Add Node Predicates

src/index.js

@@ -189,6 +189,16 @@ export {
   TokenKind,
   DirectiveLocation,
   BREAK,
+  // Predicates
+  isDefinitionNode,
+  isExecutableDefinitionNode,
+  isSelectionNode,
+  isValueNode,
+  isTypeNode,
+  isTypeSystemDefinitionNode,
+  isTypeDefinitionNode,
+  isTypeSystemExtensionNode,
+  isTypeExtensionNode,
 } from './language';
 
 export type {

src/language/index.js

@@ -88,5 +88,17 @@ export type {
   InputObjectTypeExtensionNode,
 } from './ast';
 
+export {
+  isDefinitionNode,
+  isExecutableDefinitionNode,
+  isSelectionNode,
+  isValueNode,
+  isTypeNode,
+  isTypeSystemDefinitionNode,
+  isTypeDefinitionNode,
+  isTypeSystemExtensionNode,
+  isTypeExtensionNode,
+} from './predicates';
+
 export { DirectiveLocation } from './directiveLocation';
 export type { DirectiveLocationEnum } from './directiveLocation';

src/language/predicates.js

@@ -0,0 +1,90 @@
+/**
+ * Copyright (c) 2018-present, Facebook, Inc.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ */
+
+import type { ASTNode } from './ast';
+import { Kind } from './kinds';
+
+export function isDefinitionNode(node: ASTNode): boolean %checks {
+  return (
+    isExecutableDefinitionNode(node) ||
+    isTypeSystemDefinitionNode(node) ||
+    isTypeSystemExtensionNode(node)
+  );
+}
+
+export function isExecutableDefinitionNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.OPERATION_DEFINITION ||
+    node.kind === Kind.FRAGMENT_DEFINITION
+  );
+}
+
+export function isSelectionNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.FIELD ||
+    node.kind === Kind.FRAGMENT_SPREAD ||
+    node.kind === Kind.INLINE_FRAGMENT
+  );
+}
+
+export function isValueNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.INT ||
+    node.kind === Kind.FLOAT ||
+    node.kind === Kind.STRING ||
+    node.kind === Kind.BOOLEAN ||
+    node.kind === Kind.NULL ||
+    node.kind === Kind.ENUM ||
+    node.kind === Kind.LIST ||
+    node.kind === Kind.OBJECT ||
+    node.kind === Kind.OBJECT_FIELD
+  );
+}
+
+export function isTypeNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.NAMED_TYPE ||
+    node.kind === Kind.LIST_TYPE ||
+    node.kind === Kind.NON_NULL_TYPE
+  );
+}
+
+export function isTypeSystemDefinitionNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.SCHEMA_DEFINITION ||
+    isTypeDefinitionNode(node) ||
+    node.kind === Kind.DIRECTIVE_DEFINITION
+  );
+}
+
+export function isTypeDefinitionNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.SCALAR_TYPE_DEFINITION ||
+    node.kind === Kind.OBJECT_TYPE_DEFINITION ||
+    node.kind === Kind.INTERFACE_TYPE_DEFINITION ||
+    node.kind === Kind.UNION_TYPE_DEFINITION ||
+    node.kind === Kind.ENUM_TYPE_DEFINITION ||
+    node.kind === Kind.INPUT_OBJECT_TYPE_DEFINITION
+  );
+}
+
+export function isTypeSystemExtensionNode(node: ASTNode): boolean %checks {
+  return node.kind === Kind.SCHEMA_EXTENSION || isTypeExtensionNode(node);
+}
+
+export function isTypeExtensionNode(node: ASTNode): boolean %checks {
+  return (
+    node.kind === Kind.SCALAR_TYPE_EXTENSION ||
+    node.kind === Kind.OBJECT_TYPE_EXTENSION ||
+    node.kind === Kind.INTERFACE_TYPE_EXTENSION ||
+    node.kind === Kind.UNION_TYPE_EXTENSION ||
+    node.kind === Kind.ENUM_TYPE_EXTENSION ||
+    node.kind === Kind.INPUT_OBJECT_TYPE_EXTENSION
+  );
+}

src/utilities/buildASTSchema.js

@@ -40,6 +40,7 @@ import type {
   StringValueNode,
   Location,
 } from '../language/ast';
+import { isTypeDefinitionNode } from '../language/predicates';
 
 import type { DirectiveLocationEnum } from '../language/directiveLocation';
 
