Re-apply changes, address olds comments, but do not start on function…

…al work

src/execution/__tests__/variables-test.ts

@@ -1006,6 +1006,156 @@ describe('Execute: Handles inputs', () => {
     });
   });
 
+  describe('using fragment arguments', () => {
+    it('when there are no fragment arguments', () => {
+      const result = executeQuery(`
+        query {
+          ...a
+        }
+        fragment a on TestType {
+          fieldWithNonNullableStringInput(input: "A")
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNonNullableStringInput: '"A"',
+        },
+      });
+    });
+
+    it('when a value is required and provided', () => {
+      const result = executeQuery(`
+        query {
+          ...a(value: "A")
+        }
+        fragment a($value: String!) on TestType {
+          fieldWithNonNullableStringInput(input: $value)
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNonNullableStringInput: '"A"',
+        },
+      });
+    });
+
+    it('when a value is required and not provided', () => {
+      const result = executeQuery(`
+        query {
+          ...a
+        }
+        fragment a($value: String!) on TestType {
+          fieldWithNullableStringInput(input: $value)
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNullableStringInput: null,
+        },
+      });
+    });
+
+    it('when the definition has a default and is provided', () => {
+      const result = executeQuery(`
+        query {
+          ...a(value: "A")
+        }
+        fragment a($value: String! = "B") on TestType {
+          fieldWithNonNullableStringInput(input: $value)
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNonNullableStringInput: '"A"',
+        },
+      });
+    });
+
+    it('when the definition has a default and is not provided', () => {
+      const result = executeQuery(`
+        query {
+          ...a
+        }
+        fragment a($value: String! = "B") on TestType {
+          fieldWithNonNullableStringInput(input: $value)
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNonNullableStringInput: '"B"',
+        },
+      });
+    });
+
+    it('when the definition has a non-nullable default and is provided null', () => {
+      const result = executeQuery(`
+        query {
+          ...a(value: null)
+        }
+        fragment a($value: String! = "B") on TestType {
+          fieldWithNullableStringInput(input: $value)
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNullableStringInput: 'null',
+        },
+      });
+    });
+
+    it('when the definition has no default and is not provided', () => {
+      const result = executeQuery(`
+        query {
+          ...a
+        }
+        fragment a($value: String) on TestType {
+          fieldWithNonNullableStringInputAndDefaultArgumentValue(input: $value)
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          fieldWithNonNullableStringInputAndDefaultArgumentValue:
+            '"Hello World"',
+        },
+      });
+    });
+
+    it('when the argument variable is nested in a complex type', () => {
+      const result = executeQuery(`
+        query {
+          ...a(value: "C")
+        }
+        fragment a($value: String) on TestType {
+          list(input: ["A", "B", $value, "D"])
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          list: '["A", "B", "C", "D"]',
+        },
+      });
+    });
+
+    it('when argument variables are used recursively', () => {
+      const result = executeQuery(`
+        query {
+          ...a(aValue: "C")
+        }
+        fragment a($aValue: String) on TestType {
+          ...b(bValue: $aValue)
+        }
+        fragment b($bValue: String) on TestType {
+          list(input: ["A", "B", $bValue, "D"])
+        }
+      `);
+      expect(result).to.deep.equal({
+        data: {
+          list: '["A", "B", "C", "D"]',
+        },
+      });
+    });
+  });
+
   describe('getVariableValues: limit maximum number of coercion errors', () => {
     const doc = parse(`
       query ($input: [String!]) {

src/execution/collectFields.ts

@@ -2,13 +2,17 @@ import { AccumulatorMap } from '../jsutils/AccumulatorMap';
 import type { ObjMap } from '../jsutils/ObjMap';
 
 import type {
+  ArgumentNode,
   FieldNode,
   FragmentDefinitionNode,
   FragmentSpreadNode,
   InlineFragmentNode,
   SelectionSetNode,
+  ValueNode,
+  VariableDefinitionNode,
 } from '../language/ast';
 import { Kind } from '../language/kinds';
+import { visit } from '../language/visitor';
 
