[MM-23082] Fixes whitescreen issue on app upgrade / GPO / whitelabeled app deployments (#1246)

* Fixes whitescreen issue on app upgrade / GPO push / whitelabeled app deployments.  If sort order was not present in buildConfig.js (or previous configuration), we will assume reasonable defaults

* Fixing eslint bugs - with my apologies

* Removing order flag from sample configuration, but leaving it in the documentation.
BUGFIX: Accidentally left my custom enableServerManagement flag in place.  Reverted to default

* Making a more educated guess as to the user's desired sort order.

* Update src/common/config/index.js

Use forEach's index instead of an external one.

Co-Authored-By: Guillermo Vayá <guivaya@gmail.com>

* Update src/common/config/index.js

Let me test this, I'm not sure I understand how this logic works.  :)

Co-Authored-By: Guillermo Vayá <guivaya@gmail.com>

* Removed optional field

* Fixed broken lint:js with my apologies

Co-authored-by: Guillermo Vayá <guivaya@gmail.com>

src/common/config/buildConfig.js

@@ -9,6 +9,7 @@
  * @prop {Object[]} defaultTeams
  * @prop {string} defaultTeams[].name - The tab name for default team.
  * @prop {string} defaultTeams[].url - The URL for default team.
+ * @prop {string} defaultTeams[].order - Sort order for team tabs (0, 1, 2)
  * @prop {string} helpLink - The URL for "Help->Learn More..." menu item.
  *                           If null is specified, the menu disappears.
  * @prop {boolean} enableServerManagement - Whether users can edit servers configuration.
@@ -20,8 +21,8 @@ const buildConfig = {
     {
       name: 'example',
       url: 'https://example.com'
-    }*/
+    }
-  ],
+  */],
   helpLink: 'https://about.mattermost.com/default-desktop-app-documentation/',
   enableServerManagement: true,
   enableAutoUpdater: true,

src/common/config/index.js

@@ -272,7 +272,7 @@ export default class Config extends EventEmitter {
     delete this.combinedData.defaultTeams;
 
     // IMPORTANT: properly combine teams from all sources
-    const combinedTeams = [];
+    let combinedTeams = [];
 
     // - start by adding default teams from buildConfig, if any
     if (this.buildConfigData.defaultTeams && this.buildConfigData.defaultTeams.length) {
@@ -289,6 +289,9 @@ export default class Config extends EventEmitter {
       combinedTeams.push(...this.localConfigData.teams);
     }
 
+    combinedTeams = this.filterOutDuplicateTeams(combinedTeams);
+    combinedTeams = this.sortUnorderedTeams(combinedTeams);
+
     this.combinedData.teams = combinedTeams;
     this.combinedData.localTeams = this.localConfigData.teams;
     this.combinedData.buildTeams = this.buildConfigData.defaultTeams;
@@ -324,6 +327,35 @@ export default class Config extends EventEmitter {
     return newTeams;
   }
 
+  /**
+   * Apply a default sort order to the team list, if no order is specified.
+   * @param {array} teams to sort
+   */
+  sortUnorderedTeams(teams) {
+    // Make a best pass at interpreting sort order. If an order is not specified, assume it is 0.
+    //
+    const newTeams = teams.sort((x, y) => {
+      if (x.order == null) {
+        x.order = 0;
+      }
+      if (y.order == null) {
+        y.order = 0;
+      }
+
+      // once we ensured `order` exists, we can sort numerically
+      return x.order - y.order;
+    });
+
+    // Now re-number all items from 0 to (max), ensuring user's sort order is preserved. The
+    // new tabbed interface requires an item with order:0 in order to raise the first tab.
+    //
+    newTeams.forEach((team, i) => {
+      team.order = i;
+    });
+
+    return newTeams;
+  }
+
   // helper functions
 
   readFileSync(filePath) {