@@ -132,27 +133,18 @@ export function buildASTSchema(
   const nodeMap: ObjMap<TypeDefinitionNode> = Object.create(null);
   const directiveDefs: Array<DirectiveDefinitionNode> = [];
   for (let i = 0; i < documentAST.definitions.length; i++) {
-    const d = documentAST.definitions[i];
-    switch (d.kind) {
-      case Kind.SCHEMA_DEFINITION:
-        schemaDef = d;
-        break;
-      case Kind.SCALAR_TYPE_DEFINITION:
-      case Kind.OBJECT_TYPE_DEFINITION:
-      case Kind.INTERFACE_TYPE_DEFINITION:
-      case Kind.ENUM_TYPE_DEFINITION:
-      case Kind.UNION_TYPE_DEFINITION:
-      case Kind.INPUT_OBJECT_TYPE_DEFINITION:
-        const typeName = d.name.value;
-        if (nodeMap[typeName]) {
-          throw new Error(`Type "${typeName}" was defined more than once.`);
-        }
-        typeDefs.push(d);
-        nodeMap[typeName] = d;
-        break;
-      case Kind.DIRECTIVE_DEFINITION:
-        directiveDefs.push(d);
-        break;
+    const def = documentAST.definitions[i];
+    if (def.kind === Kind.SCHEMA_DEFINITION) {
+      schemaDef = def;
+    } else if (isTypeDefinitionNode(def)) {
+      const typeName = def.name.value;
+      if (nodeMap[typeName]) {
+        throw new Error(`Type "${typeName}" was defined more than once.`);
+      }
+      typeDefs.push(def);
+      nodeMap[typeName] = def;
+    } else if (def.kind === Kind.DIRECTIVE_DEFINITION) {
+      directiveDefs.push(def);
     }
   }
 

src/utilities/extendSchema.js

@@ -56,6 +56,10 @@ import type {
   SchemaExtensionNode,
   SchemaDefinitionNode,
 } from '../language/ast';
+import {
+  isTypeDefinitionNode,
+  isTypeExtensionNode,
+} from '../language/predicates';
 
 type Options = {|
   ...GraphQLSchemaValidationOptions,
@@ -125,67 +129,51 @@ export function extendSchema(
 
