 21,
+            notification_status: 'exception',
+            notification_type: 'snail',
+            partner_id: [41, "Someone"],
+        }],
+        res_id: 31, // key element of this test: a different res_id
+        res_model_name: "Partner",
+    }, {
+        date: moment.utc().format("YYYY-MM-DD HH:mm:ss"),
+        id: 12,
+        message_type: 'snailmail',
+        model: 'res.partner', // key element of this test: same model
+        notifications: [{
+            failure_type: 'sn_credit',
+            id: 22,
+            notification_status: 'exception',
+            notification_type: 'snail',
+            partner_id: [42, "Someone else"],
+        }],
+        res_id: 32, // key element of this test: a different res_id
+        res_model_name: "Partner",
+    }];
+    const bus = new Bus();
+    bus.on('do-action', null, payload => {
+        assert.step('do_action');
+        assert.strictEqual(
+            payload.action.name,
+            "Snailmail Failures",
+            "action should have 'Snailmail Failures' as name",
+        );
+        assert.strictEqual(
+            payload.action.type,
+            'ir.actions.act_window',
+            "action should have the type act_window"
+        );
+        assert.strictEqual(
+            payload.action.view_mode,
+            'kanban,list,form',
+            "action should have 'kanban,list,form' as view_mode"
+        );
+        assert.strictEqual(
+            JSON.stringify(payload.action.views),
+            JSON.stringify([[false, 'kanban'], [false, 'list'], [false, 'form']]),
+            "action should have correct views"
+        );
+        assert.strictEqual(
+            payload.action.target,
+            'current',
+            "action should have 'current' as target"
+        );
+        assert.strictEqual(
+            payload.action.res_model,
+            'res.partner',
+            "action should have the group model as res_model"
+        );
+        assert.strictEqual(
+            JSON.stringify(payload.action.domain),
+            JSON.stringify([['message_ids.snailmail_error', '=', true]]),
+            "action should have 'message_has_sms_error' as domain"
+        );
+    });
+
+    await this.start({ env: { bus } });
+    await this.createNotificationListComponent();
+
+    assert.containsOnce(
+        document.body,
+        '.o_NotificationGroup',
+        "should have 1 notification group"
+    );
+    assert.containsOnce(
+        document.body,
+        '.o_NotificationGroup_counter',
+        "should have 1 group counter"
+    );
+    assert.strictEqual(
+        document.querySelector('.o_NotificationGroup_counter').textContent.trim(),
+        "(2)",
+        "should have 2 notifications in the group"
+    );
+
+    document.querySelector('.o_NotificationGroup').click();
+    assert.verifySteps(
+        ['do_action'],
+        "should do an action to display the related records"
+    );
+});
+
+});
+});
+});
+
+});
diff --git a/addons/snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.js b/addons/snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.js
new file mode 100644
index 00000000000..a7daf7c1091
--- /dev/null
+++ b/addons/snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.js
@@ -0,0 +1,113 @@
+odoo.define('snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.js', function (require) {
+'use strict';
+
+const useStore = require('mail/static/src/component_hooks/use_store/use_store.js');
+
+const Dialog = require('web.OwlDialog');
+
+const { Component } = owl;
+const { useRef } = owl.hooks;
+
+class SnailmailErrorDialog extends Component {
+
+    /**
+     * @override
+     */
+    constructor(...args) {
+        super(...args);
+        useStore(props => {
+            const message = this.env.models['mail.message'].get(props.messageLocalId);
+            const notifications = message ? message.notifications : [];
+            return {
+                message: message ? message.__state : undefined,
+                notifications: notifications.map(notification =>
+                    notification ? notification.__state : undefined
+                ),
+                snailmail_credits_url: this.env.messaging.snailmail_credits_url,
+                snailmail_credits_url_trial: this.env.messaging.snailmail_credits_url_trial,
+            };
+        }, {
+            compareDepth: {
+                notifications: 1,
+            },
+        });
+        // to manually trigger the dialog close event
+        this._dialogRef = useRef('dialog');
+    }
+
+    //--------------------------------------------------------------------------
+    // Public
+    //--------------------------------------------------------------------------
+
+    /**
+     * @returns {boolean}
+     */
+    get hasCreditsError() {
+        return (
+            this.notification.failure_type === 'sn_credit' ||
+            this.notification.failure_type === 'sn_trial'
+        );
+    }
+
+    /**
+     * @returns {mail.message}
+     */
+    get message() {
+        return this.env.models['mail.message'].get(this.props.messageLocalId);
+    }
+
+    /**
+     * @returns {mail.notification}
+     */
+    get notification() {
+        // Messages from snailmail are considered to have at most one notification.
