Don't hard-code Administrate's URL namespace

Problem:

Administrate requires that its dashboards be mounted at `/admin`.

In applications with an `Admin` model,
Administrate will cause an error
because it will try to define `Admin` as a module
when it's already been defined as a class.

The hard-coded namespace limits users' freedom
in defining their own URL schema,
and prevents users from mounting
multiple Administrate dashboards at once.

Solution:

Dynamically evaluate Administrate's namespace from the request's URL.
This dynamically calculated value is used for all links and redirects
in Administrate dashboards.

The namespace is now only set by generators.
If a user wants to change their namespace
away from the default of `admin`,
they must run the generators and manually change `admin`
to the namespace of their choice.

Next Steps:

Change generators to accept
(or read from some configuration file)
an optional namespace argument
instead of always using the `admin` namespace.

app/controllers/administrate/application_controller.rb

@@ -37,7 +37,7 @@ def create
 
       if resource.save
         redirect_to(
-          [Administrate::NAMESPACE, resource],
+          [namespace, resource],
           notice: translate_with_resource("create.success"),
         )
       else
@@ -50,7 +50,7 @@ def create
     def update
       if requested_resource.update(resource_params)
         redirect_to(
-          [Administrate::NAMESPACE, requested_resource],
+          [namespace, requested_resource],
           notice: translate_with_resource("update.success"),
         )
       else
@@ -105,7 +105,8 @@ def permitted_attributes
       dashboard.permitted_attributes
     end
 
-    delegate :resource_class, :resource_name, to: :resource_resolver
+    delegate :resource_class, :resource_name, :namespace, to: :resource_resolver
+    helper_method :namespace
 
     def resource_resolver
       @_resource_resolver ||=

app/views/administrate/application/_collection.html.erb

@@ -47,7 +47,7 @@ to display a collection of resources in an HTML table.
       <tr class="table__row"
           role="link"
           tabindex="0"
-          data-url="<%= polymorphic_path([Administrate::NAMESPACE, resource]) -%>"
+          data-url="<%= polymorphic_path([namespace, resource]) -%>"
           >
         <% collection_presenter.attributes_for(resource).each do |attribute| %>
           <td class="cell-data cell-data--<%= attribute.html_class %>">
@@ -57,13 +57,13 @@ to display a collection of resources in an HTML table.
 
         <td><%= link_to(
           t("administrate.actions.edit"),
-          [:edit, Administrate::NAMESPACE, resource],
+          [:edit, namespace, resource],
           class: "action-edit",
         ) %></td>
 
         <td><%= link_to(
           t("administrate.actions.destroy"),
-          [Administrate::NAMESPACE, resource],
+          [namespace, resource],
           class: "table__action--destroy",
           method: :delete,
           data: { confirm: t("administrate.actions.confirm") }

app/views/administrate/application/_form.html.erb

@@ -14,7 +14,7 @@ and renders all form fields for a resource's editable attributes.
 [1]: http://www.rubydoc.info/gems/administrate/Administrate/Page/Form
 %>
 
-<%= form_for([Administrate::NAMESPACE, page.resource], html: { class: "form" }) do |f| %>
+<%= form_for([namespace, page.resource], html: { class: "form" }) do |f| %>
   <% if page.resource.errors.any? %>
     <div id="error_explanation">
       <h2>

app/views/administrate/application/_sidebar.html.erb

@@ -12,7 +12,7 @@ as defined by the DashboardManifest.
     <li>
       <%= link_to(
         display_resource_name(resource),
-        [Administrate::NAMESPACE, resource],
+        [namespace, resource],
         class: "sidebar__link sidebar__link--#{nav_link_state(resource)}"
       ) %>
     </li>

app/views/administrate/application/edit.html.erb

@@ -22,7 +22,7 @@ It displays a header, and renders the `_form` partial to do the heavy lifting.
   <div class="header-actions">
     <%= link_to(
       "Show #{page.page_title}",
-      [Administrate::NAMESPACE, page.resource],
+      [namespace, page.resource],
       class: "button",
     ) %>
   </div>

