Refine parse and AST to represent ConstValue (#3059)

This adds:

* ConstValueNode - A subtype of ValueNode which recursively excludes Variables
* Improved syntax error when encountering variable in a const value
* parseConstValue(): ConstValueNode
* isConstValue(): ConstValueNode
* Various refinements to AST types to use ConstValueNode (or a type which includes it) to better align to the spec.

Author: leebyron

src/index.d.ts

@@ -200,6 +200,7 @@ export {
   // Parse
   parse,
   parseValue,
+  parseConstValue,
   parseType,
   // Print
   print,
@@ -215,6 +216,7 @@ export {
   isExecutableDefinitionNode,
   isSelectionNode,
   isValueNode,
+  isConstValueNode,
   isTypeNode,
   isTypeSystemDefinitionNode,
   isTypeDefinitionNode,
@@ -247,20 +249,26 @@ export {
   SelectionNode,
   FieldNode,
   ArgumentNode,
+  ConstArgumentNode,
   FragmentSpreadNode,
   InlineFragmentNode,
   FragmentDefinitionNode,
   ValueNode,
+  ConstValueNode,
   IntValueNode,
   FloatValueNode,
   StringValueNode,
   BooleanValueNode,
   NullValueNode,
   EnumValueNode,
   ListValueNode,
+  ConstListValueNode,
   ObjectValueNode,
+  ConstObjectValueNode,
   ObjectFieldNode,
+  ConstObjectFieldNode,
   DirectiveNode,
+  ConstDirectiveNode,
   TypeNode,
   NamedTypeNode,
   ListTypeNode,

src/index.js

@@ -187,6 +187,7 @@ export {
   // Parse
   parse,
   parseValue,
+  parseConstValue,
   parseType,
   // Print
   print,
@@ -202,6 +203,7 @@ export {
   isExecutableDefinitionNode,
   isSelectionNode,
   isValueNode,
+  isConstValueNode,
   isTypeNode,
   isTypeSystemDefinitionNode,
   isTypeDefinitionNode,
@@ -234,20 +236,26 @@ export type {
   SelectionNode,
   FieldNode,
   ArgumentNode,
+  ConstArgumentNode,
   FragmentSpreadNode,
   InlineFragmentNode,
   FragmentDefinitionNode,
   ValueNode,
+  ConstValueNode,
   IntValueNode,
   FloatValueNode,
   StringValueNode,
   BooleanValueNode,
   NullValueNode,
   EnumValueNode,
   ListValueNode,
+  ConstListValueNode,
   ObjectValueNode,
+  ConstObjectValueNode,
   ObjectFieldNode,
+  ConstObjectFieldNode,
   DirectiveNode,
+  ConstDirectiveNode,
   TypeNode,
   NamedTypeNode,
   ListTypeNode,

src/language/__tests__/parser-test.js

@@ -9,7 +9,7 @@ import { inspect } from '../../jsutils/inspect';
 import { Kind } from '../kinds';
 import { Source } from '../source';
 import { TokenKind } from '../tokenKind';
-import { parse, parseValue, parseType } from '../parser';
+import { parse, parseValue, parseConstValue, parseType } from '../parser';
 
 import { toJSONDeep } from './toJSONDeep';
 
@@ -95,7 +95,7 @@ describe('Parser', () => {
     expectSyntaxError(
       'query Foo($x: Complex = { a: { b: [ $var ] } }) { field }',
     ).to.deep.equal({
-      message: 'Syntax Error: Unexpected "$".',
+      message: 'Syntax Error: Unexpected variable "$var" in constant value.',
       locations: [{ line: 1, column: 37 }],
     });
   });
@@ -447,6 +447,94 @@ describe('Parser', () => {
         ],
       });
     });
+
+    it('allows variables', () => {
+      const result = parseValue('{ field: $var }');
+      expect(toJSONDeep(result)).to.deep.equal({
+        kind: Kind.OBJECT,
+        loc: { start: 0, end: 15 },
+        fields: [
+          {
+            kind: Kind.OBJECT_FIELD,
+            loc: { start: 2, end: 13 },
+            name: {
+              kind: Kind.NAME,
+              loc: { start: 2, end: 7 },
+              value: 'field',
+            },
+            value: {
+              kind: Kind.VARIABLE,
+              loc: { start: 9, end: 13 },
+              name: {
+                kind: Kind.NAME,
+                loc: { start: 10, end: 13 },
+                value: 'var',
+              },
+            },
+          },
+        ],
+      });
+    });
+
+    it('correct message for incomplete variable', () => {
+      expect(() => parseValue('$'))
+        .to.throw()
+        .to.deep.include({
+          message: 'Syntax Error: Expected Name, found <EOF>.',
+          locations: [{ line: 1, column: 2 }],
+        });
+    });
+
+    it('correct message for unexpected token', () => {
+      expect(() => parseValue(':'))
+        .to.throw()
+        .to.deep.include({
+          message: 'Syntax Error: Unexpected ":".',
+          locations: [{ line: 1, column: 1 }],
+        });
+    });
+  });
+
+  describe('parseConstValue', () => {
+    it('parses values', () => {
+      const result = parseConstValue('[123 "abc"]');
+      expect(toJSONDeep(result)).to.deep.equal({
+        kind: Kind.LIST,
+        loc: { start: 0, end: 11 },
+        values: [
+          {
+            kind: Kind.INT,
+            loc: { start: 1, end: 4 },
+            value: '123',
+          },
+          {
+            kind: Kind.STRING,
+            loc: { start: 5, end: 10 },
+            value: 'abc',
+            block: false,
+          },
+        ],
+      });
+    });
+
+    it('does not allow variables', () => {
+      expect(() => parseConstValue('{ field: $var }'))
+        .to.throw()
+        .to.deep.include({
+          message:
+            'Syntax Error: Unexpected variable "$var" in constant value.',
+          locations: [{ line: 1, column: 10 }],
+        });
+    });
+
+    it('correct message for unexpected token', () => {
+      expect(() => parseConstValue('$'))
+        .to.throw()
+        .to.deep.include({
+          message: 'Syntax Error: Unexpected "$".',
+          locations: [{ line: 1, column: 1 }],
+        });
+    });
   });
 
   describe('parseType', () => {

src/language/__tests__/predicates-test.js

@@ -3,11 +3,13 @@ import { describe, it } from 'mocha';
 
 import type { ASTNode } from '../ast';
 import { Kind } from '../kinds';
+import { parseValue } from '../parser';
 import {
   isDefinitionNode,
   isExecutableDefinitionNode,
   isSelectionNode,
   isValueNode,
+  isConstValueNode,
   isTypeNode,
   isTypeSystemDefinitionNode,
   isTypeDefinitionNode,
@@ -75,6 +77,17 @@ describe('AST node predicates', () => {
     ]);
   });
 
+  it('isConstValueNode', () => {
+    expect(isConstValueNode(parseValue('"value"'))).to.equal(true);
+    expect(isConstValueNode(parseValue('$var'))).to.equal(false);
+
+    expect(isConstValueNode(parseValue('{ field: "value" }'))).to.equal(true);
+    expect(isConstValueNode(parseValue('{ field: $var }'))).to.equal(false);
+
+    expect(isConstValueNode(parseValue('[ "value" ]'))).to.equal(true);
+    expect(isConstValueNode(parseValue('[ $var ]'))).to.equal(false);
+  });
+
   it('isTypeNode', () => {
     expect(filterNodes(isTypeNode)).to.deep.equal([
       'NamedType',