FIX: Render links with subfolders properly in Discobot

Currently, some links aren’t properly built in Discobot when Discourse
is hosted in a subfolder. This is because we’re providing
`Discourse.base_url` to the Rails helpers which contains the base URL
*with* the prefix. But Rails helpers already handle this prefix so the
resulting link gets the prefix twice.

The fix is quite simple: use `Discourse.base_url_no_prefix` instead of
`Discourse.base_url`.

plugins/discourse-narrative-bot/lib/discourse_narrative_bot/new_user_narrative.rb

@@ -638,7 +638,10 @@ module DiscourseNarrativeBot
     end
 
     def url_helpers(url, opts = {})
-      Rails.application.routes.url_helpers.public_send(url, opts.merge(host: Discourse.base_url))
+      Rails.application.routes.url_helpers.public_send(
+        url,
+        opts.merge(host: Discourse.base_url_no_prefix),
+      )
     end
   end
 end

plugins/discourse-narrative-bot/spec/discourse_narrative_bot/new_user_narrative_spec.rb

@@ -286,22 +286,27 @@ RSpec.describe DiscourseNarrativeBot::NewUserNarrative do
         )
       end
 
-      it "should create the right reply when the bookmark is created" do
-        post.update!(user: discobot_user)
-        narrative.expects(:enqueue_timeout_job).with(user)
-
-        narrative.input(:bookmark, user, post: post)
-        new_post = Post.last
-        profile_page_url = "#{Discourse.base_url}/u/#{user.username}"
-
-        expected_raw = <<~RAW
+      context "when the bookmark is created" do
+        let(:profile_page_url) { "#{Discourse.base_url_no_prefix}/prefix/u/#{user.username}" }
+        let(:new_post) { Post.last }
+        let(:user_state) { narrative.get_data(user)[:state].to_sym }
+        let(:expected_raw) { <<~RAW }
           #{I18n.t("discourse_narrative_bot.new_user_narrative.bookmark.reply", bookmark_url: "#{profile_page_url}/activity/bookmarks", base_uri: "")}
 
           #{I18n.t("discourse_narrative_bot.new_user_narrative.onebox.instructions", base_uri: "")}
         RAW
 
-        expect(new_post.raw).to eq(expected_raw.chomp)
-        expect(narrative.get_data(user)[:state].to_sym).to eq(:tutorial_onebox)
+        before do
+          set_subfolder("/prefix")
+          post.update!(user: discobot_user)
+          narrative.stubs(:enqueue_timeout_job).with(user)
+        end
+
+        it "creates the right reply" do
+          narrative.input(:bookmark, user, post: post)
+          expect(new_post.raw).to eq(expected_raw.chomp)
+          expect(user_state).to eq(:tutorial_onebox)
+        end
       end
 
       it "should skip tutorials in SiteSetting.discourse_narrative_bot_skip_tutorials" do

spec/support/helpers.rb

@@ -153,6 +153,7 @@ module Helpers
     global_setting :relative_url_root, f
     old_root = ActionController::Base.config.relative_url_root
     ActionController::Base.config.relative_url_root = f
+    Rails.application.routes.stubs(:relative_url_root).returns(f)
 
     before_next_spec { ActionController::Base.config.relative_url_root = old_root }
   end