Handle exceptions outside the GraphQL schema

This allows us to report JSON parse exceptions to clients and ignore
them in sentry.

1 files changed, 17 insertions, 21 deletions

diff --git a/app/controllers/graphql_controller.rb b/app/controllers/graphql_controller.rb
index ef258bf07cb..0a1cf169aca 100644
--- a/app/controllers/graphql_controller.rb
+++ b/app/controllers/graphql_controller.rb
@@ -5,7 +5,7 @@ class GraphqlController < ApplicationController
   before_action :check_graphql_feature_flag!
 
   def execute
-    variables = ensure_hash(params[:variables])
+    variables = Gitlab::Graphql::Variables.new(params[:variables]).to_h
     query = params[:query]
     operation_name = params[:operationName]
     context = {
@@ -15,35 +15,31 @@ class GraphqlController < ApplicationController
     render json: result
   end
 
+  rescue_from StandardError do |exception|
+    log_exception(exception)
+
+    render_error("Internal server error")
+  end
+
+  rescue_from Gitlab::Graphql::Variables::Invalid do |exception|
+    render_error(exception.message, status: :unprocessable_entity)
+  end
+
   private
 
   # Overridden from the ApplicationController to make the response look like
   # a GraphQL response. That is nicely picked up in Graphiql.
   def render_404
-    error = { errors: [ message: "Not found" ] }
+    render_error("Not found!", status: :not_found)
+  end
+
+  def render_error(message, status: 500)
+    error = { errors: [message: message] }
 
-    render json: error, status: :not_found
+    render json: error, status: status
   end
 
   def check_graphql_feature_flag!
     render_404 unless Feature.enabled?(:graphql)
   end
-
-  # Handle form data, JSON body, or a blank value
-  def ensure_hash(ambiguous_param)
-    case ambiguous_param
-    when String
-      if ambiguous_param.present?
-        ensure_hash(JSON.parse(ambiguous_param))
-      else
-        {}
-      end
-    when Hash, ActionController::Parameters
-      ambiguous_param
-    when nil
-      {}
-    else
-      raise ArgumentError, "Unexpected parameter: #{ambiguous_param}"
-    end
-  end
 end