add runtime hook for breadth execution patterns.

Author: gmac

lib/graphql/execution/interpreter/runtime.rb

@@ -472,6 +472,7 @@ def evaluate_selection_with_resolved_keyword_args(kwarg_arguments, resolved_argu
             end
             @current_trace.end_execute_field(field_defn, object, kwarg_arguments, query, app_result)
             after_lazy(app_result, field: field_defn, ast_node: ast_node, owner_object: object, arguments: resolved_arguments, result_name: result_name, result: selection_result, runtime_state: runtime_state) do |inner_result, runtime_state|
+              next if exit_with_inner_result?(inner_result, result_name, selection_result)
               owner_type = selection_result.graphql_result_type
               return_type = field_defn.type
               continue_value = continue_value(inner_result, field_defn, return_type.non_null?, ast_node, result_name, selection_result)
@@ -492,6 +493,11 @@ def evaluate_selection_with_resolved_keyword_args(kwarg_arguments, resolved_argu
           end
         end
 
+        # Hook for breadth-first implementations to exit after a single resolver generation.
+        def exit_with_inner_result?(inner_result, result_name, selection_result)
+          false
+        end
+
         def set_result(selection_result, result_name, value, is_child_result, is_non_null)
           if !selection_result.graphql_dead
             if value.nil? && is_non_null