 import type { GraphQLObjectType } from '../type/definition';
 import { isAbstractType } from '../type/definition';
@@ -139,12 +143,18 @@ function collectFieldsImpl(
         ) {
           continue;
         }
+        const selectionSetWithAppliedArguments =
+          selectionSetWithFragmentArgumentsApplied(
+            fragment.argumentDefinitions,
+            selection.arguments,
+            fragment.selectionSet,
+          );
         collectFieldsImpl(
           schema,
           fragments,
           variableValues,
           runtimeType,
-          fragment.selectionSet,
+          selectionSetWithAppliedArguments,
           fields,
           visitedFragmentNames,
         );
@@ -154,6 +164,41 @@ function collectFieldsImpl(
   }
 }
 
+function selectionSetWithFragmentArgumentsApplied(
+  argumentDefinitions: Readonly<Array<VariableDefinitionNode>> | undefined,
+  fragmentArguments: Readonly<Array<ArgumentNode>> | undefined,
+  selectionSet: SelectionSetNode,
+): SelectionSetNode {
+  const providedArguments = new Map<string, ArgumentNode>();
+  if (fragmentArguments) {
+    for (const argument of fragmentArguments) {
+      providedArguments.set(argument.name.value, argument);
+    }
+  }
+
+  const fragmentArgumentValues = new Map<string, ValueNode>();
+  if (argumentDefinitions) {
+    for (const argumentDef of argumentDefinitions) {
+      const variableName = argumentDef.variable.name.value;
+      const providedArg = providedArguments.get(variableName);
+      if (providedArg) {
+        // Not valid if the providedArg is null and argumentDef is non-null
+        fragmentArgumentValues.set(variableName, providedArg.value);
+      } else if (argumentDef.defaultValue) {
+        fragmentArgumentValues.set(variableName, argumentDef.defaultValue);
+      }
+      // If argumentDef is non-null, expect a provided arg or non-null default value.
+      // Otherwise just preserve the variable as-is: it will be treated as unset by the executor.
+    }
+  }
+
+  return visit(selectionSet, {
+    Variable(node) {
+      return fragmentArgumentValues.get(node.name.value);
+    },
+  });
+}
+
 /**
  * Determines if a field should be included based on the `@include` and `@skip`
  * directives, where `@skip` has higher precedence than `@include`.

src/language/__tests__/parser-test.ts

@@ -591,13 +591,16 @@ describe('Parser', () => {
     expect('loc' in result).to.equal(false);
   });
 
-  it('Legacy: allows parsing fragment defined variables', () => {
+  it('allows parsing fragment defined arguments', () => {
     const document = 'fragment a($v: Boolean = false) on t { f(v: $v) }';
 
-    expect(() =>
-      parse(document, { allowLegacyFragmentVariables: true }),
-    ).to.not.throw();
-    expect(() => parse(document)).to.throw('Syntax Error');
+    expect(() => parse(document)).to.not.throw();
+  });
+
+  it('allows parsing fragment spread arguments', () => {
+    const document = 'fragment a on t { ...b(v: $v) }';
+
+    expect(() => parse(document)).to.not.throw();
   });
 
   it('contains location that can be Object.toStringified, JSON.stringified, or jsutils.inspected', () => {

src/language/__tests__/printer-test.ts

@@ -110,34 +110,58 @@ describe('Printer: Query document', () => {
     `);
   });
 
-  it('Legacy: prints fragment with variable directives', () => {
-    const queryASTWithVariableDirective = parse(
+  it('prints fragment with argument definition directives', () => {
+    const fragmentWithArgumentDefinitionDirective = parse(
       'fragment Foo($foo: TestType @test) on TestType @testDirective { id }',
-      { allowLegacyFragmentVariables: true },
     );
-    expect(print(queryASTWithVariableDirective)).to.equal(dedent`
+    expect(print(fragmentWithArgumentDefinitionDirective)).to.equal(dedent`
       fragment Foo($foo: TestType @test) on TestType @testDirective {
         id
       }
     `);
   });
 
