Add GraphQL endpoint for fetching a cluster agent by name

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/40779

app/models/clusters/agent.rb

@@ -8,6 +8,8 @@ module Clusters
 
     has_many :agent_tokens, class_name: 'Clusters::AgentToken'
 
+    scope :with_name, -> (name) { where(name: name) }
+
     validates :name,
       presence: true,
       length: { maximum: 63 },

doc/api/graphql/reference/gitlab_schema.graphql

@@ -11671,6 +11671,16 @@ type Project {
     last: Int
   ): BoardConnection
 
+  """
+  Find a single cluster agent by name
+  """
+  clusterAgent(
+    """
+    Name of the cluster agent
+    """
+    name: String!
+  ): ClusterAgent
+
   """
   Cluster agents associated with the project
   """

doc/api/graphql/reference/gitlab_schema.json

@@ -34762,6 +34762,33 @@
               "isDeprecated": false,
               "deprecationReason": null
             },
+            {
+              "name": "clusterAgent",
+              "description": "Find a single cluster agent by name",
+              "args": [
+                {
+                  "name": "name",
+                  "description": "Name of the cluster agent",
+                  "type": {
+                    "kind": "NON_NULL",
+                    "name": null,
+                    "ofType": {
+                      "kind": "SCALAR",
+                      "name": "String",
+                      "ofType": null
+                    }
+                  },
+                  "defaultValue": null
+                }
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "ClusterAgent",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
             {
               "name": "clusterAgents",
               "description": "Cluster agents associated with the project",

doc/api/graphql/reference/index.md

@@ -1747,6 +1747,7 @@ Autogenerated return type of PipelineRetry
 | `autocloseReferencedIssues` | Boolean | Indicates if issues referenced by merge requests and commits within the default branch are closed automatically |
 | `avatarUrl` | String | URL to avatar image file of the project |
 | `board` | Board | A single board of the project |
+| `clusterAgent` | ClusterAgent | Find a single cluster agent by name |
 | `containerExpirationPolicy` | ContainerExpirationPolicy | The container expiration policy of the project |
 | `containerRegistryEnabled` | Boolean | Indicates if the project stores Docker container images in a container registry |
 | `createdAt` | Time | Timestamp of the project creation |

ee/app/finders/clusters/agents_finder.rb

@@ -11,12 +11,15 @@ module Clusters
     def execute
       return ::Clusters::Agent.none unless can_read_cluster_agents?
 
-      project.cluster_agents
+      agents = project.cluster_agents
+      agents = agents.with_name(params[:name]) if params[:name].present?
+
+      agents
     end
 
     private
 
-    attr_reader :project, :current_user
+    attr_reader :project, :current_user, :params
 
     def can_read_cluster_agents?
       project.feature_available?(:cluster_agents) && current_user.can?(:read_cluster, project)

ee/app/graphql/ee/types/project_type.rb

@@ -93,6 +93,12 @@ module EE
               description: 'DAST Site Profiles associated with the project',
               resolve: -> (obj, _args, _ctx) { obj.dast_site_profiles.with_dast_site }
 
+        field :cluster_agent,
+              ::Types::Clusters::AgentType,
+              null: true,
+              description: 'Find a single cluster agent by name',
+              resolver: ::Resolvers::Clusters::AgentResolver.single
+
         field :cluster_agents,
               ::Types::Clusters::AgentType.connection_type,
               null: true,

ee/app/graphql/resolvers/clusters/agent_resolver.rb

+# frozen_string_literal: true
+
+module Resolvers
+  module Clusters
+    class AgentResolver < AgentsResolver
+      argument :name, GraphQL::STRING_TYPE,
+               required: true,
+               description: 'Name of the cluster agent'
+    end
+  end
+end

ee/app/graphql/resolvers/clusters/agents_resolver.rb

@@ -9,7 +9,7 @@ module Resolvers
 
       def resolve(**args)
         ::Clusters::AgentsFinder
-          .new(project, context[:current_user])
+          .new(project, context[:current_user], params: args)
           .execute
       end
     end

