Add CreateComponent mutation to allow components to be added to a project

app/graphql/mutations/create_component.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module Mutations
+  class CreateComponent < BaseMutation
+    description 'A mutation to create a new component'
+    input_object_class Types::CreateComponentInputType
+
+    field :component, Types::ComponentType, description: 'The component that has been created'
+
+    def resolve(**input)
+      project = GlobalID.find(input[:project_id])
+
+      raise GraphQL::ExecutionError, 'Project not found' unless project
+
+      component = Component.new input
+      component.project = project
+
+      unless context[:current_ability].can?(:create, component)
+        raise GraphQL::ExecutionError,
+              'You are not permitted to update this component'
+      end
+
+      return { component: } if component.save
+
+      raise GraphQL::ExecutionError, component.errors.full_messages.join(', ')
+    end
+
+    def ready?(**_args)
+      if context[:current_ability]&.can?(:create, Component, Project.new(user_id: context[:current_user_id]))
+        return true
+      end
+
+      raise GraphQL::ExecutionError, 'You are not permitted to create a component'
+    end
+  end
+end

app/graphql/types/create_component_input_type.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Types
+  class CreateComponentInputType < Types::BaseInputObject
+    description 'Represents a component during creation'
+
+    argument :content, String, required: false, description: 'The text content of the component'
+    argument :default, Boolean, required: true, description: 'If this is the default component on a project'
+    argument :extension, String, required: true, description: 'The file extension of the component, e.g. html, csv, py'
+    argument :name, String, required: true, description: 'The name of the file'
+    argument :project_id, String, required: true, description: 'The easy-to-rememeber identifier of the project'
+  end
+end

app/graphql/types/mutation_type.rb

@@ -2,9 +2,12 @@
 
 module Types
   class MutationType < Types::BaseObject
+    # rubocop:disable GraphQL/ExtractType
+    field :create_component, mutation: Mutations::CreateComponent, description: 'Create a component'
     field :create_project, mutation: Mutations::CreateProject, description: 'Create a project, complete with components'
     field :delete_project, mutation: Mutations::DeleteProject, description: 'Delete an existing project'
     field :remix_project, mutation: Mutations::RemixProject, description: 'Remix a project'
     field :update_project, mutation: Mutations::UpdateProject, description: 'Update fields on an existing project'
+    # rubocop:enable GraphQL/ExtractType
   end
 end

db/schema.graphql

@@ -83,6 +83,56 @@ type ComponentEdge {
   node: Component
 }
 
+"""
+Represents a component during creation
+"""
+input CreateComponentInput {
+  """
+  A unique identifier for the client performing the mutation.
+  """
+  clientMutationId: String
+
+  """
+  The text content of the component
+  """
+  content: String
+
+  """
+  If this is the default component on a project
+  """
+  default: Boolean!
+
+  """
+  The file extension of the component, e.g. html, csv, py
+  """
+  extension: String!
+
+  """
+  The name of the file
+  """
+  name: String!
+
+  """
+  The easy-to-rememeber identifier of the project
+  """
+  projectId: String!
+}
+
+"""
+Autogenerated return type of CreateComponent.
+"""
+type CreateComponentPayload {
+  """
+  A unique identifier for the client performing the mutation.
+  """
+  clientMutationId: String
+
+  """
+  The component that has been created
+  """
+  component: Component
+}
+
 """
 Represents a project during creation
 """
@@ -219,6 +269,16 @@ type ImageEdge {
 }
 
 type Mutation {
+  """
+  Create a component
+  """
+  createComponent(
+    """
+    Parameters for CreateComponent
+    """
+    input: CreateComponentInput!
+  ): CreateComponentPayload
+
   """
   Create a project, complete with components
   """

spec/graphql/mutations/create_component_mutation_spec.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe 'mutation CreateComponent() { ... }' do
+  subject(:result) { execute_query(query: mutation, variables:) }
+
+  let(:project) { create(:project) }
+  let(:project_id) { project.to_gid_param }
+
+  let(:mutation) { 'mutation CreateComponent($component: CreateComponentInput!) { createComponent(input: $component) { component { id } } }' }
+  # let(:project_id) { 'dummy-id' }
+  let(:variables) do
+    {
+      component: {
+        projectId: project_id,
+        name: 'test',
+        extension: 'py',
+        content: 'blah',
+        default: false
+      }
+    }
+  end
+
+  it { expect(mutation).to be_a_valid_graphql_query }
+
+  context 'when unauthenticated' do
+    it 'does not create a component' do
+      expect { result }.not_to change(Component, :count)
+    end
+
+    it 'returns an error' do
+      expect(result.dig('errors', 0, 'message')).not_to be_blank
+    end
+  end
+
+  context 'when the graphql context is unset' do
+    let(:graphql_context) { nil }
+
+    it 'does not create a component' do
+      expect { result }.not_to change(Component, :count)
+    end
+  end
+
+  context 'when authenticated' do
+    let(:current_user_id) { SecureRandom.uuid }
+    let(:project) { create(:project, user_id: current_user_id) }
+
+    it 'returns the component ID' do
+      expect(result.dig('data', 'createComponent', 'component', 'id')).not_to be_nil
+    end
+
+    context 'when project id doesnt exist' do
+      let(:project_id) { 'dummy-id' }
+
+      it 'returns an error' do
+        expect(result.dig('errors', 0, 'message')).not_to be_blank
+      end
+    end
+
+    context 'when project id exists but belongs to someone else' do
+      let(:project) { create(:project) }
+
+      it 'returns an error' do
+        expect(result.dig('errors', 0, 'message')).not_to be_blank
+      end
+    end
+
+    context 'when project component fails to save' do
+      before do
+        component = Component.new
+        allow(component).to receive(:save).and_return(false)
+        allow(Component).to receive(:new).and_return(component)
+      end
+
+      it 'returns an error' do
+        expect(result.dig('errors', 0, 'message')).not_to be_nil
+      end
+    end
+  end
+end