spec/graphql/execution/breadth_runtime_spec.rb

@@ -0,0 +1,325 @@
+# frozen_string_literal: true
+require "spec_helper"
+
+describe "GraphQL::Execution::Interpreter for breadth-first execution" do
+  # A breadth-first interpreter uses the following runtime interface:
+  # - evaluate_selection(result_key, ast_nodes, selections_result)
+  # - exit_with_inner_result?
+  class SimpleBreadthRuntime < GraphQL::Execution::Interpreter::Runtime
+    class BreadthObject < GraphQL::Execution::Interpreter::Runtime::GraphQLResultHash
+      attr_accessor :breadth_index
+    end
+
+    def initialize(query:)
+      query.multiplex = GraphQL::Execution::Multiplex.new(
+        schema: query.schema,
+        queries: [query],
+        context: query.context,
+        max_complexity: nil,
+      )
+
+      super(query: query, lazies_at_depth: Hash.new { |h, k| h[k] = [] })
+      @breadth_results_by_key = {}
+    end
+
+    def run
+      result = nil
+      query.current_trace.execute_multiplex(multiplex: query.multiplex) do
+        query.current_trace.execute_query(query: query) do
+          result = yield
+        end
+      end
+      result
+    ensure
+      delete_all_interpreter_context
+    end
+
+    def evaluate_breadth_selection(objects, parent_type, node)
+      result_key = node.alias || node.name
+      @breadth_results_by_key[result_key] = Array.new(objects.size)
+      objects.each_with_index do |object, index|
+        app_value = parent_type.wrap(object, query.context)
+        breadth_object = BreadthObject.new(nil, parent_type, app_value, nil, false, node.selections, false, node, nil, nil)
+        breadth_object.ordered_result_keys = []
+        breadth_object.breadth_index = index
+
+        state = get_current_runtime_state
+        state.current_result_name = nil
+        state.current_result = breadth_object
+        @dataloader.append_job { evaluate_selection(result_key, node, breadth_object) }
+      end
+
+      @dataloader.run
+      GraphQL::Execution::Interpreter::Resolve.resolve_each_depth(@lazies_at_depth, @dataloader)
+
+      @breadth_results_by_key[result_key]
+    end
+
+    def exit_with_inner_result?(inner_result, result_key, breadth_object)
+      @breadth_results_by_key[result_key][breadth_object.breadth_index] = inner_result
+      true
+    end
+  end
+
+  class PassthroughLoader < GraphQL::Batch::Loader
+    def perform(objects)
+      objects.each { |obj| fulfill(obj, obj) }
+    end
+  end
+
+  class SimpleHashBatchLoader < GraphQL::Batch::Loader
+    def initialize(key)
+      super()
+      @key = key
+    end
+
+    def perform(objects)
+      objects.each { |obj| fulfill(obj, obj.fetch(@key)) }
+    end
+  end
+
+  class UpcaseExtension < GraphQL::Schema::FieldExtension
+    def after_resolve(value:, **rest)
+      value&.upcase
+    end
+  end
+
+  class RangeInput < GraphQL::Schema::InputObject
+    argument :min, Int
+    argument :max, Int
+
+    def prepare
+      min..max
+    end
+  end
+
+  class BaseField < GraphQL::Schema::Field
+    def authorized?(obj, args, ctx)
+      if !ctx[:field_auth].nil?
+        ctx[:field_auth]
+      elsif !ctx[:lazy_field_auth].nil?
+        PassthroughLoader.load(ctx[:lazy_field_auth])
+      elsif !ctx[:field_auth_with_error].nil?
+        raise GraphQL::ExecutionError, "Not authorized" unless ctx[:field_auth_with_error]
+      else
+        true
+      end
+    end
+  end
+
+  class BaseObject < GraphQL::Schema::Object
+    field_class BaseField
+  end
+
+  class Query < BaseObject
+    field :foo, String
+
+    def foo
+      object[:foo]
+    end
+
+    field :lazy_foo, String
+
+    def lazy_foo
+      SimpleHashBatchLoader.for(:foo).load(object)
+    end
+
+    field :maybe_lazy_foo, String
+
+    def maybe_lazy_foo
+      if object[:foo] == "beep"
+        SimpleHashBatchLoader.for(:foo).load(object)
+      else
+        object[:foo]
+      end
+    end
+
+    field :nested_lazy_foo, String
+
+    def nested_lazy_foo
+      PassthroughLoader
+        .load(object)
+        .then { |obj| SimpleHashBatchLoader.for(:foo).load(obj) }
+        .then { |str| str }
+    end
+
+    field :upcase_foo, String, extensions: [UpcaseExtension]
+
+    def upcase_foo
+      object[:foo]
+    end
+
+    field :lazy_upcase_foo, String, extensions: [UpcaseExtension]
+
+    def lazy_upcase_foo
+      SimpleHashBatchLoader.for(:foo).load(object)
+    end
+
+    field :go_boom, String
+
+    def go_boom
+      raise GraphQL::ExecutionError, "boom"
+    end
+
+    field :args, String do |f|
+      f.argument :a, String
+      f.argument :b, String
+    end
+
+    def args(a:, b:)
+      "#{a}#{b}"
+    end
+
+    field :range, String do |f|
