lookahead.rb in graphql-2.1.4

- old
+ new

@@ -78,10 +78,26 @@
       # @return [Boolean]
       def selects?(field_name, selected_type: @selected_type, arguments: nil)
         selection(field_name, selected_type: selected_type, arguments: arguments).selected?
       end
 
+      # True if this node has a selection with alias matching `alias_name`.
+      # If `alias_name` is a String, it is treated as a GraphQL-style (camelized)
+      # field name and used verbatim. If `alias_name` is a Symbol, it is
+      # treated as a Ruby-style (underscored) name and camelized before comparing.
+      #
+      # If `arguments:` is provided, each provided key/value will be matched
+      # against the arguments in the next selection. This method will return false
+      # if any of the given `arguments:` are not present and matching in the next selection.
+      # (But, the next selection may contain _more_ than the given arguments.)
+      # @param alias_name [String, Symbol]
+      # @param arguments [Hash] Arguments which must match in the selection
+      # @return [Boolean]
+      def selects_alias?(alias_name, arguments: nil)
+        alias_selection(alias_name, arguments: arguments).selected?
+      end
+
       # @return [Boolean] True if this lookahead represents a field that was requested
       def selected?
         true
       end
 
@@ -103,36 +119,43 @@
               .possible_types(selected_type)
               .map { |t| @query.warden.fields(t) }
               .tap(&:flatten!)
           end
 
+
           if (match_by_orig_name = all_fields.find { |f| f.original_name == field_name })
             match_by_orig_name
           else
             # Symbol#name is only present on 3.0+
             sym_s = field_name.respond_to?(:name) ? field_name.name : field_name.to_s
             guessed_name = Schema::Member::BuildType.camelize(sym_s)
             @query.get_field(selected_type, guessed_name)
           end
         end
+        lookahead_for_selection(next_field_defn, selected_type, arguments)
+      end
 
-        if next_field_defn
-          next_nodes = []
-          @ast_nodes.each do |ast_node|
-            ast_node.selections.each do |selection|
-              find_selected_nodes(selection, next_field_defn, arguments: arguments, matches: next_nodes)
-            end
-          end
+      # Like {#selection}, but for aliases.
+      # It returns a null object (check with {#selected?})
+      # @return [GraphQL::Execution::Lookahead]
+      def alias_selection(alias_name, selected_type: @selected_type, arguments: nil)
+        alias_cache_key = [alias_name, arguments]
+        return alias_selections[key] if alias_selections.key?(alias_name)
 
-          if next_nodes.any?
-            Lookahead.new(query: @query, ast_nodes: next_nodes, field: next_field_defn, owner_type: selected_type)
-          else
-            NULL_LOOKAHEAD
-          end
-        else
-          NULL_LOOKAHEAD
+        alias_node = lookup_alias_node(ast_nodes, alias_name)
+        return NULL_LOOKAHEAD unless alias_node
+
+        next_field_defn = @query.get_field(selected_type, alias_node.name)
+
+        alias_arguments = @query.arguments_for(alias_node, next_field_defn)
+        if alias_arguments.is_a?(::GraphQL::Execution::Interpreter::Arguments)
+          alias_arguments = alias_arguments.keyword_arguments
         end
+
+        return NULL_LOOKAHEAD if arguments && arguments != alias_arguments
+
+        alias_selections[alias_cache_key] = lookahead_for_selection(next_field_defn, selected_type, alias_arguments, alias_name)
       end
 
       # Like {#selection}, but for all nodes.
       # It returns a list of Lookaheads for all Selections
       #
@@ -256,11 +279,11 @@
               on_type = @query.get_type(t.name)
               subselections_on_type = subselections_by_type[on_type] ||= {}
             end
             find_selections(subselections_by_type, subselections_on_type, on_type, ast_selection.selections, arguments)
           when GraphQL::Language::Nodes::FragmentSpread
-            frag_defn = @query.fragments[ast_selection.name] || raise("Invariant: Can't look ahead to nonexistent fragment #{ast_selection.name} (found: #{@query.fragments.keys})")
+            frag_defn = lookup_fragment(ast_selection)
             # Again, assuming a valid AST
             on_type = @query.get_type(frag_defn.type.name)
             subselections_on_type = subselections_by_type[on_type] ||= {}
             find_selections(subselections_by_type, subselections_on_type, on_type, frag_defn.selections, arguments)
           else
@@ -269,27 +292,27 @@
         end
       end
 
