Merge pull request #698 from graphql/type-info-safe

Fix: Type safety for TypeInfo.

Author: leebyron

src/utilities/TypeInfo.js

@@ -11,6 +11,8 @@
 import * as Kind from '../language/kinds';
 import {
   isCompositeType,
+  isInputType,
+  isOutputType,
   getNullableType,
   getNamedType,
   GraphQLObjectType,
@@ -117,12 +119,11 @@ export class TypeInfo {
     switch (node.kind) {
       case Kind.SELECTION_SET:
         const namedType = getNamedType(this.getType());
-        let compositeType: ?GraphQLCompositeType;
-        if (isCompositeType(namedType)) {
-          // isCompositeType is a type refining predicate, so this is safe.
-          compositeType = ((namedType: any): GraphQLCompositeType);
-        }
-        this._parentTypeStack.push(compositeType);
+        this._parentTypeStack.push(
+          isCompositeType(namedType) ?
+            ((namedType: any): GraphQLCompositeType) :
+            undefined
+        );
         break;
       case Kind.FIELD:
         const parentType = this.getParentType();
@@ -153,11 +154,19 @@ export class TypeInfo {
         const outputType = typeConditionAST ?
           typeFromAST(schema, typeConditionAST) :
           this.getType();
-        this._typeStack.push(((outputType: any): GraphQLOutputType));
+        this._typeStack.push(
+          isOutputType(outputType) ?
+            ((outputType: any): GraphQLOutputType) :
+            undefined
+        );
         break;
       case Kind.VARIABLE_DEFINITION:
         const inputType = typeFromAST(schema, node.type);
-        this._inputTypeStack.push(((inputType: any): GraphQLInputType));
+        this._inputTypeStack.push(
+          isInputType(inputType) ?
+            ((inputType: any): GraphQLInputType) :
+            undefined
+        );
         break;
       case Kind.ARGUMENT:
         let argDef;

src/validation/rules/FragmentsOnCompositeTypes.js

@@ -13,6 +13,7 @@ import { GraphQLError } from '../../error';
 import { print } from '../../language/printer';
 import { isCompositeType } from '../../type/definition';
 import type { GraphQLType } from '../../type/definition';
+import { typeFromAST } from '../../utilities/typeFromAST';
 
 
 export function inlineFragmentOnNonCompositeErrorMessage(
@@ -39,16 +40,18 @@ export function fragmentOnNonCompositeErrorMessage(
 export function FragmentsOnCompositeTypes(context: ValidationContext): any {
   return {
     InlineFragment(node) {
-      const type = context.getType();
-      if (node.typeCondition && type && !isCompositeType(type)) {
-        context.reportError(new GraphQLError(
-          inlineFragmentOnNonCompositeErrorMessage(print(node.typeCondition)),
-          [ node.typeCondition ]
-        ));
+      if (node.typeCondition) {
+        const type = typeFromAST(context.getSchema(), node.typeCondition);
+        if (type && !isCompositeType(type)) {
+          context.reportError(new GraphQLError(
+            inlineFragmentOnNonCompositeErrorMessage(print(node.typeCondition)),
+            [ node.typeCondition ]
+          ));
+        }
       }
     },
     FragmentDefinition(node) {
-      const type = context.getType();
+      const type = typeFromAST(context.getSchema(), node.typeCondition);
       if (type && !isCompositeType(type)) {
         context.reportError(new GraphQLError(
           fragmentOnNonCompositeErrorMessage(