-  it('Legacy: correctly prints fragment defined variables', () => {
-    const fragmentWithVariable = parse(
+  it('correctly prints fragment defined arguments', () => {
+    const fragmentWithArgumentDefinition = parse(
       `
         fragment Foo($a: ComplexType, $b: Boolean = false) on TestType {
           id
         }
       `,
-      { allowLegacyFragmentVariables: true },
     );
-    expect(print(fragmentWithVariable)).to.equal(dedent`
+    expect(print(fragmentWithArgumentDefinition)).to.equal(dedent`
       fragment Foo($a: ComplexType, $b: Boolean = false) on TestType {
         id
       }
     `);
   });
 
+  it('prints fragment spread with arguments', () => {
+    const fragmentSpreadWithArguments = parse(
+      'fragment Foo on TestType { ...Bar(a: {x: $x}, b: true) }',
+    );
+    expect(print(fragmentSpreadWithArguments)).to.equal(dedent`
+      fragment Foo on TestType {
+        ...Bar(a: { x: $x }, b: true)
+      }
+    `);
+  });
+
+  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") }',
+    );
+    expect(print(fragmentSpreadWithArguments)).to.equal(dedent`
+      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"
+        )
+      }
+    `);
+  });
+
   it('prints kitchen sink without altering ast', () => {
     const ast = parse(kitchenSinkQuery, {
       noLocation: true,

src/language/__tests__/visitor-test.ts

@@ -455,10 +455,9 @@ describe('Visitor', () => {
     ]);
   });
 
-  it('Legacy: visits variables defined in fragments', () => {
+  it('visits arguments defined on fragments', () => {
     const ast = parse('fragment a($v: Boolean = false) on t { f }', {
       noLocation: true,
-      allowLegacyFragmentVariables: true,
     });
     const visited: Array<any> = [];
 
@@ -505,6 +504,49 @@ describe('Visitor', () => {
     ]);
   });
 
+  it('visits arguments on fragment spreads', () => {
+    const ast = parse('fragment a on t { ...s(v: false) }', {
+      noLocation: true,
+    });
+    const visited: Array<any> = [];
+
+    visit(ast, {
+      enter(node) {
+        checkVisitorFnArgs(ast, arguments);
+        visited.push(['enter', node.kind, getValue(node)]);
+      },
+      leave(node) {
+        checkVisitorFnArgs(ast, arguments);
+        visited.push(['leave', node.kind, getValue(node)]);
+      },
+    });
+
+    expect(visited).to.deep.equal([
+      ['enter', 'Document', undefined],
+      ['enter', 'FragmentDefinition', undefined],
+      ['enter', 'Name', 'a'],
+      ['leave', 'Name', 'a'],
+      ['enter', 'NamedType', undefined],
+      ['enter', 'Name', 't'],
+      ['leave', 'Name', 't'],
+      ['leave', 'NamedType', undefined],
+      ['enter', 'SelectionSet', undefined],
+      ['enter', 'FragmentSpread', undefined],
+      ['enter', 'Name', 's'],
+      ['leave', 'Name', 's'],
+      ['enter', 'Argument', { kind: 'BooleanValue', value: false }],
+      ['enter', 'Name', 'v'],
+      ['leave', 'Name', 'v'],
+      ['enter', 'BooleanValue', false],
+      ['leave', 'BooleanValue', false],
+      ['leave', 'Argument', { kind: 'BooleanValue', value: false }],
+      ['leave', 'FragmentSpread', undefined],
+      ['leave', 'SelectionSet', undefined],
+      ['leave', 'FragmentDefinition', undefined],
+      ['leave', 'Document', undefined],
+    ]);
+  });
+
   it('n', () => {
     const ast = parse(kitchenSinkQuery, {
       experimentalClientControlledNullability: true,