DEV: Prevent setting filterMode where it can be already be computed

The plan is to switch over all cases where filterMode is set, but, to
prevent breaking plugins and themes, the category and noSubcategories
need to be inferred from any given filterMode before that can happen.

app/assets/javascripts/discourse/routes/build-category-route.js.es6

@@ -66,14 +66,12 @@ export default (filterArg, params) => {
 
     _setupNavigation(category) {
       const noSubcategories = params && !!params.no_subcategories,
-        filterMode = `c/${Category.slugFor(category)}${
-          noSubcategories ? "/none" : ""
-        }/l/${this.filter(category)}`;
+        filterType = this.filter(category).split("/")[0];
 
       this.controllerFor("navigation/category").setProperties({
         category,
-        filterMode: filterMode,
-        noSubcategories: params && params.no_subcategories
+        filterType,
+        noSubcategories
       });
     },
 

app/assets/javascripts/discourse/routes/build-topic-route.js.es6

@@ -80,7 +80,10 @@ export default function(filter, extras) {
       queryParams,
 
       beforeModel() {
-        this.controllerFor("navigation/default").set("filterMode", filter);
+        this.controllerFor("navigation/default").set(
+          "filterType",
+          filter.split("/")[0]
+        );
       },
 
       model(data, transition) {

app/assets/javascripts/discourse/routes/tags-show.js.es6

@@ -24,8 +24,6 @@ export default DiscourseRoute.extend(FilterModeMixin, {
     const tag = this.store.createRecord("tag", {
       id: Handlebars.Utils.escapeExpression(params.tag_id)
     });
-    let f = "";
-
     if (params.additional_tags) {
       this.set(
         "additionalTags",
@@ -39,15 +37,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
       this.set("additionalTags", null);
     }
 
-    if (params.category) {
-      f = "c/";
-      if (params.parent_category) {
-        f += `${params.parent_category}/`;
-      }
-      f += `${params.category}/l/`;
-    }
-    f += this.navMode;
-    this.set("filterMode", f);
+    this.set("filterType", this.navMode.split("/")[0]);
 
     if (params.category) {
       this.set("categorySlug", params.category);
@@ -161,7 +151,7 @@ export default DiscourseRoute.extend(FilterModeMixin, {
       tag: model,
       additionalTags: this.additionalTags,
       category: this.category,
-      filterMode: this.filterMode,
+      filterType: this.filterType,
       navMode: this.navMode,
       tagNotification: this.tagNotification,
       noSubcategories: this.noSubcategories

app/assets/javascripts/discourse/templates/navigation/categories.hbs

@@ -1,6 +1,6 @@
 {{#d-section bodyClass="navigation-categories" class="navigation-container"}}
   {{d-navigation
-    filterMode="categories"
+    filterType="categories"
     showCategoryAdmin=showCategoryAdmin
     createCategory=(route-action "createCategory")
     reorderCategories=(route-action "reorderCategories")