[RFC] Type condition optional on inline fragments.

src/execution/execute.js

@@ -430,7 +430,11 @@ function doesFragmentConditionMatch(
   fragment: FragmentDefinition | InlineFragment,
   type: GraphQLObjectType
 ): boolean {
-  var conditionalType = typeFromAST(exeContext.schema, fragment.typeCondition);
+  var typeConditionAST = fragment.typeCondition;
+  if (!typeConditionAST) {
+    return true;
+  }
+  var conditionalType = typeFromAST(exeContext.schema, typeConditionAST);
   if (conditionalType === type) {
     return true;
   }

src/language/__tests__/kitchen-sink.graphql

@@ -17,6 +17,12 @@ query queryName($foo: ComplexType, $site: Site = MOBILE) {
         }
       }
     }
+    ... @skip(unless: $foo) {
+      id
+    }
+    ... {
+      id
+    }
   }
 }
 

src/language/__tests__/printer.js

@@ -59,6 +59,12 @@ describe('Printer', () => {
         }
       }
     }
+    ... @skip(unless: $foo) {
+      id
+    }
+    ... {
+      id
+    }
   }
 }
 

src/language/__tests__/visitor.js

@@ -321,6 +321,34 @@ describe('Visitor', () => {
       [ 'leave', 'Field', 0, undefined ],
       [ 'leave', 'SelectionSet', 'selectionSet', 'InlineFragment' ],
       [ 'leave', 'InlineFragment', 1, undefined ],
+      [ 'enter', 'InlineFragment', 2, undefined ],
+      [ 'enter', 'Directive', 0, undefined ],
+      [ 'enter', 'Name', 'name', 'Directive' ],
+      [ 'leave', 'Name', 'name', 'Directive' ],
+      [ 'enter', 'Argument', 0, undefined ],
+      [ 'enter', 'Name', 'name', 'Argument' ],
+      [ 'leave', 'Name', 'name', 'Argument' ],
+      [ 'enter', 'Variable', 'value', 'Argument' ],
+      [ 'enter', 'Name', 'name', 'Variable' ],
+      [ 'leave', 'Name', 'name', 'Variable' ],
+      [ 'leave', 'Variable', 'value', 'Argument' ],
+      [ 'leave', 'Argument', 0, undefined ],
+      [ 'leave', 'Directive', 0, undefined ],
+      [ 'enter', 'SelectionSet', 'selectionSet', 'InlineFragment' ],
+      [ 'enter', 'Field', 0, undefined ],
+      [ 'enter', 'Name', 'name', 'Field' ],
+      [ 'leave', 'Name', 'name', 'Field' ],
+      [ 'leave', 'Field', 0, undefined ],
+      [ 'leave', 'SelectionSet', 'selectionSet', 'InlineFragment' ],
+      [ 'leave', 'InlineFragment', 2, undefined ],
+      [ 'enter', 'InlineFragment', 3, undefined ],
+      [ 'enter', 'SelectionSet', 'selectionSet', 'InlineFragment' ],
+      [ 'enter', 'Field', 0, undefined ],
+      [ 'enter', 'Name', 'name', 'Field' ],
+      [ 'leave', 'Name', 'name', 'Field' ],
+      [ 'leave', 'Field', 0, undefined ],
+      [ 'leave', 'SelectionSet', 'selectionSet', 'InlineFragment' ],
+      [ 'leave', 'InlineFragment', 3, undefined ],
       [ 'leave', 'SelectionSet', 'selectionSet', 'Field' ],
       [ 'leave', 'Field', 0, undefined ],
       [ 'leave', 'SelectionSet', 'selectionSet', 'OperationDefinition' ],

src/language/ast.js

@@ -142,7 +142,7 @@ export type FragmentSpread = {
 export type InlineFragment = {
   kind: 'InlineFragment';
   loc?: ?Location;
-  typeCondition: NamedType;
+  typeCondition?: ?NamedType;
   directives?: ?Array<Directive>;
   selectionSet: SelectionSet;
 }

src/language/parser.js

@@ -377,25 +377,29 @@ function parseArgument(parser): Argument {
  *
  * FragmentSpread : ... FragmentName Directives?
  *
- * InlineFragment : ... on TypeCondition Directives? SelectionSet
+ * InlineFragment : ... TypeCondition? Directives? SelectionSet
  */
 function parseFragment(parser): FragmentSpread | InlineFragment {
   var start = parser.token.start;
   expect(parser, TokenKind.SPREAD);
-  if (parser.token.value === 'on') {
-    advance(parser);
+  if (peek(parser, TokenKind.NAME) && parser.token.value !== 'on') {
     return {
-      kind: INLINE_FRAGMENT,
-      typeCondition: parseNamedType(parser),
+      kind: FRAGMENT_SPREAD,
+      name: parseFragmentName(parser),
       directives: parseDirectives(parser),
-      selectionSet: parseSelectionSet(parser),
       loc: loc(parser, start)
     };
   }
+  var typeCondition = null;
+  if (parser.token.value === 'on') {
+    advance(parser);
+    typeCondition = parseNamedType(parser);
+  }
   return {
-    kind: FRAGMENT_SPREAD,
-    name: parseFragmentName(parser),
+    kind: INLINE_FRAGMENT,
+    typeCondition,
     directives: parseDirectives(parser),
+    selectionSet: parseSelectionSet(parser),
     loc: loc(parser, start)
   };
 }

src/language/printer.js

@@ -55,9 +55,12 @@ var printDocASTReducer = {
     '...' + name + wrap(' ', join(directives, ' ')),
 
   InlineFragment: ({ typeCondition, directives, selectionSet }) =>
-    `... on ${typeCondition} ` +
-    wrap('', join(directives, ' '), ' ') +
-    selectionSet,
+    join([
+      '...',
+      wrap('on ', typeCondition),
+      join(directives, ' '),
+      selectionSet
+    ], ' '),
 
   FragmentDefinition: ({ name, typeCondition, directives, selectionSet }) =>
     `fragment ${name} on ${typeCondition} ` +

src/utilities/TypeInfo.js

@@ -132,7 +132,10 @@ export class TypeInfo {
         break;
       case Kind.INLINE_FRAGMENT:
       case Kind.FRAGMENT_DEFINITION:
-        type = typeFromAST(schema, node.typeCondition);
+        var typeConditionAST = node.typeCondition;
+        type = typeConditionAST ?
+          typeFromAST(schema, typeConditionAST) :
+          this.getType();
         this._typeStack.push(type);
         break;
       case Kind.VARIABLE_DEFINITION:

src/validation/__tests__/FieldsOnCorrectType.js

@@ -185,6 +185,9 @@ describe('Validate: Fields on correct type', () => {
         ... on Dog {
           name
         }
+        ... {
+          name
+        }
       }
     `);
   });

src/validation/__tests__/KnownFragmentNames.js

@@ -32,6 +32,9 @@ describe('Validate: Known fragment names', () => {
           ... on Human {
             ...HumanFields2
           }
+          ... {
+            name
+          }
         }
       }
       fragment HumanFields1 on Human {

src/validation/__tests__/KnownTypeNames.js

@@ -28,7 +28,7 @@ describe('Validate: Known type names', () => {
     expectPassesRule(KnownTypeNames, `
       query Foo($var: String, $required: [String!]!) {
         user(id: 4) {
-          pets { ... on Pet { name }, ...PetFields }
+          pets { ... on Pet { name }, ...PetFields, ... { name } }
         }
       }
       fragment PetFields on Pet {