Gracefully handle HTTP 204 response bodies (#1098)

* Gracefully handle HTTP 204 response bodies

* Add changelog entry for #1098

* Fix up changelog formatting

* Rubocop fixup

CHANGELOG.md

@@ -3,6 +3,8 @@
 Note: For changes to the API, see https://shopify.dev/changelog?filter=api
 
 ## Unreleased
+
+- [#1098](https://github.com/Shopify/shopify-api-ruby/pull/1098) Gracefully handle HTTP 204 repsonse bodies
 - [#1104](https://github.com/Shopify/shopify-api-ruby/pull/1104) Allow api version overrides.
 
 ## Version 12.4.0

lib/shopify_api/clients/http_client.rb

@@ -48,7 +48,7 @@ def request(request)
             body: request.body.class == Hash ? T.unsafe(request.body).to_json : request.body,
           ), HTTParty::Response)
 
-          body = res.body.empty? ? {} : JSON.parse(res.body)
+          body = res.body.nil? || res.body.empty? ? {} : JSON.parse(res.body)
           response = HttpResponse.new(code: res.code.to_i, headers: res.headers.to_h, body: body)
 
           if response.headers["x-shopify-api-deprecated-reason"]

test/clients/http_client_test.rb

@@ -71,6 +71,20 @@ def test_request_with_empty_response_body
         verify_http_request
       end
 
+      # It doesn't really make sense for an HTTP body to ever be `nil`, but
+      # the underlying HTTParty library seems to use `nil` for the response
+      # body in situations where it doesn't need to parse it, e.g. when the
+      # response status is 204.
+      def test_request_with_nil_response_body
+        @success_body = {}
+
+        stub_request(@request.http_method, "https://#{@shop}#{@base_path}/#{@request.path}")
+          .with(body: @request.body.to_json, query: @request.query, headers: @expected_headers)
+          .to_return(body: "", headers: @response_headers, status: 204)
+
+        verify_http_request
+      end
+
       def test_request_with_no_access_token
         @session = ShopifyAPI::Auth::Session.new(shop: @shop)
         @client = ShopifyAPI::Clients::HttpClient.new(session: @session, base_path: @base_path)