Prefer selected_operation_name over operation_name.

`GraphQL::Query#operation_name` is initially only set to what's passed
into `GraphQL::Query.new`. For a query which has only one operation,
it gets populated later when the query AST is parsed:

https://github.com/rmosolgo/graphql-ruby/blob/v2.5.18/lib/graphql/query.rb#L489-L491

`GraphQL::Query#selected_operation_name` is safer to use--it parses the
AST when called and will therefore only be `nil` if there truely is no
selected operation name:

https://github.com/rmosolgo/graphql-ruby/blob/v2.5.18/lib/graphql/query.rb#L115-L118
https://github.com/rmosolgo/graphql-ruby/blob/v2.5.18/lib/graphql/query.rb#L294-L299

Since `selected_operation_name` is safer than `operation_name`, we want
to use it everywhere.

Author: myronmarston

elasticgraph-graphql/lib/elastic_graph/graphql/query_executor.rb

@@ -65,7 +65,7 @@ def execute(
 
         unless result.to_h.fetch("errors", []).empty?
           @logger.error <<~EOS
-            Query #{query.operation_name}[1] for client #{client.description} resulted in errors[2].
+            Query #{query.selected_operation_name}[1] for client #{client.description} resulted in errors[2].
 
             [1] #{full_description_of(query)}
 
@@ -79,7 +79,7 @@ def execute(
         # returns `nil` on an invalid query, and I don't want to risk leaking PII by logging the raw query string, so
         # we don't log any form of the query in that case.
         if duration > @slow_query_threshold_ms
-          @logger.warn "Query #{query.operation_name} for client #{client.description} with shard routing values " \
+          @logger.warn "Query #{query.selected_operation_name} for client #{client.description} with shard routing values " \
             "#{query_tracker.shard_routing_values.sort.inspect} and search index expressions #{query_tracker.search_index_expressions.sort.inspect} took longer " \
             "(#{duration} ms) than the configured slow query threshold (#{@slow_query_threshold_ms} ms). " \
             "Sanitized query:\n\n#{query.sanitized_query_string}"
@@ -90,7 +90,7 @@ def execute(
             "message_type" => "ElasticGraphQueryExecutorQueryDuration",
             "client" => client.name,
             "query_fingerprint" => fingerprint_for(query),
-            "query_name" => query.operation_name,
+            "query_name" => query.selected_operation_name,
             "duration_ms" => duration,
             # How long the datastore queries took according to what the datastore itself reported.
             "datastore_server_duration_ms" => query_tracker.datastore_query_server_duration_ms,
@@ -147,7 +147,7 @@ def execute_query(query, client:)
         query.result
       rescue => ex
         @logger.error <<~EOS
-          Query #{query.operation_name}[1] for client #{client.description} failed with an exception[2].
+          Query #{query.selected_operation_name}[1] for client #{client.description} failed with an exception[2].
 
           [1] #{full_description_of(query)}
 

elasticgraph-graphql/sig/graphql_gem.rbs

@@ -105,7 +105,11 @@ module GraphQL
     ) -> void
 
     attr_reader document: Language::Nodes::Document
-    attr_reader operation_name: ::String?
+
+    # Commented out to discourage use--`selected_operation_name` should be preferred since `operation_name`
+    # may only be populated after the query AST is parsed.
+    # attr_reader operation_name: ::String?
+
     attr_reader operations: ::Hash[::String, Language::Nodes::OperationDefinition]
     attr_reader fingerprint: ::String
     attr_reader sanitized_query_string: ::String?