ee/spec/finders/clusters/agents_finder_spec.rb

@@ -30,5 +30,23 @@ RSpec.describe Clusters::AgentsFinder do
 
       it { is_expected.to be_empty }
     end
+
+    context 'filtering by name' do
+      let(:params) { Hash(name: name_param) }
+
+      subject { described_class.new(project, user, params: params).execute }
+
+      context 'name does not match' do
+        let(:name_param) { 'other-name' }
+
+        it { is_expected.to be_empty }
+      end
+
+      context 'name does match' do
+        let(:name_param) { matching_agent.name }
+
+        it { is_expected.to contain_exactly(matching_agent) }
+      end
+    end
   end
 end

ee/spec/graphql/resolvers/clusters/agent_resolver_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Resolvers::Clusters::AgentResolver do
+  it { expect(described_class).to be < Resolvers::Clusters::AgentsResolver }
+
+  describe 'arguments' do
+    subject { described_class.arguments[argument] }
+
+    describe 'name' do
+      let(:argument) { 'name' }
+
+      it do
+        expect(subject).to be_present
+        expect(subject.type.to_s).to eq('String!')
+        expect(subject.description).to be_present
+      end
+    end
+  end
+end

ee/spec/graphql/resolvers/clusters/agents_resolver_spec.rb

@@ -13,12 +13,14 @@ RSpec.describe Resolvers::Clusters::AgentsResolver do
 
     let(:finder) { double(execute: :result) }
     let(:project) { create(:project) }
+    let(:args) { Hash(key: 'value') }
+    let(:ctx) { Hash(current_user: user) }
 
-    subject { resolve(described_class, obj: project, ctx: { current_user: user }) }
+    subject { resolve(described_class, obj: project, args: args, ctx: ctx) }
 
     it 'calls the agents finder' do
       expect(::Clusters::AgentsFinder).to receive(:new)
-        .with(project, user).and_return(finder)
+        .with(project, user, params: args).and_return(finder)
 
       expect(subject).to eq(:result)
     end

ee/spec/graphql/types/project_type_spec.rb

@@ -228,4 +228,44 @@ RSpec.describe GitlabSchema.types['Project'] do
       expect(agents.first['project']['id']).to eq(project.to_global_id.to_s)
     end
   end
+
+  describe 'cluster_agent' do
+    let_it_be(:cluster_agent) { create(:cluster_agent, project: project, name: 'agent-name') }
+    let_it_be(:query) do
+      %(
+        query {
+          project(fullPath: "#{project.full_path}") {
+            clusterAgent(name: "#{cluster_agent.name}") {
+              id
+              name
+              createdAt
+              updatedAt
+
+              project {
+                id
+              }
+            }
+          }
+        }
+      )
+    end
+
+    subject { GitlabSchema.execute(query, context: { current_user: user }).as_json }
+
+    before do
+      stub_licensed_features(cluster_agents: true)
+
+      project.add_maintainer(user)
+    end
+
+    it 'returns associated cluster agents' do
+      agent = subject.dig('data', 'project', 'clusterAgent')
+
+      expect(agent['id']).to eq(cluster_agent.to_global_id.to_s)
+      expect(agent['name']).to eq('agent-name')
+      expect(agent['createdAt']).to be_present
+      expect(agent['updatedAt']).to be_present
+      expect(agent['project']['id']).to eq(project.to_global_id.to_s)
+    end
+  end
 end

spec/models/clusters/agent_spec.rb

@@ -12,6 +12,17 @@ RSpec.describe Clusters::Agent do
   it { is_expected.to validate_length_of(:name).is_at_most(63) }
   it { is_expected.to validate_uniqueness_of(:name).scoped_to(:project_id) }
 
+  describe 'scopes' do
+    describe '.with_name' do
+      let!(:matching_name) { create(:cluster_agent, name: 'matching-name') }
+      let!(:other_name) { create(:cluster_agent, name: 'other-name') }
+
+      subject { described_class.with_name(matching_name.name) }
+
+      it { is_expected.to contain_exactly(matching_name) }
+    end
+  end
+
   describe 'validation' do
     describe 'name validation' do
       it 'rejects names that do not conform to RFC 1123', :aggregate_failures do