       # If a selection on `node` matches `field_name` (which is backed by `field_defn`)
       # and matches the `arguments:` constraints, then add that node to `matches`
-      def find_selected_nodes(node, field_defn, arguments:, matches:)
+      def find_selected_nodes(node, field_name, field_defn, arguments:, matches:, alias_name: NOT_CONFIGURED)
         return if skipped_by_directive?(node)
         case node
         when GraphQL::Language::Nodes::Field
-          if node.name == field_defn.graphql_name
+          if node.name == field_name && (NOT_CONFIGURED.equal?(alias_name) || node.alias == alias_name)
             if arguments.nil? || arguments.empty?
               # No constraint applied
               matches << node
             elsif arguments_match?(arguments, field_defn, node)
               matches << node
             end
           end
         when GraphQL::Language::Nodes::InlineFragment
-          node.selections.each { |s| find_selected_nodes(s, field_defn, arguments: arguments, matches: matches) }
+          node.selections.each { |s| find_selected_nodes(s, field_name, field_defn, arguments: arguments, matches: matches, alias_name: alias_name) }
         when GraphQL::Language::Nodes::FragmentSpread
-          frag_defn = @query.fragments[node.name] || raise("Invariant: Can't look ahead to nonexistent fragment #{node.name} (found: #{@query.fragments.keys})")
-          frag_defn.selections.each { |s| find_selected_nodes(s, field_defn, arguments: arguments, matches: matches) }
+          frag_defn = lookup_fragment(node)
+          frag_defn.selections.each { |s| find_selected_nodes(s, field_name, field_defn, arguments: arguments, matches: matches, alias_name: alias_name) }
         else
           raise "Unexpected selection comparison on #{node.class.name} (#{node})"
         end
       end
 
@@ -303,9 +326,53 @@
           end
 
           # Make sure the constraint is present with a matching value
           query_kwargs.key?(arg_name_sym) && query_kwargs[arg_name_sym] == arg_value
         end
+      end
+
+      def lookahead_for_selection(field_defn, selected_type, arguments, alias_name = NOT_CONFIGURED)
+        return NULL_LOOKAHEAD unless field_defn
+
+        next_nodes = []
+        field_name = field_defn.name
+        @ast_nodes.each do |ast_node|
+          ast_node.selections.each do |selection|
+            find_selected_nodes(selection, field_name, field_defn, arguments: arguments, matches: next_nodes, alias_name: alias_name)
+          end
+        end
+
+        return NULL_LOOKAHEAD if next_nodes.empty?
+
+        Lookahead.new(query: @query, ast_nodes: next_nodes, field: field_defn, owner_type: selected_type)
+      end
+
+      def alias_selections
+        return @alias_selections if defined?(@alias_selections)
+        @alias_selections ||= {}
+      end
+
+      def lookup_alias_node(nodes, name)
+        return if nodes.empty?
+
+        nodes.flat_map(&:children)
+             .flat_map { |child| unwrap_fragments(child) }
+             .find { |child| child.is_a?(GraphQL::Language::Nodes::Field) && child.alias == name }
+      end
+
+      def unwrap_fragments(node)
+        case node
+        when GraphQL::Language::Nodes::InlineFragment
+          node.children
+        when GraphQL::Language::Nodes::FragmentSpread
+          lookup_fragment(node).children
+        else
+          [node]
+        end
+      end
+
+      def lookup_fragment(ast_selection)
+        @query.fragments[ast_selection.name] || raise("Invariant: Can't look ahead to nonexistent fragment #{ast_selection.name} (found: #{@query.fragments.keys})")
       end
     end
   end
 end