Autoload nested constants

Reduces require time from ~160ms to ~5ms. Autoloads all constants under
`GraphQL` to optimize boot time. Also autoloads `GraphQL::Types` and
`GraphQL::Query` because they can't be required in sequence.

Autoloads are automatically managed with `GraphQL::Autoload` similar to
`ActiveSupport::Autoload`.

guides/code_loading.md

@@ -0,0 +1,22 @@
+---
+layout: guide
+doc_stub: false
+search: true
+title: Code Loading
+section: Other
+desc: Read this before deploying GraphQL to production.
+---
+
+## Autoloading and Eager Loading
+
+GraphQL Ruby is autoloaded, which means most code won't be loaded until it is referenced. This is optimal for development and test environments where you want to boot your application as fast as possible. However, this is not optimal for production enviromnets.
+
+Production environments typically include multiple workers, and need to load an application upfront as much as possible. This ensures requests are as fast as possible at the cost of increased boot time, and forked processes don't need to load additional code. Unfortunately, there is no approach to eager code loading that is accepted by all web application frameworks.
+
+- For Rails applications, a Railtie is included that automatically eager-loads the GraphQL Ruby library for you. No action is required by the developer to opt into this behaviour.
+
+- For Sinatra applications, please put `configure(:production) { GraphQL.eager_load! }` in your application file.
+
+- For Hanami applications, please put `environment(:production) { GraphQL.eager_load! }` in your application file.
+
+- Other frameworks need to manually call `GraphQL.eager_load!` when their application is booting in production mode. If this is not done properly, GraphQL Ruby will log an warning.

lib/graphql.rb

@@ -5,8 +5,11 @@
 require "singleton"
 require "forwardable"
 require "fiber/storage"
+require "graphql/autoload"
 
 module GraphQL
+  extend Autoload
+
   class Error < StandardError
   end
 
@@ -74,53 +77,61 @@ class << self
   end
 
   self.reject_numbers_followed_by_names = false
-end
 
-# Order matters for these:
-
-require "graphql/execution_error"
-require "graphql/runtime_type_error"
-require "graphql/unresolved_type_error"
-require "graphql/invalid_null_error"
-require "graphql/analysis_error"
-require "graphql/coercion_error"
-require "graphql/invalid_name_error"
-require "graphql/integer_decoding_error"
-require "graphql/integer_encoding_error"
-require "graphql/string_encoding_error"
-require "graphql/date_encoding_error"
-require "graphql/duration_encoding_error"
-require "graphql/type_kinds"
-require "graphql/name_validator"
-require "graphql/language"
-
-require_relative "./graphql/railtie" if defined? Rails::Railtie
-
-require "graphql/analysis"
-require "graphql/tracing"
-require "graphql/dig"
-require "graphql/execution"
-require "graphql/pagination"
-require "graphql/schema"
-require "graphql/query"
-require "graphql/dataloader"
-require "graphql/types"
-require "graphql/static_validation"
-require "graphql/execution"
-require "graphql/schema/built_in_types"
-require "graphql/schema/loader"
-require "graphql/schema/printer"
-require "graphql/introspection"
-require "graphql/relay"
+  class << self
+    def ensure_eager_load!
+      if production? && !eager_loading?
+        warn "GraphQL should be eager loaded in production environments!"
+      end
+    end
+
+    private
+
+    def production?
+      (env = ENV["RACK_ENV"] || ENV["RAILS_ENV"] || ENV["HANAMI_ENV"] || ENV["APP_ENV"]) && env.to_s.downcase == "production"
+    end
+  end
+
+  autoload :ExecutionError, "graphql/execution_error"
+  autoload :RuntimeTypeError, "graphql/runtime_type_error"
+  autoload :UnresolvedTypeError, "graphql/unresolved_type_error"
+  autoload :InvalidNullError, "graphql/invalid_null_error"
+  autoload :AnalysisError, "graphql/analysis_error"
+  autoload :CoercionError, "graphql/coercion_error"
+  autoload :InvalidNameError, "graphql/invalid_name_error"
+  autoload :IntegerDecodingError, "graphql/integer_decoding_error"
+  autoload :IntegerEncodingError, "graphql/integer_encoding_error"
+  autoload :StringEncodingError, "graphql/string_encoding_error"
+  autoload :DateEncodingError, "graphql/date_encoding_error"
+  autoload :DurationEncodingError, "graphql/duration_encoding_error"
+  autoload :TypeKinds, "graphql/type_kinds"
+  autoload :NameValidator, "graphql/name_validator"
+  autoload :Language, "graphql/language"
+
+  autoload :Analysis, "graphql/analysis"
+  autoload :Tracing, "graphql/tracing"
+  autoload :Dig, "graphql/dig"
+  autoload :Execution, "graphql/execution"
+  autoload :Pagination, "graphql/pagination"
+  autoload :Schema, "graphql/schema"
+  autoload :Query, "graphql/query"
+  autoload :Dataloader, "graphql/dataloader"
+  autoload :Types, "graphql/types"
+  autoload :StaticValidation, "graphql/static_validation"
+  autoload :Execution, "graphql/execution"
+  autoload :Introspection, "graphql/introspection"
+  autoload :Relay, "graphql/relay"
+  autoload :Subscriptions, "graphql/subscriptions"
+  autoload :ParseError, "graphql/parse_error"
+  autoload :Backtrace, "graphql/backtrace"
+
+  autoload :UnauthorizedError, "graphql/unauthorized_error"
+  autoload :UnauthorizedEnumValueError, "graphql/unauthorized_enum_value_error"
+  autoload :UnauthorizedFieldError, "graphql/unauthorized_field_error"
+  autoload :LoadApplicationObjectFailedError, "graphql/load_application_object_failed_error"
+  autoload :Testing, "graphql/testing"
+  autoload :Current, "graphql/current"
+end
 
