Add GraphQL::Query::Partial

lib/graphql/execution/interpreter.rb

@@ -26,7 +26,7 @@ def run_all(schema, query_options, context: {}, max_complexity: schema.max_compl
             query = case opts
             when Hash
               schema.query_class.new(schema, nil, **opts)
-            when GraphQL::Query
+            when GraphQL::Query, GraphQL::Query::Partial
               opts
             else
               raise "Expected Hash or GraphQL::Query, not #{opts.class} (#{opts.inspect})"
@@ -149,6 +149,62 @@ def run_all(schema, query_options, context: {}, max_complexity: schema.max_compl
             end
           end
         end
+
+        def run_partials(schema, partials, context:)
+          multiplex = Execution::Multiplex.new(schema: schema, queries: partials, context: context, max_complexity: nil)
+          dataloader = multiplex.dataloader
+          lazies_at_depth = Hash.new { |h, k| h[k] = [] }
+
+          partials.each do |partial|
+            dataloader.append_job {
+              runtime = Runtime.new(query: partial, lazies_at_depth: lazies_at_depth)
+              partial.context.namespace(:interpreter_runtime)[:runtime] = runtime
+              # TODO tracing?
+              runtime.run_partial_eager
+            }
+          end
+
+          dataloader.run
+
+          dataloader.append_job {
+            partials.each do |partial|
+              runtime = partial.context.namespace(:interpreter_runtime)[:runtime]
+              runtime.final_result
+            end
+            # TODO tracing?
+            Interpreter::Resolve.resolve_each_depth(lazies_at_depth, multiplex.dataloader)
+          }
+
+          dataloader.run
+
+          partials.map do |partial|
+            # Assign the result so that it can be accessed in instrumentation
+            data_result = partial.context.namespace(:interpreter_runtime)[:runtime].final_result
+            partial.result_values = if data_result.equal?(NO_OPERATION)
+              if !partial.context.errors.empty?
+                { "errors" => partial.context.errors.map(&:to_h) }
+              else
+                data_result
+              end
+            else
+              result = {}
+
+              if !partial.context.errors.empty?
+                error_result = partial.context.errors.map(&:to_h)
+                result["errors"] = error_result
+              end
+
+              result["data"] = data_result
+
+              result
+            end
+            if partial.context.namespace?(:__query_result_extensions__)
+              partial.result_values["extensions"] = partial.context.namespace(:__query_result_extensions__)
+            end
+            # Partial::Result
+            partial.result
+          end
+        end
       end
 
