DEV: allow positioning of nav items and allow selection

Previously we could not place extra nav items in a particular order.

This change introduces a new `before` attribute to addNavigationBarItem
with this attribute we can place a nav item before "top" or any other place.


Additionally this allows navigation items to force active state. In some
cases we may want an items that is simply a "filter" on latest using `?query_params`
when we do that we can "force" the filter active.

A concrete example is the assign plugin that adds a nav item for

Unassigned => `/c/cat-slug/l/latest?assigned=nobody&status=open`

If we did not force then latest would be selected even though the filter
is clicked.

app/assets/javascripts/discourse/components/navigation-item.js.es6

@@ -15,8 +15,11 @@ export default Component.extend(
     hidden: false,
     rerenderTriggers: ["content.count"],
 
-    @computed("content.filterMode", "filterMode")
+    @computed("content.filterMode", "filterMode", "content.active")
-    active(contentFilterMode, filterMode) {
+    active(contentFilterMode, filterMode, active) {
+      if (active !== undefined) {
+        return active;
+      }
       return (
         contentFilterMode === filterMode ||
         filterMode.indexOf(contentFilterMode) === 0

app/assets/javascripts/discourse/lib/plugin-api.js.es6

@@ -46,7 +46,7 @@ import { queryRegistry } from "discourse/widgets/widget";
 import Composer from "discourse/models/composer";
 
 // If you add any methods to the API ensure you bump up this number
-const PLUGIN_API_VERSION = "0.8.34";
+const PLUGIN_API_VERSION = "0.8.35";
 
 class PluginApi {
   constructor(version, container) {
@@ -736,7 +736,9 @@ class PluginApi {
    *   displayName: "bugs"
    *   href: "/c/bugs",
    *   customFilter: (category, args, router) => { category && category.name !== 'bug' }
-   *   customHref: (category, args, router) => {  if (category && category.name) === 'not-a-bug') "/a-feature"; }
+   *   customHref: (category, args, router) => {  if (category && category.name) === 'not-a-bug') "/a-feature"; },
+   *   before: "top",
+   *   forceActive(category, args, router) => router.currentURL === "/a/b/c/d";
    * })
    */
   addNavigationBarItem(item) {
@@ -763,6 +765,14 @@ class PluginApi {
         };
       }
 
+      const forceActive = item.forceActive;
+      if (forceActive) {
+        const router = this.container.lookup("service:router");
+        item.forceActive = function(category, args) {
+          return forceActive(category, args, router);
+        };
+      }
+
       addNavItem(item);
     }
   }

app/assets/javascripts/discourse/models/nav-item.js.es6

@@ -193,12 +193,42 @@ NavItem.reopenClass({
       return item.customFilter.call(this, category, args);
     });
 
+    let forceActive = false;
+
     extraItems.forEach(item => {
+      const before = item.before;
+      if (before) {
+        let i = 0;
+        for (i = 0; i < items.length; i++) {
+          if (items[i].name === before) {
+            break;
+          }
+        }
+        items.splice(i, 0, item);
+      } else {
+        items.push(item);
+      }
+
       if (!item.customHref) return;
+
       item.set("href", item.customHref.call(this, category, args));
+
+      if (item.forceActive && item.forceActive.call(this, category, args)) {
+        item.active = true;
+        forceActive = true;
+      } else {
+        item.active = undefined;
+      }
     });
 
-    return items.concat(extraItems);
+    if (forceActive) {
+      items.forEach(i => {
+        if (i.active === undefined) {
+          i.active = false;
+        }
+      });
+    }
+    return items;
   }
 });