Use the service_link at the start of the path to the favicon images if required

Author: johnsgp

CHANGELOG.md

@@ -1,3 +1,10 @@
+## Unreleased
+
+- [Fix: Use the service link as the start of the path to the favicon images if required](https://github.com/alphagov/tech-docs-gem/pull/399)
+
+To use the service_link at the start of the path to the favicon images, you need to
+- set `use_service_link_for_favicon: true`
+
 ## 4.3.1
 
 - Revert [Fix: Use the service link as the start of the path to the favicon images](https://github.com/alphagov/tech-docs-gem/pull/391)

lib/source/layouts/core.erb

@@ -11,11 +11,24 @@
 
     <link rel="canonical" href="<%= meta_tags.canonical_url %>">
     <% if config[:tech_docs][:show_govuk_logo] %>
-      <link rel="icon" sizes="48x48" href="/assets/govuk/assets/images/favicon.ico">
-      <link rel="icon" sizes="any" href="/assets/govuk/assets/images/favicon.svg" type="image/svg+xml">
-      <link rel="mask-icon" href="/assets/govuk/assets/images/govuk-icon-mask.svg" color="#0b0c0c">
-      <link rel="apple-touch-icon" href="/assets/govuk/assets/images/govuk-icon-180.png">
-      <link rel="manifest" href="/assets/govuk/assets/manifest.json">
+      <%
+        path_prefix =
+          if !development? && config[:tech_docs][:use_service_link_for_favicon]
+            service_link = config[:tech_docs][:service_link] || '/'
+            # ensure service_link ends with a trailing '/'
+            if service_link[-1, 1] != '/'
+              service_link += '/'
+            end
+            service_link
+          else
+            '/'
+          end
+      %>
+      <link rel="icon" sizes="48x48" href="<%= path_prefix %>assets/govuk/assets/images/favicon.ico">
+      <link rel="icon" sizes="any" href="<%= path_prefix %>assets/govuk/assets/images/favicon.svg" type="image/svg+xml">
+      <link rel="mask-icon" href="<%= path_prefix %>assets/govuk/assets/images/govuk-icon-mask.svg" color="#0b0c0c">
+      <link rel="apple-touch-icon" href="<%= path_prefix %>assets/govuk/assets/images/govuk-icon-180.png">
+      <link rel="manifest" href="<%= path_prefix %>assets/govuk/assets/manifest.json">
     <% else %>
       <link rel="icon" sizes="48x48" href="/images/favicon.ico">
       <link rel="icon" sizes="any" href="/images/favicon.svg" type="image/svg+xml">