FIX: `UserNotificationsHelper#logo_url' to work with S3 based uploads.

https://meta.discourse.org/t/digest-logo-not-working/103255

app/helpers/user_notifications_helper.rb

@@ -1,4 +1,5 @@
 module UserNotificationsHelper
+  include GlobalPath
 
   def indent(text, by = 2)
     spacer = " " * by
@@ -22,11 +23,9 @@ module UserNotificationsHelper
     logo_url = SiteSetting.site_logo_url if logo_url.blank? || logo_url =~ /\.svg$/i
     return nil if logo_url.blank? || logo_url =~ /\.svg$/i
 
-    if logo_url !~ /http(s)?\:\/\//
-      logo_url = "#{Discourse.base_url}#{logo_url}"
-    end
-
-    logo_url
+    uri = URI.parse(UrlHelper.absolute(upload_cdn_path(logo_url)))
+    uri.scheme = SiteSetting.scheme if uri.scheme.blank?
+    uri.to_s
   end
 
   def html_site_link(color)

spec/helpers/user_notifications_helper_spec.rb

@@ -1,7 +1,7 @@
 require 'rails_helper'
 
 describe UserNotificationsHelper do
-  describe 'email_excerpt' do
+  describe '#email_excerpt' do
     let(:paragraphs) { [
       "<p>This is the first paragraph, but you should read more.</p>",
       "<p>And here is its friend, the second paragraph.</p>"
@@ -53,4 +53,72 @@ describe UserNotificationsHelper do
       expect(helper.email_excerpt(cooked)).to eq "<p>BEFORE</p><blockquote>\n  <p>This is a user quote</p>\n</blockquote><p>AFTER</p>"
     end
   end
+
+  describe '#logo_url' do
+    describe 'local store' do
+      let(:upload) { Fabricate(:upload, sha1: "somesha1") }
+
+      before do
+        SiteSetting.logo = upload
+      end
+
+      it 'should return the right URL' do
+        expect(helper.logo_url).to eq(
+          "http://test.localhost/uploads/default/original/1X/somesha1.png"
+        )
+      end
+
+      describe 'when cdn path is configured' do
+        before do
+          GlobalSetting.expects(:cdn_url)
+            .returns('https://some.localcdn.com')
+            .at_least_once
+        end
+
+        it 'should return the right URL' do
+          expect(helper.logo_url).to eq(
+            "https://some.localcdn.com/uploads/default/original/1X/somesha1.png"
+          )
+        end
+      end
+
+      describe 'when logo is an SVG' do
+        let(:upload) { Fabricate(:upload, extension: "svg") }
+
+        it 'should return nil' do
+          expect(helper.logo_url).to eq(nil)
+        end
+      end
+    end
+
+    describe 's3 store' do
+      let(:upload) { Fabricate(:upload_s3, sha1: "somesha1") }
+
+      before do
+        SiteSetting.enable_s3_uploads = true
+        SiteSetting.s3_upload_bucket = "s3-upload-bucket"
+        SiteSetting.s3_access_key_id = "some key"
+        SiteSetting.s3_secret_access_key = "some secret key"
+        SiteSetting.logo = upload
+      end
+
+      it 'should return the right URL' do
+        expect(helper.logo_url).to eq(
+          "http://s3-upload-bucket.s3.dualstack.us-east-1.amazonaws.com/original/1X/somesha1.png"
+        )
+      end
+
+      describe 'when cdn path is configured' do
+        before do
+          SiteSetting.s3_cdn_url = 'https://some.cdn.com'
+        end
+
+        it 'should return the right url' do
+          expect(helper.logo_url).to eq(
+            "https://some.cdn.com/original/1X/somesha1.png"
+          )
+        end
+      end
+    end
+  end
 end