 require "graphql/version"
-require "graphql/subscriptions"
-require "graphql/parse_error"
-require "graphql/backtrace"
-
-require "graphql/unauthorized_error"
-require "graphql/unauthorized_enum_value_error"
-require "graphql/unauthorized_field_error"
-require "graphql/load_application_object_failed_error"
-require "graphql/testing"
-require "graphql/current"
+require "graphql/railtie" if defined? Rails::Railtie

lib/graphql/autoload.rb

@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+module GraphQL
+  module Autoload
+    def autoload(const_name, path)
+      @_eagerloaded_constants ||= []
+      @_eagerloaded_constants << const_name
+
+      super const_name, path
+    end
+
+    def eager_load!
+      @_eager_loading = true
+      if @_eagerloaded_constants
+        @_eagerloaded_constants.each { |const_name| const_get(const_name) }
+        @_eagerloaded_constants = nil
+      end
+    ensure
+      @_eager_loading = false
+    end
+
+    private
+
+    def eager_loading?
+      @_eager_loading ||= false
+    end
+  end
+end

lib/graphql/query.rb

@@ -1,19 +1,21 @@
 # frozen_string_literal: true
-require "graphql/query/context"
-require "graphql/query/fingerprint"
-require "graphql/query/null_context"
-require "graphql/query/result"
-require "graphql/query/variables"
-require "graphql/query/input_validation_result"
-require "graphql/query/variable_validation_error"
-require "graphql/query/validation_pipeline"
 
 module GraphQL
   # A combination of query string and {Schema} instance which can be reduced to a {#result}.
   class Query
+    extend Autoload
     include Tracing::Traceable
     extend Forwardable
 
+    autoload :Context, "graphql/query/context"
+    autoload :Fingerprint, "graphql/query/fingerprint"
+    autoload :NullContext, "graphql/query/null_context"
+    autoload :Result, "graphql/query/result"
+    autoload :Variables, "graphql/query/variables"
+    autoload :InputValidationResult, "graphql/query/input_validation_result"
+    autoload :VariableValidationError, "graphql/query/variable_validation_error"
+    autoload :ValidationPipeline, "graphql/query/validation_pipeline"
+
     class OperationNameMissingError < GraphQL::ExecutionError
       def initialize(name)
         msg = if name.nil?