+        return this.message.notifications[0];
+    }
+
+    /**
+     * @returns {string}
+     */
+    get title() {
+        return this.env._t("Failed letter");
+    }
+
+    //--------------------------------------------------------------------------
+    // Handlers
+    //--------------------------------------------------------------------------
+
+    /**
+     * @private
+     */
+    _onClickCancelLetter() {
+        this._dialogRef.comp._close();
+        this.message.cancelLetter();
+    }
+
+    /**
+     * @private
+     */
+    _onClickClose() {
+        this._dialogRef.comp._close();
+    }
+
+    /**
+     * @private
+     */
+    _onClickResendLetter() {
+        this._dialogRef.comp._close();
+        this.message.resendLetter();
+    }
+
+}
+
+Object.assign(SnailmailErrorDialog, {
+    components: { Dialog },
+    props: {
+        messageLocalId: String,
+    },
+    template: 'snailmail.SnailmailErrorDialog',
+});
+
+return SnailmailErrorDialog;
+
+});
diff --git a/addons/snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.xml b/addons/snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.xml
new file mode 100644
index 00000000000..bf4f026e6d5
--- /dev/null
+++ b/addons/snailmail/static/src/components/snailmail_error_dialog/snailmail_error_dialog.xml
@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<templates xml:space="preserve">
+
+    <t t-name="snailmail.SnailmailErrorDialog" owl="1">
+        <Dialog contentClass="'o_SnailmailErrorDialog'" title="title" size="'medium'" t-ref="dialog">
+            <t t-if="message and notification">
+                <t t-if="notification.failure_type === 'sn_credit'">
+                    <p class="o_SnailmailErrorDialog_contentCredit">
+                        The letter could not be sent due to insufficient credits on your IAP account.
+                    </p>
+                    <t t-if="env.messaging.snailmail_credits_url">
+                        <div class="text-right">
+                            <a class="btn btn-link" t-att-href="env.messaging.snailmail_credits_url" target="_blank">
+                                <i class="fa fa-arrow-right"/> Buy credits
+                            </a>
+                        </div>
+                    </t>
+                </t>
+                <t t-elif="notification.failure_type === 'sn_trial'">
+                    <p class="o_SnailmailErrorDialog_contentTrial">
+                        You need credits on your IAP account to send a letter.
+                    </p>
+                    <t t-if="env.messaging.snailmail_credits_url_trial">
+                        <div class="text-right">
+                            <a class="btn btn-link" t-att-href="env.messaging.snailmail_credits_url_trial">
+                                <i class="fa fa-arrow-right"/> Buy credits
+                            </a>
+                        </div>
+                    </t>
+                </t>
+                <t t-elif="notification.failure_type === 'sn_price'">
+                    <p class="o_SnailmailErrorDialog_contentPrice">
+                        The country to which you want to send the letter is not supported by our service.
+                    </p>
+                </t>
+                <t t-elif="notification.failure_type === 'sn_error'">
+                    <p class="o_SnailmailErrorDialog_contentError">
+                        An unknown error occurred. Please contact our <a href="https://www.odoo.com/help" target="new">support</a> for further assistance.
