[Feature]: Add support for client credentials grant

CHANGELOG.md

@@ -3,6 +3,8 @@
 Note: For changes to the API, see https://shopify.dev/changelog?filter=api
 ## Unreleased
 
+- [#1362](https://github.com/Shopify/shopify-api-ruby/pull/1362) Add support for client credentials grant
+
 ## 14.8.0
 
 - [#1355](https://github.com/Shopify/shopify-api-ruby/pull/1355) Add support for 2025-01 API version

docs/usage/oauth.md

@@ -11,7 +11,8 @@ For more information on authenticating a Shopify app please see the [Types of Au
 - [Note about Rails](#note-about-rails)
 - [Performing OAuth](#performing-oauth-1)
   - [Token Exchange](#token-exchange)
-  - [Authorization Code Grant Flow](#authorization-code-grant-flow)
+  - [Authorization Code Grant](#authorization-code-grant)
+  - [Client Credentials Grant](#client-credentials-grant)
 - [Using OAuth Session to make authenticated API calls](#using-oauth-session-to-make-authenticated-api-calls)
 
 ## Session Persistence
@@ -31,10 +32,14 @@ with [token exchange](#token-exchange) instead of the authorization code grant f
     - Recommended and is only available for embedded apps
     - Doesn't require redirects, which makes authorization faster and prevents flickering when loading the app
     - Access scope changes are handled by [Shopify managed installation](https://shopify.dev/docs/apps/auth/installation#shopify-managed-installation)
-2. [Authorization Code Grant Flow](#authorization-code-grant-flow)
+2. [Authorization Code Grant](#authorization-code-grant)
     - OAuth flow that requires the app to redirect the user to Shopify for installation/authorization of the app to access the shop's data.
     - Suitable for non-embedded apps
     - Installations, and access scope changes are managed by the app
+3. [Client Credentials Grant](#client-credentials-grant)
+    - Suitable for apps without a UI
+    - Doesn't require user interaction in the browser
+    - Access scope changes are handled by [Shopify managed installation](https://shopify.dev/docs/apps/auth/installation#shopify-managed-installation)
 
 ## Note about Rails
 If using in the Rails framework, we highly recommend you use the [shopify_app](https://github.com/Shopify/shopify_app) gem to perform OAuth, you won't have to follow the instructions below to start your own OAuth flow.
@@ -94,7 +99,7 @@ end
 
 ```
 
-### Authorization Code Grant Flow
+### Authorization Code Grant
 ##### Steps
 1. [Add a route to start OAuth](#1-add-a-route-to-start-oauth)
 2. [Add an Oauth callback route](#2-add-an-oauth-callback-route)
@@ -265,9 +270,41 @@ def callback
   end
 end
 ```
-
 ⚠️ You can see a concrete example in the `ShopifyApp` gem's [CallbackController](https://github.com/Shopify/shopify_app/blob/main/app/controllers/shopify_app/callback_controller.rb).
 
+### Client Credentials Grant
+
+> [!NOTE]
+> You can only use the client credentials grant when building apps for your own organization.
+
+> [!WARNING]
+> [token exchange](#token-exchange) (for embedded apps) or the [authorization code grant](#authorization-code-grant) should be used instead of the client credentials grant, if your app is a browser based web app.
+
+#### Perform Client Credentials Grant
+Use [`ShopifyAPI::Auth::ClientCredentials`](https://github.com/Shopify/shopify-api-ruby/blob/main/lib/shopify_api/auth/client_credentials.rb) to
+exchange the [app's client ID and client secret](https://shopify.dev/docs/apps/build/authentication-authorization/client-secrets) for an access token.
+#### Input
+| Parameter      | Type                   | Required? | Default Value | Notes                                                                                                       |
+| -------------- | ---------------------- | :-------: | :-----------: | ----------------------------------------------------------------------------------------------------------- |
+| `shop`         | `String` | Yes | - | A Shopify domain name in the form `{exampleshop}.myshopify.com`. |
+
+#### Output
+This method returns the new `ShopifyAPI::Auth::Session` object from the client credentials grant, your app should store this `Session` object to be used later [when making authenticated API calls](#using-oauth-session-to-make-authenticated-api-calls).
+
+#### Example
+```ruby
+
+# `shop` is the shop domain name - "this-is-my-example-shop.myshopify.com"
+
+def authenticate(shop)
+  session = ShopifyAPI::Auth::ClientCredentials.client_credentials(
+     shop: shop,
+   )
+  SessionRepository.store_session(session)
+end
+
+```
+
 ## Using OAuth Session to make authenticated API calls
 Once your OAuth flow is complete, and you have persisted your `Session` object, you may use that `Session` object to make authenticated API calls.
 