       class ListResultFailedError < GraphQL::Error

lib/graphql/execution/interpreter/runtime.rb

@@ -108,6 +108,101 @@ def run_eager
           nil
         end
 
+        # @return [void]
+        def run_partial_eager
+          # `query` is actually a GraphQL::Query::Partial
+          partial = query
+          root_type = partial.root_type
+          object = partial.object
+          selections = partial.ast_nodes.map(&:selections).inject(&:+)
+          runtime_state = get_current_runtime_state
+          case root_type.kind.name
+          when "OBJECT"
+            object_proxy = root_type.wrap(object, context)
+            object_proxy = schema.sync_lazy(object_proxy)
+            @response = GraphQLResultHash.new(nil, root_type, object_proxy, nil, false, selections, false, partial.ast_nodes.first, nil, nil)
+            each_gathered_selections(@response) do |selections, is_selection_array, ordered_result_keys|
+              @response.ordered_result_keys ||= ordered_result_keys
+              if is_selection_array == true
+                raise "This isn't supported yet"
+              end
+
+              @dataloader.append_job {
+                evaluate_selections(
+                  selections,
+                  @response,
+                  nil,
+                  runtime_state,
+                )
+              }
+            end
+          when "LIST"
+            inner_type = root_type.unwrap
+            case inner_type.kind.name
+            when "SCALAR", "ENUM"
+              parent_object_proxy = partial.parent_type.wrap(object, context)
+              parent_object_proxy = schema.sync_lazy(parent_object_proxy)
+              field_node = partial.ast_nodes.first
+              result_name = field_node.alias || field_node.name
+              @response = GraphQLResultHash.new(nil, partial.parent_type, parent_object_proxy, nil, false, nil, false, field_node, nil, nil)
+              @response.ordered_result_keys = [result_name]
+              evaluate_selection(result_name, partial.ast_nodes, @response)
+            else
+              @response = GraphQLResultArray.new(nil, root_type, nil, nil, false, selections, false, field_node, nil, nil)
+              idx = nil
+              object.each do |inner_value|
+                idx ||= 0
+                this_idx = idx
+                idx += 1
+                @dataloader.append_job do
+                  runtime_state.current_result_name = this_idx
+                  runtime_state.current_result = @response
+                  continue_field(
+                    inner_value, root_type, nil, inner_type, nil, @response.graphql_selections, false, object_proxy,
+                    nil, this_idx, @response, false, runtime_state
+                  )
+                end
+              end
+            end
+          when "SCALAR", "ENUM"
+            parent_type = partial.parent_type
+            # TODO what if not object type? Maybe returns a lazy here.
+            parent_object_type, object = resolve_type(parent_type, object)
+            parent_object_proxy = parent_object_type.wrap(object, context)
+            parent_object_proxy = schema.sync_lazy(parent_object_proxy)
+            field_node = partial.ast_nodes.first
+            result_name = field_node.alias || field_node.name
+            @response = GraphQLResultHash.new(nil, parent_object_type, parent_object_proxy, nil, false, selections, false, field_node, nil, nil)
+            @response.ordered_result_keys = [result_name]
+            @dataloader.append_job do
+              evaluate_selection(result_name, partial.ast_nodes, @response)
+            end
+          when "UNION", "INTERFACE"
+            resolved_type, _resolved_obj = resolve_type(root_type, object) # TODO lazy, errors
+            object_proxy = resolved_type.wrap(object, context)
+            object_proxy = schema.sync_lazy(object_proxy)
+            @response = GraphQLResultHash.new(nil, resolved_type, object_proxy, nil, false, selections, false, partial.ast_nodes.first, nil, nil)
+            each_gathered_selections(@response) do |selections, is_selection_array, ordered_result_keys|
+              @response.ordered_result_keys ||= ordered_result_keys
+              if is_selection_array == true
+                raise "This isn't supported yet"
+              end
+
+              @dataloader.append_job {
+                evaluate_selections(
+                  selections,
+                  @response,
+                  nil,
+                  runtime_state,
+                )
+              }
+            end
+          else
+            raise "Invariant: unsupported type kind for partial execution: #{root_type.kind.inspect} (#{root_type})"
+          end
+          nil
+        end
+
         def each_gathered_selections(response_hash)
           ordered_result_keys = []
           gathered_selections = gather_selections(response_hash.graphql_application_value, response_hash.graphql_result_type, response_hash.graphql_selections, nil, {}, ordered_result_keys)

lib/graphql/query.rb

@@ -10,6 +10,7 @@ class Query
     autoload :Context, "graphql/query/context"
     autoload :Fingerprint, "graphql/query/fingerprint"
     autoload :NullContext, "graphql/query/null_context"
+    autoload :Partial, "graphql/query/partial"
     autoload :Result, "graphql/query/result"
     autoload :Variables, "graphql/query/variables"
     autoload :InputValidationResult, "graphql/query/input_validation_result"
@@ -236,6 +237,18 @@ def operations
       with_prepared_ast { @operations }
     end
 
+    # Run subtree partials of this query and return their results.
+    # Each partial is identified with a `path:` and `object:`
+    # where the path references a field in the AST and the object will be treated
+    # as the return value from that field. Subfields of the field named by `path`
+    # will be executed with `object` as the starting point
+    # @param partials_hashes [Array<Hash{Symbol => Object}>] Hashes with `path:` and `object:` keys
+    # @return [Array<GraphQL::Query::Result>]
+    def run_partials(partials_hashes)
+      partials = partials_hashes.map { |partial_options| Partial.new(query: self, **partial_options) }
+      Execution::Interpreter.run_partials(@schema, partials, context: @context)
+    end
+
     # Get the result for this query, executing it once
     # @return [GraphQL::Query::Result] A Hash-like GraphQL response, with `"data"` and/or `"errors"` keys
     def result