lib/graphql/query/context.rb

@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-require "graphql/query/context/scoped_context"
 
 module GraphQL
   class Query
@@ -289,3 +288,5 @@ def set!(key, value)
     end
   end
 end
+
+require "graphql/query/context/scoped_context"

lib/graphql/railtie.rb

@@ -4,6 +4,7 @@ module GraphQL
   class Railtie < Rails::Railtie
     config.graphql = ActiveSupport::OrderedOptions.new
     config.graphql.parser_cache = false
+    config.eager_load_namespaces << GraphQL
 
     initializer("graphql.cache") do |app|
       if config.graphql.parser_cache

lib/graphql/schema.rb

@@ -47,6 +47,8 @@
 require "graphql/schema/subscription"
 require "graphql/schema/visibility"
 
+GraphQL.ensure_eager_load!
+
 module GraphQL
   # A GraphQL schema which may be queried with {GraphQL::Query}.
   #
@@ -1802,3 +1804,7 @@ module DefaultTraceClass
     end
   end
 end
+
+require "graphql/schema/built_in_types"
+require "graphql/schema/loader"
+require "graphql/schema/printer"

lib/graphql/schema/relay_classic_mutation.rb

@@ -1,5 +1,4 @@
 # frozen_string_literal: true
-require "graphql/types/string"
 
 module GraphQL
   class Schema

lib/graphql/types.rb

@@ -1,12 +1,19 @@
 # frozen_string_literal: true
-require "graphql/types/boolean"
-require "graphql/types/big_int"
-require "graphql/types/float"
-require "graphql/types/id"
-require "graphql/types/int"
-require "graphql/types/iso_8601_date"
-require "graphql/types/iso_8601_date_time"
-require "graphql/types/iso_8601_duration"
-require "graphql/types/json"
-require "graphql/types/string"
-require "graphql/types/relay"
+
+module GraphQL
+  module Types
+    extend Autoload
+
+    autoload :Boolean, "graphql/types/boolean"
+    autoload :BigInt, "graphql/types/big_int"
+    autoload :Float, "graphql/types/float"
+    autoload :ID, "graphql/types/id"
+    autoload :Int, "graphql/types/int"
+    autoload :JSON, "graphql/types/json"
+    autoload :String, "graphql/types/string"
+    autoload :ISO8601Date, "graphql/types/iso_8601_date"
+    autoload :ISO8601DateTime, "graphql/types/iso_8601_date_time"
+    autoload :ISO8601Duration, "graphql/types/iso_8601_duration"
+    autoload :Relay, "graphql/types/relay"
+  end
+end

spec/fixtures/eager_module/eager_class.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+module EagerModule
+  module EagerClass
+  end
+end

spec/fixtures/eager_module/other_eager_class.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+module EagerModule
+  module OtherEagerClass
+  end
+end

spec/fixtures/lazy_module/lazy_class.rb

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+module LazyModule
+  module LazyClass
+  end
+end

spec/graphql/autoload_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require "spec_helper"
+
+describe GraphQL::Autoload do
+  module LazyModule
+    extend GraphQL::Autoload
+    autoload(:LazyClass, "fixtures/lazy_module/lazy_class")
+  end
+
+  module EagerModule
+    extend GraphQL::Autoload
+    autoload(:EagerClass, "fixtures/eager_module/eager_class")
+    autoload(:OtherEagerClass, "fixtures/eager_module/other_eager_class")
+  end
+
+  describe "#autoload" do
+    it "sets autoload" do
+      assert_equal("fixtures/lazy_module/lazy_class", LazyModule.autoload?(:LazyClass))
+      LazyModule::LazyClass
+      assert_nil(LazyModule.autoload?(:LazyClass))
+    end
+  end
+
+  describe "#eager_load!" do
+    it "eagerly loads autoload entries" do
+      EagerModule.eager_load!
+
+      assert_nil(EagerModule.autoload?(:EagerClass))
+      assert_nil(EagerModule.autoload?(:OtherEagerClass))
+    end
+  end
+end

spec/graphql/types/iso_8601_date_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 require "spec_helper"
-require "graphql/types/iso_8601_date"
+
 describe GraphQL::Types::ISO8601Date do
   module DateTest
     class DateObject < GraphQL::Schema::Object

spec/graphql/types/iso_8601_date_time_spec.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 require "spec_helper"
-require "graphql/types/iso_8601_date_time"
+
 describe GraphQL::Types::ISO8601DateTime do
   module DateTimeTest
     class DateTimeObject < GraphQL::Schema::Object