Merge pull request #1784 from rmosolgo/schema-lazy-resolve-hook

Add  a schema-level hook for lazy/batched resolution

lib/graphql/execution/execute.rb

@@ -142,11 +142,11 @@ def resolve_field(object, field_ctx)
         # If the returned object is finished, continue to coerce
         # and resolve child fields
         def continue_or_wait(raw_value, field_type, field_ctx)
-          if (lazy_method = field_ctx.schema.lazy_method_name(raw_value))
+          if field_ctx.schema.lazy?(raw_value)
             field_ctx.value = Execution::Lazy.new {
               inner_value = begin
                   begin
-                    raw_value.public_send(lazy_method)
+                    field_ctx.schema.sync_lazy(raw_value)
                   rescue GraphQL::UnauthorizedError => err
                     field_ctx.schema.unauthorized_object(err)
                   end

lib/graphql/field.rb

@@ -323,13 +323,7 @@ def build_default_resolver
 
     module DefaultLazyResolve
       def self.call(obj, args, ctx)
-        method_name = ctx.schema.lazy_method_name(obj)
-        next_obj = obj.public_send(method_name)
-        if ctx.schema.lazy?(next_obj)
-          call(next_obj, args, ctx)
-        else
-          next_obj
-        end
+        ctx.schema.sync_lazy(obj)
       end
     end
   end

lib/graphql/schema.rb

@@ -657,7 +657,7 @@ class << self
         :static_validator, :introspection_system,
         :query_analyzers, :tracers, :instrumenters,
         :query_execution_strategy, :mutation_execution_strategy, :subscription_execution_strategy,
-        :validate, :multiplex_analyzers, :lazy?, :lazy_method_name, :after_lazy,
+        :validate, :multiplex_analyzers, :lazy?, :lazy_method_name, :after_lazy, :sync_lazy,
         # Configuration
         :max_complexity=, :max_depth=,
         :metadata,
@@ -1001,9 +1001,9 @@ def resolve_type(type, obj, ctx = :__undefined__)
     # - After resolving `value`, if it's registered with `lazy_resolve` (eg, `Promise`)
     # @api private
     def after_lazy(value)
-      if (lazy_method = lazy_method_name(value))
+      if lazy?(value)
         GraphQL::Execution::Lazy.new do
-          result = value.public_send(lazy_method)
+          result = sync_lazy(value)
           # The returned result might also be lazy, so check it, too
           after_lazy(result) do |final_result|
             yield(final_result) if block_given?
@@ -1014,6 +1014,28 @@ def after_lazy(value)
       end
     end
 
+    # Override this method to handle lazy objects in a custom way.
+    # @param value [Object] an instance of a class registered with {.lazy_resolve}
+    # @param ctx [GraphQL::Query::Context] the context for this query
+    # @return [Object] A GraphQL-ready (non-lazy) object
+    def self.sync_lazy(value)
+      yield(value)
+    end
+
+    # @see Schema.sync_lazy for a hook to override
+    # @api private
+    def sync_lazy(value)
+      self.class.sync_lazy(value) { |v|
+        lazy_method = lazy_method_name(v)
+        if lazy_method
+          synced_value = value.public_send(lazy_method)
+          sync_lazy(synced_value)
+        else
+          v
+        end
+      }
+    end
+
     protected
 
     def rescues?

spec/graphql/execution/lazy_spec.rb

@@ -155,6 +155,23 @@
     end
   end
 
+  describe "Schema#sync_lazy(object)" do
+    it "Passes objects to that hook at runtime" do
+      res = run_query <<-GRAPHQL
+      {
+        a: nullableNestedSum(value: 1001) { value }
+        b: nullableNestedSum(value: 1013) { value }
+        c: nullableNestedSum(value: 1002) { value }
+      }
+      GRAPHQL
+
+      # This odd, non-adding behavior is hacked into `#sync_lazy`
+      assert_equal 101, res["data"]["a"]["value"]
+      assert_equal 113, res["data"]["b"]["value"]
+      assert_equal 102, res["data"]["c"]["value"]
+    end
+  end
+
   describe "LazyMethodMap" do
     class SubWrapper < LazyHelpers::Wrapper; end
 
@@ -165,7 +182,7 @@ class SubWrapper < LazyHelpers::Wrapper; end
       map.set(LazyHelpers::SumAll, :value)
       b = LazyHelpers::Wrapper.new(1)
       sub_b = LazyHelpers::Wrapper.new(2)
-      s = LazyHelpers::SumAll.new({}, 3)
+      s = LazyHelpers::SumAll.new(3)
       assert_equal(:item, map.get(b))
       assert_equal(:item, map.get(sub_b))
       assert_equal(:value, map.get(s))

spec/support/lazy_helpers.rb

@@ -22,7 +22,7 @@ class SumAll
     attr_reader :own_value
     attr_writer :value
 
-    def initialize(ctx, own_value)
+    def initialize(own_value)
       @own_value = own_value
       all << self
     end
@@ -56,7 +56,7 @@ def nested_sum(value:)
       if value == 13
         Wrapper.new(nil)
       else
-        SumAll.new(@context, @object + value)
+        SumAll.new(@object + value)
       end
     end
 
@@ -82,7 +82,7 @@ def nested_sum(value:)
 
     field :nestedSum, !LazySum do
       argument :value, !types.Int
-      resolve ->(o, args, c) { SumAll.new(c, args[:value]) }
+      resolve ->(o, args, c) { SumAll.new(args[:value]) }
     end
 
     field :nullableNestedSum, LazySum do
@@ -91,7 +91,7 @@ def nested_sum(value:)
         if args[:value] == 13
           Wrapper.new { raise GraphQL::ExecutionError.new("13 is unlucky") }
         else
-          SumAll.new(c, args[:value])
+          SumAll.new(args[:value])
         end
       }
     end
@@ -142,6 +142,15 @@ class LazySchema < GraphQL::Schema
     instrument(:query, SumAllInstrumentation.new(counter: nil))
     instrument(:multiplex, SumAllInstrumentation.new(counter: 1))
     instrument(:multiplex, SumAllInstrumentation.new(counter: 2))
+
+    def self.sync_lazy(lazy)
+      if lazy.is_a?(SumAll) && lazy.own_value > 1000
+        lazy.value # clear the previous set
+        lazy.own_value - 900
+      else
+        super
+      end
+    end
   end
 
   def run_query(query_str)