lib/graphql/query/partial.rb

@@ -0,0 +1,136 @@
+# frozen_string_literal: true
+module GraphQL
+  class Query
+    # This class is _like_ a {GraphQL::Query}, except
+    # @see Query#run_partials
+    class Partial
+      def initialize(path:, object:, query:)
+        @path = path
+        @object = object
+        @query = query
+        @context = GraphQL::Query::Context.new(query: self, schema: @query.schema, values: @query.context.to_h)
+        @multiplex = nil
+        @result_values = nil
+        @result = nil
+        selections = [@query.selected_operation]
+        type = @query.schema.query # TODO could be other?
+        parent_type = nil
+        field_defn = nil
+        @path.each do |name_in_doc|
+          next_selections = []
+          selections.each do |selection|
+            selections_to_check = []
+            selections_to_check.concat(selection.selections)
+            while (sel = selections_to_check.shift)
+              case sel
+              when GraphQL::Language::Nodes::InlineFragment
+                selections_to_check.concat(sel.selections)
+              when GraphQL::Language::Nodes::FragmentSpread
+                fragment = @query.fragments[sel.name]
+                selections_to_check.concat(fragment.selections)
+              when GraphQL::Language::Nodes::Field
+                if sel.alias == name_in_doc || sel.name == name_in_doc
+                  next_selections << sel
+                end
+              else
+                raise "Unexpected selection in partial path: #{sel.class}, #{sel.inspect}"
+              end
+            end
+          end
+
+          if next_selections.empty?
+            raise ArgumentError, "Path `#{@path.inspect}` is not present in this query. `#{name_in_doc.inspect}` was not found. Try a different path or rewrite the query to include it."
+          end
+          field_name = next_selections.first.name
+          field_defn = type.get_field(field_name, @query.context) || raise("Invariant: no field called #{field_name} on #{type.graphql_name}")
+          parent_type = type
+          type = field_defn.type
+          if type.non_null?
+            type = type.of_type
+          end
+          selections = next_selections
+        end
+        @parent_type = parent_type
+        @ast_nodes = selections
+        @root_type = type
+        @field_definition = field_defn
+        @leaf = @root_type.unwrap.kind.leaf?
+      end
+
+      def leaf?
+        @leaf
+      end
+
+      attr_reader :context, :query, :ast_nodes, :root_type, :object, :field_definition, :path, :parent_type
+
+      attr_accessor :multiplex, :result_values
+
+      class Result < GraphQL::Query::Result
+        def path
+          @query.path
+        end
+
+        # @return [GraphQL::Query::Partial]
+        def partial
+          @query
+        end
+      end
+
+      def result
+        @result ||= Result.new(query: self, values: result_values)
+      end
+
+      def current_trace
+        @query.current_trace
+      end
+
+      def schema
+        @query.schema
+      end
+
+      def types
+        @query.types
+      end
+
+      # TODO dry with query
+      def after_lazy(value, &block)
+        if !defined?(@runtime_instance)
+          @runtime_instance = context.namespace(:interpreter_runtime)[:runtime]
+        end
+
+        if @runtime_instance
+          @runtime_instance.minimal_after_lazy(value, &block)
+        else
+          @schema.after_lazy(value, &block)
+        end
+      end
+
+      # TODO dry with query
+      def arguments_for(ast_node, definition, parent_object: nil)
+        arguments_cache.fetch(ast_node, definition, parent_object)
+      end
+
+      # TODO dry with query
+      def arguments_cache
+        @arguments_cache ||= Execution::Interpreter::ArgumentsCache.new(self)
+      end
+
+      # TODO dry
+      def handle_or_reraise(err)
+        @query.schema.handle_or_reraise(context, err)
+      end
+
+      def resolve_type(...)
+        @query.resolve_type(...)
+      end
+
+      def variables
+        @query.variables
+      end
+
+      def fragments
+        @query.fragments
+      end
+    end
+  end
+end