message_list_view: Move edited position conditionals to JS.

This adds three bools to message_container object which calculate bools
where the "(EDITED)" label should appear:

* `edited_in_left_col` -- when label appears in left column.
* `edited_alongside_sender` -- when label appears alongside sender info.
* `edited_status_msg` -- when label appears for a "/me" message.

We use the new bools and remove the complicated if else statements
from the templates for the "(EDITED)" label.

This also allows us to add a unit test to verify the logic.

frontend_tests/node_tests/message_list_view.js

@@ -46,6 +46,81 @@ set_global('rows', {
     },
 });
 
+run_test('msg_edited_vars', () => {
+    // This is a test to verify that only one of the three bools,
+    // `edited_in_left_col`, `edited_alongside_sender`, `edited_status_msg`
+    // is not false; Tests for three different kinds of messages:
+    //   * "/me" message
+    //   * message that includes sender
+    //   * message without sender
+
+    function build_message_context(message, message_context) {
+        if (message_context === undefined) {
+            message_context = {};
+        }
+        if (message === undefined) {
+            message = {};
+        }
+        message_context = _.defaults(message_context, {
+            include_sender: true,
+        });
+        message_context.msg = _.defaults(message, {
+            is_me_message: false,
+            last_edit_timestamp: _.uniqueId(),
+        });
+        return message_context;
+    }
+
+    function build_message_group(messages) {
+        return { message_containers: messages };
+    }
+
+    function build_list(message_groups) {
+        var list = new MessageListView(undefined, undefined, true);
+        list._message_groups = message_groups;
+        return list;
+    }
+
+    function assert_left_col(message_container) {
+        assert.equal(message_container.edited_in_left_col, true);
+        assert.equal(message_container.edited_alongside_sender, false);
+        assert.equal(message_container.edited_status_msg, false);
+    }
+
+    function assert_alongside_sender(message_container) {
+        assert.equal(message_container.edited_in_left_col, false);
+        assert.equal(message_container.edited_alongside_sender, true);
+        assert.equal(message_container.edited_status_msg, false);
+    }
+
+    function assert_status_msg(message_container) {
+        assert.equal(message_container.edited_in_left_col, false);
+        assert.equal(message_container.edited_alongside_sender, false);
+        assert.equal(message_container.edited_status_msg, true);
+    }
+
+    (function test_msg_edited_vars() {
+        var messages = [
+            build_message_context(),
+            build_message_context({}, { include_sender: false }),
+            build_message_context({ is_me_message: true, content: "<p>/me test</p>" }),
+        ];
+        var message_group = build_message_group(messages);
+        var list = build_list([message_group]);
+
+        _.each(messages, function (message_container) {
+            list._maybe_format_me_message(message_container);
+            list._add_msg_edited_vars(message_container);
+        });
+
+        var result = list._message_groups[0].message_containers;
+
+        assert_alongside_sender(result[0]);
+        assert_left_col(result[1]);
+        assert_status_msg(result[2]);
+    }());
+});
+
 run_test('merge_message_groups', () => {
     // MessageListView has lots of DOM code, so we are going to test the message
     // group mearging logic on its own.

static/js/message_list_view.js

@@ -201,9 +201,21 @@ MessageListView.prototype = {
     },
 
     _add_msg_edited_vars: function (message_container) {
+        // This adds variables to message_container object which calculate bools for
+        // checking position of "(EDITED)" label as well as the edited timestring
+        // The bools can be defined only when the message is edited
+        // (or when the `last_edit_timestr` is defined). The bools are:
+        //   * `edited_in_left_col`      -- when label appears in left column.
+        //   * `edited_alongside_sender` -- when label appears alongside sender info.
+        //   * `edited_status_msg`       -- when label appears for a "/me" message.
         var last_edit_timestr = this._get_msg_timestring(message_container);
+        var include_sender = message_container.include_sender;
+        var status_message = Boolean(message_container.status_message);
         if (last_edit_timestr !== undefined) {
             message_container.last_edit_timestr = last_edit_timestr;
+            message_container.edited_in_left_col = !include_sender;
+            message_container.edited_alongside_sender = include_sender && !status_message;
+            message_container.edited_status_msg = include_sender && status_message;
         }
     },
 
@@ -321,8 +333,6 @@ MessageListView.prototype = {
             message_container.sender_is_bot = people.sender_is_bot(message_container.msg);
             message_container.sender_is_guest = people.sender_is_guest(message_container.msg);
 
-            self._add_msg_edited_vars(message_container);
-
             message_container.small_avatar_url = people.small_avatar_url(message_container.msg);
             if (message_container.msg.stream) {
                 message_container.background_color =
@@ -331,6 +341,8 @@ MessageListView.prototype = {
 
             message_container.contains_mention = message_container.msg.mentioned;
             self._maybe_format_me_message(message_container);
+            // Once all other variables are updated
+            self._add_msg_edited_vars(message_container);
 
             prev = message_container;
         });
@@ -1153,8 +1165,8 @@ MessageListView.prototype = {
         var was_selected = this.list.selected_message() === message_container.msg;
 
         // Re-render just this one message
-        this._add_msg_edited_vars(message_container);
         this._maybe_format_me_message(message_container);
+        this._add_msg_edited_vars(message_container);
 
         // Make sure the right thing happens if the message was edited to mention us.
         message_container.contains_mention = message_container.msg.mentioned;

static/templates/me_message.handlebars

@@ -13,8 +13,8 @@
             {{{ status_message }}}
         </span>
 
-        {{#if_and last_edit_timestr include_sender}}
+        {{#if edited_status_msg}}
         {{partial "edited_notice"}}
-        {{/if_and}}
+        {{/if}}
     </span>
 </span>

static/templates/message_body.handlebars

@@ -27,11 +27,9 @@
         {{timestr}}
     </span>
 
-    {{#if_and last_edit_timestr include_sender}}
-        {{#unless status_message}}
-        {{partial "edited_notice"}}
-        {{/unless}}
-    {{/if_and}}
+    {{#if edited_alongside_sender}}
+    {{partial "edited_notice"}}
+    {{/if}}
 
     {{partial "message_controls"}}
 
@@ -41,10 +39,8 @@
 <div class="message_content rendered_markdown">{{#if use_match_properties}}{{{msg/match_content}}}{{else}}{{{msg/content}}}{{/if}}</div>
 {{/unless}}
 
-{{#if last_edit_timestr}}
-    {{#unless include_sender}}
-    {{partial "edited_notice"}}
-    {{/unless}}
+{{#if edited_in_left_col}}
+{{partial "edited_notice"}}
 {{/if}}
 
 <div class="message_edit">