Add flag for parser

src/__testUtils__/kitchenSinkQuery.ts

@@ -10,7 +10,7 @@ query queryName($foo: ComplexType, $site: Site = MOBILE) @onQuery {
           ...frag @onFragmentSpread
         }
       }
-      
+
       field3!
       field4?
       requiredField5: field5!

src/execution/__tests__/variables-test.ts

@@ -160,7 +160,7 @@ function executeQuery(
   query: string,
   variableValues?: { [variable: string]: unknown },
 ) {
-  const document = parse(query);
+  const document = parse(query, { experimentalFragmentArguments: true });
   return executeSync({ schema, document, variableValues });
 }
 

src/language/__tests__/parser-test.ts

@@ -607,16 +607,32 @@ describe('Parser', () => {
     expect('loc' in result).to.equal(false);
   });
 
-  it('allows parsing fragment defined arguments', () => {
+  it('allows parsing fragment defined variables', () => {
     const document = 'fragment a($v: Boolean = false) on t { f(v: $v) }';
 
-    expect(() => parse(document)).to.not.throw();
+    expect(() =>
+      parse(document, { experimentalFragmentArguments: true }),
+    ).to.not.throw();
+  });
+
+  it('disallows parsing fragment defined variables without experimental flag', () => {
+    const document = 'fragment a($v: Boolean = false) on t { f(v: $v) }';
+
+    expect(() => parse(document)).to.throw();
   });
 
   it('allows parsing fragment spread arguments', () => {
     const document = 'fragment a on t { ...b(v: $v) }';
 
-    expect(() => parse(document)).to.not.throw();
+    expect(() =>
+      parse(document, { experimentalFragmentArguments: true }),
+    ).to.not.throw();
+  });
+
+  it('disallows parsing fragment spread arguments without experimental flag', () => {
+    const document = 'fragment a on t { ...b(v: $v) }';
+
+    expect(() => parse(document)).to.throw();
   });
 
   it('contains location that can be Object.toStringified, JSON.stringified, or jsutils.inspected', () => {

src/language/__tests__/printer-test.ts

@@ -113,6 +113,7 @@ describe('Printer: Query document', () => {
   it('prints fragment with argument definition directives', () => {
     const fragmentWithArgumentDefinitionDirective = parse(
       'fragment Foo($foo: TestType @test) on TestType @testDirective { id }',
+      { experimentalFragmentArguments: true },
     );
     expect(print(fragmentWithArgumentDefinitionDirective)).to.equal(dedent`
       fragment Foo($foo: TestType @test) on TestType @testDirective {
@@ -128,6 +129,7 @@ describe('Printer: Query document', () => {
           id
         }
       `,
+      { experimentalFragmentArguments: true },
     );
     expect(print(fragmentWithArgumentDefinition)).to.equal(dedent`
       fragment Foo($a: ComplexType, $b: Boolean = false) on TestType {
@@ -139,6 +141,7 @@ describe('Printer: Query document', () => {
   it('prints fragment spread with arguments', () => {
     const fragmentSpreadWithArguments = parse(
       'fragment Foo on TestType { ...Bar(a: {x: $x}, b: true) }',
+      { experimentalFragmentArguments: true },
     );
     expect(print(fragmentSpreadWithArguments)).to.equal(dedent`
       fragment Foo on TestType {
@@ -150,6 +153,7 @@ describe('Printer: Query document', () => {
   it('prints fragment spread with multi-line arguments', () => {
     const fragmentSpreadWithArguments = parse(
       'fragment Foo on TestType { ...Bar(a: {x: $x, y: $y, z: $z, xy: $xy}, b: true, c: "a long string extending arguments over max length") }',
+      { experimentalFragmentArguments: true },
     );
     expect(print(fragmentSpreadWithArguments)).to.equal(dedent`
       fragment Foo on TestType {

src/language/__tests__/visitor-test.ts

@@ -458,6 +458,7 @@ describe('Visitor', () => {
   it('visits arguments defined on fragments', () => {
     const ast = parse('fragment a($v: Boolean = false) on t { f }', {
       noLocation: true,
+      experimentalFragmentArguments: true,
     });
     const visited: Array<any> = [];
 
@@ -507,6 +508,7 @@ describe('Visitor', () => {
   it('visits arguments on fragment spreads', () => {
     const ast = parse('fragment a on t { ...s(v: false) }', {
       noLocation: true,
+      experimentalFragmentArguments: true,
     });
     const visited: Array<any> = [];
 

src/language/parser.ts

@@ -91,6 +91,27 @@ export interface ParseOptions {
    */
   maxTokens?: number | undefined;
 
+  /**
+   * EXPERIMENTAL:
+   *
+   * If enabled, the parser will understand and parse fragment variable definitions
+   * and arguments on fragment spreads. Fragment variable definitions will be represented
+   * in the `variableDefinitions` field of the FragmentDefinitionNode.
+   * Fragment spread arguments will be represented in the `arguments` field of FragmentSpreadNode.
+   *
+   *  For example:
+   *
+   * ```graphql
+   * {
+   *   t { ...A(var: true) }
+   * }
+   * fragment A($var: Boolean = false) on T {
+   *   ...B(x: $var)
+   * }
+   * ```
+   */
+  experimentalFragmentArguments?: boolean | undefined;
+
   /**
    * EXPERIMENTAL:
    *
@@ -544,7 +565,10 @@ export class Parser {
     const hasTypeCondition = this.expectOptionalKeyword('on');
     if (!hasTypeCondition && this.peek(TokenKind.NAME)) {
       const name = this.parseFragmentName();
-      if (this.peek(TokenKind.PAREN_L)) {
+      if (
+        this.peek(TokenKind.PAREN_L) &&
+        this._options.experimentalFragmentArguments
+      ) {
         return this.node<FragmentSpreadNode>(start, {
           kind: Kind.FRAGMENT_SPREAD,
           name,
@@ -578,7 +602,9 @@ export class Parser {
     return this.node<FragmentDefinitionNode>(start, {
       kind: Kind.FRAGMENT_DEFINITION,
       name: this.parseFragmentName(),
-      variableDefinitions: this.parseVariableDefinitions(),
+      variableDefinitions: this._options.experimentalFragmentArguments
+        ? this.parseVariableDefinitions()
+        : undefined,
       typeCondition: (this.expectKeyword('on'), this.parseNamedType()),
       directives: this.parseDirectives(false),
       selectionSet: this.parseSelectionSet(),

src/utilities/__tests__/TypeInfo-test.ts

@@ -519,7 +519,8 @@ describe('visitWithTypeInfo', () => {
   it('supports traversals of fragment arguments', () => {
     const typeInfo = new TypeInfo(testSchema);
 
-    const ast = parse(`
+    const ast = parse(
+      `
       query {
         ...Foo(x: 4)
       }
@@ -529,7 +530,9 @@ describe('visitWithTypeInfo', () => {
       ) on QueryRoot {
         human(id: $x) { name }
       }
-    `);
+    `,
+      { experimentalFragmentArguments: true },
+    );
 
     const visited: Array<any> = [];
     visit(

src/validation/__tests__/harness.ts

@@ -123,7 +123,7 @@ export function expectValidationErrorsWithSchema(
   rule: ValidationRule,
   queryStr: string,
 ): any {
-  const doc = parse(queryStr);
+  const doc = parse(queryStr, { experimentalFragmentArguments: true });
   const errors = validate(schema, doc, [rule]);
   return expectJSON(errors);
 }