Report useful error message in missing parameter

app/controllers/api/v1/base_controller.rb

@@ -19,6 +19,7 @@ module Api
       rescue_from CanCan::AccessDenied, with: :unauthorized
       rescue_from ActiveRecord::RecordNotFound, with: :not_found
       rescue_from Pagy::VariableError, with: :invalid_pagination
+      rescue_from ActionController::ParameterMissing, with: :missing_parameter
       rescue_from ActionController::UnpermittedParameters, with: :unpermitted_parameters
 
       private
@@ -62,6 +63,13 @@ module Api
                json: json_api_error(exception.message)
       end
 
+      def missing_parameter(error)
+        message = I18n.t(:missing_parameter, param: error.param, scope: :api)
+
+        render status: :unprocessable_entity,
+               json: json_api_error(message)
+      end
+
       def unpermitted_parameters(error)
         message = I18n.t(:unpermitted_parameters, params: error.params.join(", "), scope: :api)
 

config/locales/en.yml

@@ -1413,6 +1413,7 @@ en:
     invalid_api_key: "Invalid API key (%{key}) specified."
     unauthorized: "You are not authorized to perform that action."
     unpermitted_parameters: "Parameters not allowed in this request: %{params}"
+    missing_parameter: "A required parameter is missing or empty: %{param}"
     invalid_resource: "Invalid resource. Please fix errors and try again."
     resource_not_found: "The resource you were looking for could not be found."
     enterprise_logo:

spec/requests/api/v1/customers_spec.rb

@@ -161,7 +161,10 @@ describe "Customers", type: :request do
         param(:customer) { {} }
         schema "$ref": "#/components/schemas/error_response"
 
-        run_test!
+        run_test! do
+          expect(json_error_detail).to eq "A required parameter is missing or empty: customer"
+          expect(json_response[:meta]).to eq nil
+        end
       end
     end
   end