lib/shopify_api/auth/client_credentials.rb

@@ -0,0 +1,52 @@
+# typed: strict
+# frozen_string_literal: true
+
+module ShopifyAPI
+  module Auth
+    module ClientCredentials
+      extend T::Sig
+
+      CLIENT_CREDENTIALS_GRANT_TYPE = "client_credentials"
+
+      class << self
+        extend T::Sig
+
+        sig do
+          params(
+            shop: String,
+          ).returns(ShopifyAPI::Auth::Session)
+        end
+        def client_credentials(shop:)
+          unless ShopifyAPI::Context.setup?
+            raise ShopifyAPI::Errors::ContextNotSetupError,
+              "ShopifyAPI::Context not setup, please call ShopifyAPI::Context.setup"
+          end
+
+          shop_session = ShopifyAPI::Auth::Session.new(shop: shop)
+          body = {
+            client_id: ShopifyAPI::Context.api_key,
+            client_secret: ShopifyAPI::Context.api_secret_key,
+            grant_type: CLIENT_CREDENTIALS_GRANT_TYPE,
+          }
+
+          client = Clients::HttpClient.new(session: shop_session, base_path: "/admin/oauth")
+          response =
+            client.request(
+              Clients::HttpRequest.new(
+                http_method: :post,
+                path: "access_token",
+                body: body,
+                body_type: "application/json",
+              ),
+            )
+          response_hash = T.cast(response.body, T::Hash[String, T.untyped]).to_h
+
+          Session.from(
+            shop: shop,
+            access_token_response: Oauth::AccessTokenResponse.from_hash(response_hash),
+          )
+        end
+      end
+    end
+  end
+end

lib/shopify_api/auth/session.rb

@@ -95,13 +95,16 @@ def from(shop:, access_token_response:)
 
           if is_online
             associated_user = T.must(access_token_response.associated_user)
-            expires = Time.now + access_token_response.expires_in.to_i
             associated_user_scope = access_token_response.associated_user_scope
             id = "#{shop}_#{associated_user.id}"
           else
             id = "offline_#{shop}"
           end
 
+          if access_token_response.expires_in
+            expires = Time.now + access_token_response.expires_in.to_i
+          end
+
           new(
             id: id,
             shop: shop,

test/auth/client_credentials_test.rb

@@ -0,0 +1,52 @@
+# typed: false
+# frozen_string_literal: true
+
+require_relative "../test_helper"
+
+module ShopifyAPITest
+  module Auth
+    class ClientCredentialsTest < Test::Unit::TestCase
+      def setup
+        super()
+
+        @shop = "test-shop.myshopify.com"
+        @client_credentials_request = {
+          client_id: ShopifyAPI::Context.api_key,
+          client_secret: ShopifyAPI::Context.api_secret_key,
+          grant_type: "client_credentials",
+        }
+        @offline_token_response = {
+          access_token: SecureRandom.alphanumeric(10),
+          scope: "scope1,scope2",
+          expires_in: 1000,
+        }
+      end
+
+      def test_client_credentials_context_not_setup
+        modify_context(api_key: "", api_secret_key: "", host: "")
+
+        assert_raises(ShopifyAPI::Errors::ContextNotSetupError) do
+          ShopifyAPI::Auth::ClientCredentials.client_credentials(shop: @shop)
+        end
+      end
+
+      def test_client_credentials_offline_token
+        stub_request(:post, "https://#{@shop}/admin/oauth/access_token")
+          .with(body: @client_credentials_request)
+          .to_return(body: @offline_token_response.to_json, headers: { content_type: "application/json" })
+        expected_session = ShopifyAPI::Auth::Session.new(
+          id: "offline_#{@shop}",
+          shop: @shop,
+          access_token: @offline_token_response[:access_token],
+          scope: @offline_token_response[:scope],
+          is_online: false,
+          expires: Time.now + @offline_token_response[:expires_in].to_i,
+        )
+
+        session = ShopifyAPI::Auth::ClientCredentials.client_credentials(shop: @shop)
+
+        assert_equal(expected_session, session)
+      end
+    end
+  end
+end

test/auth/session_test.rb

@@ -79,7 +79,7 @@ def test_temp_with_block_var
         assert_equal(session, ShopifyAPI::Context.active_session)
       end
 
-      def test_from_with_offline_access_token_response
+      def test_from_with_offline_access_token_response_with_no_expires_in
         shop = "test-shop"
         response = ShopifyAPI::Auth::Oauth::AccessTokenResponse.new(
           access_token: "token",
@@ -103,6 +103,30 @@ def test_from_with_offline_access_token_response
         assert_equal(expected_session, session)
       end
 
+      def test_from_with_offline_access_token_response_with_expires_in
+        shop = "test-shop"
+        response = ShopifyAPI::Auth::Oauth::AccessTokenResponse.new(
+          access_token: "token",
+          scope: "scope1, scope2",
+          expires_in: 1000,
+        )
+
+        expected_session = ShopifyAPI::Auth::Session.new(
+          id: "offline_#{shop}",
+          shop: shop,
+          access_token: response.access_token,
+          scope: response.scope,
+          is_online: false,
+          associated_user_scope: nil,
+          associated_user: nil,
+          expires: Time.now + response.expires_in,
+          shopify_session_id: response.session,
+        )
+
+        session = ShopifyAPI::Auth::Session.from(shop: shop, access_token_response: response)
+        assert_equal(expected_session, session)
+      end
+
       def test_from_with_online_access_token_response
         shop = "test-shop"
         associated_user = ShopifyAPI::Auth::AssociatedUser.new(