Add user root query to GraphQL API

Adds a root user query to search
for a user by username or id

app/graphql/resolvers/user_resolver.rb

+# frozen_string_literal: true
+
+module Resolvers
+  class UserResolver < BaseResolver
+    description 'Retrieve a single user'
+
+    argument :id, GraphQL::ID_TYPE,
+             required: false,
+             description: 'ID of the User'
+
+    argument :username, GraphQL::STRING_TYPE,
+             required: false,
+             description: 'Username of the User'
+
+    def resolve(id: nil, username: nil)
+      id_or_username = GitlabSchema.parse_gid(id, expected_type: ::User).model_id if id
+      id_or_username ||= username
+
+      ::UserFinder.new(id_or_username).find_by_id_or_username
+    end
+
+    def ready?(id: nil, username: nil)
+      unless id.present? ^ username.present?
+        raise Gitlab::Graphql::Errors::ArgumentError, 'Provide either a single username or id'
+      end
+
+      super
+    end
+  end
+end

app/graphql/types/query_type.rb

@@ -47,6 +47,11 @@ class QueryType < ::Types::BaseObject
           null: false,
           description: 'Fields related to design management'
+    field :user, Types::UserType,
+          null: true,
+          description: 'Find a user',
+          resolver: Resolvers::UserResolver
+
     field :echo, GraphQL::STRING_TYPE, null: false,
           description: 'Text to echo back',
           resolver: Resolvers::EchoResolver

changelogs/unreleased/215658-add-users-graphql.yml

+---
+title: Add user root query to GraphQL API
+merge_request: 33041
+author:
+type: added

doc/api/graphql/index.md

@@ -57,6 +57,7 @@ The GraphQL API includes the following queries at the root level:
 1. `project` : Project information, with many of its associations such as issues and merge requests.
 1. `group` : Basic group information and epics **(ULTIMATE)** are currently supported.
+1. `user` : Information about a particular user.
 1. `namespace` : Within a namespace it is also possible to fetch `projects`.
 1. `currentUser`: Information about the currently logged in user.
 1. `metaData`: Metadata about GitLab and the GraphQL API.

doc/api/graphql/reference/gitlab_schema.graphql

@@ -9142,6 +9142,21 @@ type Query {
     visibility: VisibilityScopesEnum
   ): SnippetConnection
+  """
+  Find a user
+  """
+  user(
+    """
+    ID of the User
+    """
+    id: ID
+
+    """
+    Username of the User
+    """
+    username: String
+  ): User
+
   """
   Vulnerabilities reported on projects on the current user's instance security dashboard
   """

doc/api/graphql/reference/gitlab_schema.json

@@ -26833,6 +26833,39 @@
               "isDeprecated": false,
               "deprecationReason": null
             },
+            {
+              "name": "user",
+              "description": "Find a user",
+              "args": [
+                {
+                  "name": "id",
+                  "description": "ID of the User",
+                  "type": {
+                    "kind": "SCALAR",
+                    "name": "ID",
+                    "ofType": null
+                  },
+                  "defaultValue": null
+                },
+                {
+                  "name": "username",
+                  "description": "Username of the User",
+                  "type": {
+                    "kind": "SCALAR",
+                    "name": "String",
+                    "ofType": null
+                  },
+                  "defaultValue": null
+                }
+              ],
+              "type": {
+                "kind": "OBJECT",
+                "name": "User",
+                "ofType": null
+              },
+              "isDeprecated": false,
+              "deprecationReason": null
+            },
             {
               "name": "vulnerabilities",
               "description": "Vulnerabilities reported on projects on the current user's instance security dashboard",

spec/graphql/resolvers/user_resolver_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Resolvers::UserResolver do
+  include GraphqlHelpers
+
+  describe '#resolve' do
+    let_it_be(:user) { create(:user) }
+
+    context 'when neither an ID or a username is provided' do
+      it 'raises an ArgumentError' do
+        expect { resolve_user }
+        .to raise_error(Gitlab::Graphql::Errors::ArgumentError)
+      end
+    end
+
+    it 'raises an ArgumentError when both an ID and username are provided' do
+      expect { resolve_user(id: user.to_global_id, username: user.username) }
+        .to raise_error(Gitlab::Graphql::Errors::ArgumentError)
+    end
+
+    context 'by username' do
+      it 'returns the correct user' do
+        expect(
+          resolve_user(username: user.username)
+        ).to eq(user)
+      end
+    end
+
+    context 'by ID' do
+      it 'returns the correct user' do
+        expect(
+          resolve_user(id: user.to_global_id)
+        ).to eq(user)
+      end
+    end
+  end
+
+  private
+
+  def resolve_user(args = {})
+    resolve(described_class, args: args)
+  end
+end

spec/graphql/types/query_type_spec.rb

@@ -8,9 +8,24 @@
   end
   it 'has the expected fields' do
-    expected_fields = %i[project namespace group echo metadata current_user snippets design_management]
-
-    expect(described_class).to have_graphql_fields(*expected_fields).at_least
+    expected_fields = %i[
+      current_user
+      design_management
+      geoNode
+      group
+      echo
+      instanceSecurityDashboard
+      metadata
+      namespace
+      project
+      projects
+      snippets
+      user
+      vulnerabilities
+      vulnerabilitiesCountByDayAndSeverity
+    ]
+
+    expect(described_class).to have_graphql_fields(*expected_fields)
   end
   describe 'namespace field' do

spec/requests/api/graphql/user_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe 'User' do
+  include GraphqlHelpers
+
+  let_it_be(:current_user) { create(:user) }
+
+  shared_examples 'a working user query' do
+    it_behaves_like 'a working graphql query' do
+      before do
+        post_graphql(query, current_user: current_user)
+      end
+    end
+
+    it 'includes the user' do
+      post_graphql(query, current_user: current_user)
+
+      expect(graphql_data['user']).not_to be_nil
+    end
+
+    it 'returns no user when global restricted_visibility_levels includes PUBLIC' do
+      stub_application_setting(restricted_visibility_levels: [Gitlab::VisibilityLevel::PUBLIC])
+
+      post_graphql(query)
+
+      expect(graphql_data['user']).to be_nil
+    end
+  end
+
+  context 'when id parameter is used' do
+    let(:query) { graphql_query_for(:user, { id: current_user.to_global_id.to_s }) }
+
+    it_behaves_like 'a working user query'
+  end
+
+  context 'when username parameter is used' do
+    let(:query) { graphql_query_for(:user, { username: current_user.username.to_s }) }
+
+    it_behaves_like 'a working user query'
+  end
+
+  context 'when username and id parameter are used' do
+    let_it_be(:query) { graphql_query_for(:user, { id: current_user.to_global_id.to_s, username: current_user.username }, 'id') }
+
+    it 'displays an error' do
+      post_graphql(query)
+
+      expect(graphql_errors).to include(
+        a_hash_including('message' => a_string_matching(%r{Provide either a single username or id}))
+      )
+    end
+  end
+end