+      f.argument :input, RangeInput
+    end
+
+    def range(input:)
+      "#{input.min}-#{input.max}"
+    end
+
+    field :extras, String, extras: [:lookahead]
+
+    def extras(lookahead:)
+      lookahead.field.name
+    end
+
+    # uses default resolver...
+    field :fizz, String
+  end
+
+  class TestSchema < GraphQL::Schema
+    use(GraphQL::Batch)
+    query Query
+  end
+
+  SCHEMA_FROM_DEF = GraphQL::Schema.from_definition(
+    %|type Query { a: String }|,
+    default_resolve: {
+      "Query" => { "a" => ->(obj, _args, _ctx) { obj["a"] } },
+    },
+  )
+
+  OBJECTS = [{ foo: "fizz" }, { foo: "buzz" }, { foo: "beep" }, { foo: "boom" }].freeze
+  EXPECTED_RESULTS = ["fizz", "buzz", "beep", "boom"].freeze
+
+  def test_maps_sync_results
+    result = map_breadth_objects(OBJECTS, "{ foo }")
+    assert_equal EXPECTED_RESULTS, result
+  end
+
+  def test_maps_lazy_results
+    result = map_breadth_objects(OBJECTS, "{ lazyFoo }")
+    assert_equal EXPECTED_RESULTS, result
+  end
+
+  def test_maps_sometimes_lazy_results
+    result = map_breadth_objects(OBJECTS, "{ maybeLazyFoo }")
+    assert_equal EXPECTED_RESULTS, result
+  end
+
+  def test_maps_nested_lazy_results
+    result = map_breadth_objects(OBJECTS, "{ nestedLazyFoo }")
+    assert_equal EXPECTED_RESULTS, result
+  end
+
+  def test_maps_field_extension_results
+    result = map_breadth_objects(OBJECTS, "{ upcaseFoo }")
+    assert_equal ["FIZZ", "BUZZ", "BEEP", "BOOM"], result
+  end
+
+  def test_maps_lazy_field_extension_results
+    result = map_breadth_objects(OBJECTS, "{ lazyUpcaseFoo }")
+    assert_equal ["FIZZ", "BUZZ", "BEEP", "BOOM"], result
+  end
+
+  def test_maps_fields_with_authorization
+    context = { field_auth: false }
+    result = map_breadth_objects(OBJECTS, "{ foo }", context: context)
+    assert_equal [nil, nil, nil, nil], result
+  end
+
+  def test_maps_fields_with_lazy_authorization
+    context = { lazy_field_auth: false }
+    result = map_breadth_objects(OBJECTS, "{ foo }", context: context)
+    assert result.all? { |r| r.is_a?(GraphQL::UnauthorizedFieldError) }
+  end
+
+  def test_maps_fields_with_authorization_errors
+    context = { field_auth_with_error: false }
+    result = map_breadth_objects(OBJECTS, "{ foo }", context: context)
+    assert result.all? { |r| r.is_a?(GraphQL::ExecutionError) }
+  end
+
+  def test_maps_field_errors
+    result = map_breadth_objects(OBJECTS, "{ goBoom }")
+    assert result.all? { |r| r.is_a?(GraphQL::ExecutionError) }
+    assert_equal ["boom", "boom", "boom", "boom"], result.map(&:message)
+  end
+
+  def test_maps_basic_arguments
+    doc = %|{ args(a:"fizz", b:"buzz") }|
+    result = map_breadth_objects([{}], doc)
+    assert_equal ["fizzbuzz"], result
+  end
+
+  def test_maps_basic_arguments_with_variables
+    doc = %|query($b: String) { args(a:"fizz", b: $b) }|
+    result = map_breadth_objects([{}], doc, variables: { b: "buzz" })
+    assert_equal ["fizzbuzz"], result
+  end
+
+  def test_maps_prepared_input_object
+    doc = %|{ range(input: { min: 1, max: 2 }) }|
+    result = map_breadth_objects([{}], doc)
+    assert_equal ["1-2"], result
+  end
+
+  def test_maps_prepared_input_object_with_variables
+    doc = %|query($b: Int) { range(input: { min: 1, max: $b }) }|
+    result = map_breadth_objects([{}], doc, variables: { b: 2 })
+    assert_equal ["1-2"], result
+  end
+
+  def test_maps_extras_arguments
+    result = map_breadth_objects([{}], "{ extras }")
+    assert_equal ["extras"], result
+  end
+
+  def test_uses_default_resolver_for_hash_keys
+    result = map_breadth_objects([{ fizz: "buzz" }], "{ fizz }")
+    assert_equal ["buzz"], result
+  end
+
+  def test_uses_default_resolver_for_method_calls
+    entity = Struct.new(:fizz)
+    result = map_breadth_objects([entity.new("buzz")], "{ fizz }")
+    assert_equal ["buzz"], result
+  end
+
+  def test_maps_schemas_from_definition
+    objects = [{ "a" => "1" }, { "a" => "2" }]
+    result = map_breadth_objects(objects, "{ a }", schema: SCHEMA_FROM_DEF)
+    assert_equal ["1", "2"], result
+  end
+
+  def test_maps_results_with_multiple_nodes
+    result = map_breadth_objects(OBJECTS, "{ foo foo }")
+    assert_equal EXPECTED_RESULTS, result
+  end
+
+  private
+
+  def map_breadth_objects(objects, doc, schema: TestSchema, variables: {}, context: {})
+    query = GraphQL::Query.new(
+      schema,
+      document: GraphQL.parse(doc),
+      variables: variables,
+      context: context,
+    )
+
+    node = query.document.definitions.first.selections.first
+    runtime = SimpleBreadthRuntime.new(query: query)
+    runtime.run { runtime.evaluate_breadth_selection(objects, schema.query, node) }
+  end
+end