+                    </p>
+                </t>
+
+                <t t-set-slot="buttons">
+                    <t t-if="hasCreditsError">
+                        <button class="o_SnailmailErrorDialog_resendLetterButton btn btn-primary" t-on-click="_onClickResendLetter">Re-send letter</button>
+                    </t>
+                    <button class="o_SnailmailErrorDialog_cancelLetterButton btn"
+                        t-att-class="{
+                            'btn-primary': !hasCreditsError,
+                            'btn-secondary': hasCreditsError,
+                        }"
+                        t-on-click="_onClickCancelLetter"
+                    >
+                        Cancel letter
+                    </button>
+                    <button class="o_SnailmailErrorDialog_closeButton btn btn-secondary" t-on-click="_onClickClose">Close</button>
+                </t>
+            </t>
+        </Dialog>
+    </t>
+
+</templates>
diff --git a/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.js b/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.js
new file mode 100644
index 00000000000..0845ce07818
--- /dev/null
+++ b/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.js
@@ -0,0 +1,86 @@
+odoo.define('snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.js', function (require) {
+'use strict';
+
+const { Component } = owl;
+const useStore = require('mail/static/src/component_hooks/use_store/use_store.js');
+
+class SnailmailNotificationPopover extends Component {
+
+    /**
+     * @override
+     */
+    constructor(...args) {
+        super(...args);
+        useStore(props => {
+            const message = this.env.models['mail.message'].get(props.messageLocalId);
+            const notifications = message ? message.notifications : [];
+            return {
+                message: message ? message.__state : undefined,
+                notifications: notifications.map(notification => notification ? notification.__state : undefined),
+            };
+        }, {
+            compareDepth: {
+                notifications: 1,
+            },
+        });
+    }
+
+    /**
+     * @returns {string}
+     */
+    get iconClass() {
+        switch (this.notification.notification_status) {
+            case 'sent':
+                return 'fa fa-check';
+            case 'ready':
+                return 'fa fa-clock-o';
+            case 'canceled':
+                return 'fa fa-trash-o';
+            default:
+                return 'fa fa-exclamation text-danger';
+        }
+    }
+
+    /**
+     * @returns {string}
+     */
+    get iconTitle() {
+        switch (this.notification.notification_status) {
+            case 'sent':
+                return this.env._t("Sent");
+            case 'ready':
+                return this.env._t("Awaiting Dispatch");
+            case 'canceled':
+                return this.env._t("Canceled");
+            default:
+                return this.env._t("Error");
+        }
+    }
+
+    /**
+     * @returns {mail.message}
+     */
+    get message() {
+        return this.env.models['mail.message'].get(this.props.messageLocalId);
+    }
+
+    /**
+     * @returns {mail.notification}
+     */
+    get notification() {
+        // Messages from snailmail are considered to have at most one notification.
+        return this.message.notifications[0];
+    }
+
+}
+
+Object.assign(SnailmailNotificationPopover, {
+    props: {
+        messageLocalId: String,
+    },
+    template: 'snailmail.SnailmailNotificationPopover',
+});
+
+return SnailmailNotificationPopover;
+
+});
diff --git a/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.scss b/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.scss
new file mode 100644
index 00000000000..970bc79d997
--- /dev/null
+++ b/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.scss
@@ -0,0 +1,7 @@
+// -----------------------------------------------------------------------------
+// Layout
+// -----------------------------------------------------------------------------
+
+.o_SnailmailNotificationPopover_icon {
+    margin-inline-end: map-get($spacers, 2);
+}
diff --git a/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.xml b/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.xml
new file mode 100644
index 00000000000..873b08f4d37
--- /dev/null
+++ b/addons/snailmail/static/src/components/snailmail_notification_popover/snailmail_notification_popover.xml
@@ -0,0 +1,13 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<templates xml:space="preserve">
+
+    <t t-name="snailmail.SnailmailNotificationPopover" owl="1">
+        <div class="o_SnailmailNotificationPopover">
+            <t t-if="message and notification">
+                <i class="o_SnailmailNotificationPopover_icon" t-att-class="iconClass" role="img"/>
+                <span t-esc="iconTitle"/>
+            </t>
+        </div>
+    </t>
+
+</templates>