app/views/administrate/application/index.html.erb

@@ -48,7 +48,7 @@ It renders the `_table` partial to display details about the resources.
   <div class="header-actions">
     <%= link_to(
       "New #{page.resource_name.titleize.downcase}",
-      [:new, Administrate::NAMESPACE, page.resource_name],
+      [:new, namespace, page.resource_name],
       class: "button",
     ) %>
   </div>

app/views/administrate/application/show.html.erb

@@ -23,7 +23,7 @@ as well as a link to its edit page.
   <div class="header-actions">
     <%= link_to(
       "Edit",
-      [:edit, Administrate::NAMESPACE, page.resource],
+      [:edit, namespace, page.resource],
       class: "button",
     ) %>
   </div>

app/views/fields/belongs_to/_index.html.erb

@@ -18,6 +18,6 @@ By default, the relationship is rendered as a link to the associated object.
 <% if field.data %>
   <%= link_to(
     field.display_associated_resource,
-    [Administrate::NAMESPACE, field.data],
+    [namespace, field.data],
   ) %>
 <% end %>

app/views/fields/belongs_to/_show.html.erb

@@ -18,6 +18,6 @@ By default, the relationship is rendered as a link to the associated object.
 <% if field.data %>
   <%= link_to(
     field.display_associated_resource,
-    [Administrate::NAMESPACE, field.data],
+    [namespace, field.data],
   ) %>
 <% end %>

app/views/fields/has_one/_index.html.erb

@@ -18,6 +18,6 @@ By default, the relationship is rendered as a link to the associated object.
 <% if field.data %>
   <%= link_to(
     field.display_associated_resource,
-    [Administrate::NAMESPACE, field.data],
+    [namespace, field.data],
   ) %>
 <% end %>

app/views/fields/has_one/_show.html.erb

@@ -18,6 +18,6 @@ By default, the relationship is rendered as a link to the associated object.
 <% if field.data %>
   <%= link_to(
     field.display_associated_resource,
-    [Administrate::NAMESPACE, field.data],
+    [namespace, field.data],
   ) %>
 <% end %>

app/views/fields/polymorphic/_index.html.erb

@@ -19,6 +19,6 @@ By default, the relationship is rendered as a link to the associated object.
 <% if field.data %>
   <%= link_to(
     field.display_associated_resource,
-    [Administrate::NAMESPACE, field.data]
+    [namespace, field.data]
   ) %>
 <% end %>

app/views/fields/polymorphic/_show.html.erb

@@ -19,6 +19,6 @@ By default, the relationship is rendered as a link to the associated object.
 <% if field.data %>
   <%= link_to(
     field.display_associated_resource,
-    [Administrate::NAMESPACE, field.data],
+    [namespace, field.data],
   ) %>
 <% end %>

lib/administrate/engine.rb

@@ -9,7 +9,6 @@
 require "selectize-rails"
 require "sprockets/railtie"
 
-require "administrate/namespace"
 require "administrate/page/form"
 require "administrate/page/show"
 require "administrate/page/collection"

lib/administrate/resource_resolver.rb

@@ -1,5 +1,3 @@
-require "administrate/namespace"
-
 module Administrate
   class ResourceResolver
     def initialize(controller_path)
@@ -10,6 +8,10 @@ def dashboard_class
       Object.const_get(resource_class_name + "Dashboard")
     end
 
+    def namespace
+      controller_path.split("/").first
+    end
+
     def resource_class
       Object.const_get(resource_class_name)
     end
@@ -33,7 +35,7 @@ def model_path_parts
     end
 
     def controller_path_parts
-      controller_path.singularize.split("/") - [Administrate::NAMESPACE.to_s]
+      controller_path.singularize.split("/")[1..-1]
     end
 
     attr_reader :controller_path

spec/administrate/views/fields/has_one/_index_spec.rb

@@ -1,7 +1,7 @@
 require "rails_helper"
 
 describe "fields/has_one/_index", type: :view do
-  context "without an associated records" do
+  context "without an associated record" do
     it "displays nothing" do
       has_one = double(data: nil)
 
