ci: fix $CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX for non-lowercase groups

Docker does not allow uppercase characters in the image path, but GitLab
allows them in the group name, which is used in the dependency proxy's
image prefix.

The proxy already works with lowercased group names, the only thing
needed is to make sure we pass the correct prefix to the CI and to the
web page user.

app/models/project.rb

@@ -2041,7 +2041,9 @@ class Project < ApplicationRecord
       variables.append(key: 'CI_DEPENDENCY_PROXY_SERVER', value: Gitlab.host_with_port)
       variables.append(
         key: 'CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX',
-        value: "#{Gitlab.host_with_port}/#{namespace.root_ancestor.path}#{DependencyProxy::URL_SUFFIX}"
+        # The namespace path can include uppercase letters, which
+        # Docker doesn't allow. The proxy expects it to be downcased.
+        value: "#{Gitlab.host_with_port}/#{namespace.root_ancestor.path.downcase}#{DependencyProxy::URL_SUFFIX}"
       )
     end
   end

app/views/groups/dependency_proxies/_url.html.haml

-- proxy_url = "#{group_url(@group)}#{DependencyProxy::URL_SUFFIX}"
+-# The namespace path can include uppercase letters, which
+-# Docker doesn't allow. The proxy expects it to be downcased.
+- proxy_url = "#{group_url(@group).downcase}#{DependencyProxy::URL_SUFFIX}"
 
 %h5.prepend-top-20= _('Dependency proxy URL')
 

changelogs/unreleased/fix-ci-dependency-proxy-group-name.yml

+---
+title: Fix the value of `$CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX` when used in group with a name containing uppercase letters
+merge_request: 54559
+author: Eric Engestrom @1ace
+type: fixed

doc/user/packages/dependency_proxy/index.md

@@ -89,6 +89,7 @@ You can authenticate using:
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/280582) in GitLab 13.7.
 > - Automatic runner authentication [added](https://gitlab.com/gitlab-org/gitlab-runner/-/issues/27302) in GitLab 13.9.
+> - The prefix for group names containing uppercase letters was [fixed](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/54559) in GitLab 13.10.
 
 Runners log in to the Dependency Proxy automatically. To pull through
 the Dependency Proxy, use the `CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX`

spec/models/ci/build_spec.rb

@@ -2467,7 +2467,7 @@ RSpec.describe Ci::Build do
           { key: 'CI_PAGES_URL', value: project.pages_url, public: true, masked: false },
           { key: 'CI_DEPENDENCY_PROXY_SERVER', value: Gitlab.host_with_port, public: true, masked: false },
           { key: 'CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX',
-            value: "#{Gitlab.host_with_port}/#{project.namespace.root_ancestor.path}#{DependencyProxy::URL_SUFFIX}",
+            value: "#{Gitlab.host_with_port}/#{project.namespace.root_ancestor.path.downcase}#{DependencyProxy::URL_SUFFIX}",
             public: true,
             masked: false },
           { key: 'CI_API_V4_URL', value: 'http://localhost/api/v4', public: true, masked: false },

spec/models/project_spec.rb

@@ -4488,6 +4488,34 @@ RSpec.describe Project, factory_default: :keep do
     end
   end
 
+  describe '#dependency_proxy_variables' do
+    let_it_be(:namespace) { create(:namespace, path: 'NameWithUPPERcaseLetters') }
+    let_it_be(:project) { create(:project, :repository, namespace: namespace) }
+
+    subject { project.dependency_proxy_variables.to_runner_variables }
+
+    context 'when dependency_proxy is enabled' do
+      before do
+        stub_config(dependency_proxy: { enabled: true })
+      end
+
+      it 'contains the downcased name' do
+        expect(subject).to include({ key: 'CI_DEPENDENCY_PROXY_GROUP_IMAGE_PREFIX',
+                                     value: "#{Gitlab.host_with_port}/namewithuppercaseletters#{DependencyProxy::URL_SUFFIX}",
+                                     public: true,
+                                     masked: false })
+      end
+    end
+
+    context 'when dependency_proxy is disabled' do
+      before do
+        stub_config(dependency_proxy: { enabled: false })
+      end
+
+      it { expect(subject).to be_empty }
+    end
+  end
+
   describe '#auto_devops_enabled?' do
     before do
       Feature.enable_percentage_of_actors(:force_autodevops_on_by_default, 0)