feat(Context#skip) add API for skipping fields from user code

rmosolgo · Apr 21, 2017 · f4500fd · f4500fd
1 parent e28cb0c
commit f4500fd
Show file tree

Hide file tree

Showing 3 changed files with 20 additions and 12 deletions.
diff --git a/lib/graphql/execution/execute.rb b/lib/graphql/execution/execute.rb
@@ -4,7 +4,10 @@ module Execution
     # A valid execution strategy
     # @api private
     class Execute
-      PROPAGATE_NULL = :__graphql_propagate_null__
+      # @api private
+      SKIP = Object.new
+      # @api private
+      PROPAGATE_NULL = Object.new
 
       def execute(ast_operation, root_type, query)
         result = resolve_selection(
@@ -25,14 +28,8 @@ def execute(ast_operation, root_type, query)
 
       def resolve_selection(object, current_type, selection, query_ctx, mutation: false, subscription_update: false)
         selection_result = SelectionResult.new
-        query = query_ctx.query
 
         selection.typed_children[current_type].each do |name, subselection|
-          # Can't `break` because technically multiple fields could match
-          if subscription_update && query.subscription_key != subselection.subscription_key
-            next
-          end
-
           field_result = resolve_field(
             selection_result,
             subselection,
@@ -42,6 +39,10 @@ def resolve_selection(object, current_type, selection, query_ctx, mutation: fals
             query_ctx
           )
 
+          if field_result == SKIP
+            next
+          end
+
           if mutation
             GraphQL::Execution::Lazy.resolve(field_result)
           end
@@ -145,6 +146,8 @@ def resolve_value(owner, parent_type, field_defn, field_type, value, selection,
           else
             nil
           end
+        elsif value == SKIP
+          value
         else
           case field_type.kind
           when GraphQL::TypeKinds::SCALAR

diff --git a/lib/graphql/query/context.rb b/lib/graphql/query/context.rb
@@ -71,6 +71,12 @@ def spawn(key:, selection:, parent_type:, field:)
         )
       end
 
+      # Return this value to tell the runtime
+      # to exclude this field from the response altogether
+      def skip
+        GraphQL::Execution::Execute::SKIP
+      end
+
       class FieldResolutionContext
         extend Forwardable
 
@@ -87,7 +93,8 @@ def initialize(context:, path:, selection:, field:, parent_type:)
         def_delegators :@context,
           :[], :[]=, :to_h, :key?, :fetch,
           :spawn, :query, :schema,
-          :warden, :errors, :execution_strategy, :strategy
+          :warden, :errors, :execution_strategy, :strategy,
+          :skip
 
         # @return [GraphQL::Language::Nodes::Field] The AST node for the currently-executing field
         def ast_node

diff --git a/lib/graphql/subscriptions/instrumentation.rb b/lib/graphql/subscriptions/instrumentation.rb
@@ -58,10 +58,8 @@ def call(obj, args, ctx)
             # The root object is _already_ the subscription update:
             obj
           else
-            # It should only:
-            # - Register the selection (first condition)
-            # - Pass `obj` to the child selection (second condition)
-            raise "An unselected subscription field should never be called"
+            # This is a subscription update, but this event wasn't triggered.
+            ctx.skip
           end
         end
       end