@@ -26,7 +26,7 @@
 
       render(
         partial: "fields/has_one/index.html.erb",
-        locals: { field: has_one },
+        locals: { field: has_one, namespace: "admin" },
       )
 
       expected = "<a href=\"#{product_path}\">#{product.name}</a>"

spec/administrate/views/fields/has_one/_show_spec.rb

@@ -2,7 +2,7 @@
 require "administrate/fields/has_one"
 
 describe "fields/has_one/_show", type: :view do
-  context "without an associated records" do
+  context "without an associated record" do
     it "displays nothing" do
       has_one = instance_double(
         "Administrate::Field::HasOne",
@@ -31,7 +31,7 @@
 
       render(
         partial: "fields/has_one/show.html.erb",
-        locals: { field: has_one },
+        locals: { field: has_one, namespace: "admin" },
       )
 
       expected = "<a href=\"#{product_path}\">#{product.name}</a>"

spec/administrate/views/fields/polymorphic/_index_spec.rb

@@ -26,7 +26,7 @@
 
       render(
         partial: "fields/polymorphic/index.html.erb",
-        locals: { field: polymorphic },
+        locals: { field: polymorphic, namespace: "admin" },
       )
 
       expected = "<a href=\"#{product_path}\">#{product.name}</a>"

spec/administrate/views/fields/polymorphic/_show_spec.rb

@@ -31,7 +31,7 @@
 
       render(
         partial: "fields/polymorphic/show.html.erb",
-        locals: { field: polymorphic },
+        locals: { field: polymorphic, namespace: "admin" },
       )
 
       expected = "<a href=\"#{product_path}\">#{product.name}</a>"

spec/lib/administrate/resource_resolver_spec.rb

@@ -1,50 +1,59 @@
 require "spec_helper"
+require "active_support/core_ext/string/inflections"
 require "support/constant_helpers"
 require "administrate/resource_resolver"
 
 describe Administrate::ResourceResolver do
-  describe "#resource_class" do
+  describe "#dashboard_class" do
     it "handles global-namepsace models" do
       begin
-        class User; end
+        class UserDashboard; end
         resolver = Administrate::ResourceResolver.new("admin/users")
 
-        expect(resolver.resource_class).to eq(User)
+        expect(resolver.dashboard_class).to eq(UserDashboard)
       ensure
-        remove_constants :User
+        remove_constants :UserDashboard
       end
     end
 
     it "handles namespaced models" do
       begin
-        module Blog; class Post; end; end
+        module Blog; class PostDashboard; end; end
         resolver = Administrate::ResourceResolver.new("admin/blog/posts")
 
-        expect(resolver.resource_class).to eq(Blog::Post)
+        expect(resolver.dashboard_class).to eq(Blog::PostDashboard)
       ensure
         remove_constants :Blog
       end
     end
   end
 
-  describe "#dashboard_class" do
+  describe "#namespace" do
+    it "returns the top-level namespace" do
+      resolver = Administrate::ResourceResolver.new("foobar/user")
+
+      expect(resolver.namespace).to eq("foobar")
+    end
+  end
+
+  describe "#resource_class" do
     it "handles global-namepsace models" do
       begin
-        class UserDashboard; end
+        class User; end
         resolver = Administrate::ResourceResolver.new("admin/users")
 
-        expect(resolver.dashboard_class).to eq(UserDashboard)
+        expect(resolver.resource_class).to eq(User)
       ensure
-        remove_constants :UserDashboard
+        remove_constants :User
       end
     end
 
     it "handles namespaced models" do
       begin
-        module Blog; class PostDashboard; end; end
+        module Blog; class Post; end; end
         resolver = Administrate::ResourceResolver.new("admin/blog/posts")
 
-        expect(resolver.dashboard_class).to eq(Blog::PostDashboard)
+        expect(resolver.resource_class).to eq(Blog::Post)
       ensure
         remove_constants :Blog
       end

spec/support/table.rb

@@ -17,7 +17,7 @@ def clickable_table_elements
 
   def url_for(model)
     "/" + [
-      Administrate::NAMESPACE,
+      :admin,
       model.class.to_s.underscore.pluralize,
       model.to_param,
     ].join("/")