fix: GraphQL validate events

Fix the logic for adding `graphql.validation.error` events on `validate` spans.

The `errors` variable would always end up being a serialized `"[]"`
empty array which wasn't nil and an empty `graphql.validation.error`
event would be added.

Author: swalkinshaw

instrumentation/graphql/lib/opentelemetry/instrumentation/graphql/tracers/graphql_trace.rb

@@ -36,12 +36,13 @@ def parse(query_string:, &block)
           def validate(query:, validate:, &block)
             tracer.in_span('graphql.validate') do |span|
               super.tap do |response|
-                errors = response[:errors]&.compact&.map(&:to_h)&.to_json
-                unless errors.nil?
+                errors = response[:errors]&.compact&.map(&:to_h) || []
+
+                unless errors.empty?
                   span.add_event(
                     'graphql.validation.error',
                     attributes: {
-                      'message' => errors
+                      'message' => errors.to_json
                     }
                   )
                 end

instrumentation/graphql/lib/opentelemetry/instrumentation/graphql/tracers/graphql_tracer.rb

@@ -29,12 +29,15 @@ def platform_trace(platform_key, key, data) # rubocop:disable Metrics/Cyclomatic
 
             tracer.in_span(platform_key, attributes: attributes_for(key, data)) do |span|
               yield.tap do |response|
-                errors = response[:errors]&.compact&.map(&:to_h)&.to_json if key == 'validate'
-                unless errors.nil?
+                next unless key == 'validate'
+
+                errors = response[:errors]&.compact&.map(&:to_h) || []
+
+                unless errors.empty?
                   span.add_event(
                     'graphql.validation.error',
                     attributes: {
-                      'message' => errors
+                      'message' => errors.to_json
                     }
                   )
                 end

instrumentation/graphql/test/instrumentation/graphql/tracers/graphql_tracing_test.rb

@@ -252,21 +252,30 @@
       end
     end
 
-    it 'traces validate with events' do
-      SomeGraphQLAppSchema.execute(
-        <<-GRAPHQL
-          {
-            nonExistentField
-          }
-        GRAPHQL
-      )
-      span = spans.find { |s| s.name == 'graphql.validate' }
-      event = span.events.find { |e| e.name == 'graphql.validation.error' }
-      # rubocop:disable Layout/LineLength
-      _(event.attributes['message']).must_equal(
-        "[{\"message\":\"Field 'nonExistentField' doesn't exist on type 'Query'\",\"locations\":[{\"line\":2,\"column\":13}],\"path\":[\"query\",\"nonExistentField\"],\"extensions\":{\"code\":\"undefinedField\",\"typeName\":\"Query\",\"fieldName\":\"nonExistentField\"}}]"
-      )
-      # rubocop:enable Layout/LineLength
+    describe 'validate spans' do
+      it 'adds events for validation errors' do
+        SomeGraphQLAppSchema.execute(
+          <<-GRAPHQL
+            {
+              nonExistentField
+            }
+          GRAPHQL
+        )
+        span = spans.find { |s| s.name == 'graphql.validate' }
+        event = span.events.find { |e| e.name == 'graphql.validation.error' }
+        # rubocop:disable Layout/LineLength
+        _(event.attributes['message']).must_equal(
+          "[{\"message\":\"Field 'nonExistentField' doesn't exist on type 'Query'\",\"locations\":[{\"line\":2,\"column\":15}],\"path\":[\"query\",\"nonExistentField\"],\"extensions\":{\"code\":\"undefinedField\",\"typeName\":\"Query\",\"fieldName\":\"nonExistentField\"}}]"
+        )
+        # rubocop:enable Layout/LineLength
+      end
+
+      it 'does not add events for valid documents' do
+        SomeGraphQLAppSchema.execute('{ vehicle { __typename } }')
+
+        span = spans.find { |s| s.name == 'graphql.validate' }
+        _(span.events).must_be_nil
+      end
     end
   end