Add support for numeric-based URIs for local accounts

app/controllers/accounts_controller.rb

@@ -71,6 +71,10 @@ class AccountsController < ApplicationController
     params[:username]
   end
 
+  def account_id_param
+    params[:id]
+  end
+
   def skip_temporary_suspension_response?
     request.format == :json
   end

app/controllers/concerns/account_owned_concern.rb

@@ -18,7 +18,11 @@ module AccountOwnedConcern
   end
 
   def set_account
-    @account = Account.find_local!(username_param)
+    @account = username_param.present? ? Account.find_local!(username_param) : Account.local.find(account_id_param)
+  end
+
+  def account_id_param
+    params[:numeric_account_id]
   end
 
   def username_param

config/routes.rb

@@ -117,6 +117,29 @@ Rails.application.routes.draw do
     end
   end
 
+  resources :accounts, path: 'u', only: [:show], param: :id, as: :numeric_account do
+    resources :statuses, only: [:show] do
+      member do
+        get :activity
+        get :embed
+      end
+
+      resources :replies, only: [:index], module: :activitypub
+      resources :likes, only: [:index], module: :activitypub
+      resources :shares, only: [:index], module: :activitypub
+    end
+
+    resources :followers, only: [:index], controller: :follower_accounts
+    resources :following, only: [:index], controller: :following_accounts
+
+    scope module: :activitypub do
+      resource :outbox, only: [:show]
+      resource :inbox, only: [:create]
+      resources :collections, only: [:show]
+      resource :followers_synchronization, only: [:show]
+    end
+  end
+
   resource :inbox, only: [:create], module: :activitypub
 
   constraints(encoded_path: /%40.*/) do

spec/requests/accounts_spec.rb

@@ -5,6 +5,14 @@ require 'rails_helper'
 RSpec.describe 'Accounts show response' do
   let(:account) { Fabricate(:account) }
 
+  context 'with numeric-based identifiers' do
+    it 'returns http success' do
+      get "/u/#{account.id}"
+
+      expect(response).to have_http_status(200)
+    end
+  end
+
   context 'with an unapproved account' do
     before { account.user.update(approved: false) }