Only use shallow nested scope when depth is > 1

By tracking the depth of resource nesting we can push the need for nested
shallow scoping to only those routes that are nested more than one deep.
This allows us to keep the fix for #12498 and fix the regression in #14224.

Fixes #14224.

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -1323,8 +1323,10 @@ def member
           end
 
           with_scope_level(:member) do
-            scope(parent_resource.member_scope) do
-              yield
+            if shallow?
+              shallow_scope(parent_resource.member_scope) { yield }
+            else
+              scope(parent_resource.member_scope) { yield }
             end
           end
         end
@@ -1347,16 +1349,8 @@ def nested
           end
 
           with_scope_level(:nested) do
-            if shallow?
-              with_exclusive_scope do
-                if @scope[:shallow_path].blank?
-                  scope(parent_resource.nested_scope, nested_options) { yield }
-                else
-                  scope(@scope[:shallow_path], :as => @scope[:shallow_prefix]) do
-                    scope(parent_resource.nested_scope, nested_options) { yield }
-                  end
-                end
-              end
+            if shallow? && nesting_depth > 1
+              shallow_scope(parent_resource.nested_scope, nested_options) { yield }
             else
               scope(parent_resource.nested_scope, nested_options) { yield }
             end
@@ -1567,11 +1561,13 @@ def with_scope_level(kind)
 
           def resource_scope(kind, resource) #:nodoc:
             old_resource, @scope[:scope_level_resource] = @scope[:scope_level_resource], resource
+            @nesting.push(resource)
 
             with_scope_level(kind) do
               scope(parent_resource.resource_scope) { yield }
             end
           ensure
+            @nesting.pop
             @scope[:scope_level_resource] = old_resource
           end
 
@@ -1584,6 +1580,10 @@ def nested_options #:nodoc:
             options
           end
 
+          def nesting_depth #:nodoc:
+            @nesting.size
+          end
+
           def param_constraint? #:nodoc:
             @scope[:constraints] && @scope[:constraints][parent_resource.param].is_a?(Regexp)
           end
@@ -1596,18 +1596,20 @@ def canonical_action?(action, flag) #:nodoc:
             flag && resource_method_scope? && CANONICAL_ACTIONS.include?(action.to_s)
           end
 
-          def shallow_scoping? #:nodoc:
-            shallow? && @scope[:scope_level] == :member
+          def shallow_scope(path, options = {}) #:nodoc:
+            old_name_prefix, old_path = @scope[:as], @scope[:path]
+            @scope[:as], @scope[:path] = @scope[:shallow_prefix], @scope[:shallow_path]
+
+            scope(path, options) { yield }
+          ensure
+            @scope[:as], @scope[:path] = old_name_prefix, old_path
           end
 
           def path_for_action(action, path) #:nodoc:
-            prefix = shallow_scoping? ?
-              "#{@scope[:shallow_path]}/#{parent_resource.shallow_scope}" : @scope[:path]
-
             if canonical_action?(action, path.blank?)
-              prefix.to_s
+              @scope[:path].to_s
             else
-              "#{prefix}/#{action_path(action, path)}"
+              "#{@scope[:path]}/#{action_path(action, path)}"
             end
           end
 
@@ -1645,7 +1647,7 @@ def name_for_action(as, action) #:nodoc:
             when :new
               [prefix, :new, name_prefix, member_name]
             when :member
-              [prefix, shallow_scoping? ? @scope[:shallow_prefix] : name_prefix, member_name]
+              [prefix, name_prefix, member_name]
             when :root
               [name_prefix, collection_name, prefix]
             else
@@ -1786,6 +1788,7 @@ def initialize(set) #:nodoc:
         @set = set
         @scope = { :path_names => @set.resources_path_names }
         @concerns = {}
+        @nesting = []
       end
 
       include Base

actionpack/test/dispatch/routing_test.rb

@@ -3033,6 +3033,66 @@ def test_shallow_path_inside_namespace_is_not_added_twice
     assert_equal '/admin/posts/1/comments', admin_post_comments_path('1')
   end
 
+  def test_shallow_path_and_prefix_are_not_added_to_non_shallow_routes
+    draw do
+      scope shallow_path: 'projects', shallow_prefix: 'project' do
+        resources :projects do
+          resources :files, controller: 'project_files', shallow: true
+        end
+      end
+    end
+
+    get '/projects'
+    assert_equal 'projects#index', @response.body
+    assert_equal '/projects', projects_path
+
+    get '/projects/new'
+    assert_equal 'projects#new', @response.body
+    assert_equal '/projects/new', new_project_path
+
+    post '/projects'
+    assert_equal 'projects#create', @response.body
+
+    get '/projects/1'
+    assert_equal 'projects#show', @response.body
+    assert_equal '/projects/1', project_path('1')
+
+    get '/projects/1/edit'
+    assert_equal 'projects#edit', @response.body
+    assert_equal '/projects/1/edit', edit_project_path('1')
+
+    patch '/projects/1'
+    assert_equal 'projects#update', @response.body
+
+    delete '/projects/1'
+    assert_equal 'projects#destroy', @response.body
+
+    get '/projects/1/files'
+    assert_equal 'project_files#index', @response.body
+    assert_equal '/projects/1/files', project_files_path('1')
+
+    get '/projects/1/files/new'
+    assert_equal 'project_files#new', @response.body
+    assert_equal '/projects/1/files/new', new_project_file_path('1')
+
+    post '/projects/1/files'
+    assert_equal 'project_files#create', @response.body
+
+    get '/projects/files/2'
+    assert_equal 'project_files#show', @response.body
+    assert_equal '/projects/files/2', project_file_path('2')
+
+    get '/projects/files/2/edit'
+    assert_equal 'project_files#edit', @response.body
+    assert_equal '/projects/files/2/edit', edit_project_file_path('2')
+
+    patch '/projects/files/2'
+    assert_equal 'project_files#update', @response.body
+
+    delete '/projects/files/2'
+    assert_equal 'project_files#destroy', @response.body
+  end
+
 private
 
   def draw(&block)