   for (let i = 0; i < documentAST.definitions.length; i++) {
     const def = documentAST.definitions[i];
-    switch (def.kind) {
-      case Kind.SCHEMA_DEFINITION:
-        schemaDef = def;
-        break;
-      case Kind.SCHEMA_EXTENSION:
-        schemaExtensions.push(def);
-        break;
-      case Kind.OBJECT_TYPE_DEFINITION:
-      case Kind.INTERFACE_TYPE_DEFINITION:
-      case Kind.ENUM_TYPE_DEFINITION:
-      case Kind.UNION_TYPE_DEFINITION:
-      case Kind.SCALAR_TYPE_DEFINITION:
-      case Kind.INPUT_OBJECT_TYPE_DEFINITION:
-        // Sanity check that none of the defined types conflict with the
-        // schema's existing types.
-        const typeName = def.name.value;
-        if (schema.getType(typeName)) {
-          throw new GraphQLError(
-            `Type "${typeName}" already exists in the schema. It cannot also ` +
-              'be defined in this type definition.',
-            [def],
-          );
-        }
-        typeDefinitionMap[typeName] = def;
-        break;
-      case Kind.SCALAR_TYPE_EXTENSION:
-      case Kind.OBJECT_TYPE_EXTENSION:
-      case Kind.INTERFACE_TYPE_EXTENSION:
-      case Kind.ENUM_TYPE_EXTENSION:
-      case Kind.INPUT_OBJECT_TYPE_EXTENSION:
-      case Kind.UNION_TYPE_EXTENSION:
-        // Sanity check that this type extension exists within the
-        // schema's existing types.
-        const extendedTypeName = def.name.value;
-        const existingType = schema.getType(extendedTypeName);
-        if (!existingType) {
-          throw new GraphQLError(
-            `Cannot extend type "${extendedTypeName}" because it does not ` +
-              'exist in the existing schema.',
-            [def],
-          );
-        }
-        checkExtensionNode(existingType, def);
-
-        const existingTypeExtensions = typeExtensionsMap[extendedTypeName];
-        typeExtensionsMap[extendedTypeName] = existingTypeExtensions
-          ? existingTypeExtensions.concat([def])
-          : [def];
-        break;
-      case Kind.DIRECTIVE_DEFINITION:
-        const directiveName = def.name.value;
-        const existingDirective = schema.getDirective(directiveName);
-        if (existingDirective) {
-          throw new GraphQLError(
-            `Directive "${directiveName}" already exists in the schema. It ` +
-              'cannot be redefined.',
-            [def],
-          );
-        }
-        directiveDefinitions.push(def);
-        break;
+    if (def.kind === Kind.SCHEMA_DEFINITION) {
+      schemaDef = def;
+    } else if (def.kind === Kind.SCHEMA_EXTENSION) {
+      schemaExtensions.push(def);
+    } else if (isTypeDefinitionNode(def)) {
+      // Sanity check that none of the defined types conflict with the
+      // schema's existing types.
+      const typeName = def.name.value;
+      if (schema.getType(typeName)) {
+        throw new GraphQLError(
+          `Type "${typeName}" already exists in the schema. It cannot also ` +
+            'be defined in this type definition.',
+          [def],
+        );
+      }
+      typeDefinitionMap[typeName] = def;
+    } else if (isTypeExtensionNode(def)) {
+      // Sanity check that this type extension exists within the
+      // schema's existing types.
+      const extendedTypeName = def.name.value;
+      const existingType = schema.getType(extendedTypeName);
+      if (!existingType) {
+        throw new GraphQLError(
+          `Cannot extend type "${extendedTypeName}" because it does not ` +
+            'exist in the existing schema.',
+          [def],
+        );
+      }
+      checkExtensionNode(existingType, def);
+
+      const existingTypeExtensions = typeExtensionsMap[extendedTypeName];
+      typeExtensionsMap[extendedTypeName] = existingTypeExtensions
+        ? existingTypeExtensions.concat([def])
+        : [def];
+    } else if (def.kind === Kind.DIRECTIVE_DEFINITION) {
+      const directiveName = def.name.value;
+      const existingDirective = schema.getDirective(directiveName);
+      if (existingDirective) {
+        throw new GraphQLError(
+          `Directive "${directiveName}" already exists in the schema. It ` +
+            'cannot be redefined.',
+          [def],
+        );
+      }
+      directiveDefinitions.push(def);
     }
   }
 

src/validation/rules/ExecutableDefinitions.js

@@ -10,6 +10,7 @@
 import type { ASTValidationContext } from '../ValidationContext';
 import { GraphQLError } from '../../error';
 import { Kind } from '../../language/kinds';
+import { isExecutableDefinitionNode } from '../../language/predicates';
 import type { ASTVisitor } from '../../language/visitor';
 
 export function nonExecutableDefinitionMessage(defName: string): string {
@@ -28,10 +29,7 @@ export function ExecutableDefinitions(
   return {
     Document(node) {
       for (const definition of node.definitions) {
-        if (
-          definition.kind !== Kind.OPERATION_DEFINITION &&
-          definition.kind !== Kind.FRAGMENT_DEFINITION
-        ) {
+        if (!isExecutableDefinitionNode(definition)) {
           context.reportError(
             new GraphQLError(
               nonExecutableDefinitionMessage(