PossibleTypeExtensionsRule.ts

import { didYouMean } from '../../jsutils/didYouMean';
import { inspect } from '../../jsutils/inspect';
import { invariant } from '../../jsutils/invariant';
import type { ObjMap } from '../../jsutils/ObjMap';
import { suggestionList } from '../../jsutils/suggestionList';

import { GraphQLError } from '../../error/GraphQLError';

import type { DefinitionNode, TypeExtensionNode } from '../../language/ast';
import { Kind } from '../../language/kinds';
import { isTypeDefinitionNode } from '../../language/predicates';
import type { ASTVisitor } from '../../language/visitor';

import type { GraphQLNamedType } from '../../type/definition';
import {
  isEnumType,
  isInputObjectType,
  isInterfaceType,
  isObjectType,
  isScalarType,
  isUnionType,
} from '../../type/definition';

import type { SDLValidationContext } from '../ValidationContext';

/**
 * Possible type extension
 *
 * A type extension is only valid if the type is defined and has the same kind.
 */
export function PossibleTypeExtensionsRule(
  context: SDLValidationContext,
): ASTVisitor {
  const schema = context.getSchema();
  const definedTypes: ObjMap<DefinitionNode> = Object.create(null);

  for (const def of context.getDocument().definitions) {
    if (isTypeDefinitionNode(def)) {
      definedTypes[def.name.value] = def;
    }
  }

  return {
    ScalarTypeExtension: checkExtension,
    ObjectTypeExtension: checkExtension,
    InterfaceTypeExtension: checkExtension,
    UnionTypeExtension: checkExtension,
    EnumTypeExtension: checkExtension,
    InputObjectTypeExtension: checkExtension,
  };

  function checkExtension(node: TypeExtensionNode): void {
    const typeName = node.name.value;
    const defNode = definedTypes[typeName];
    const existingType = schema?.getType(typeName);

    let expectedKind: Kind | undefined;
    if (defNode) {
      expectedKind = defKindToExtKind[defNode.kind];
    } else if (existingType) {
      expectedKind = typeToExtKind(existingType);
    }

    if (expectedKind) {
      if (expectedKind !== node.kind) {
        const kindStr = extensionKindToTypeName(node.kind);
        context.reportError(
          new GraphQLError(
            `Cannot extend non-${kindStr} type "${typeName}".`,
            defNode ? [defNode, node] : node,
          ),
        );
      }
    } else {
      const allTypeNames = Object.keys({
        ...definedTypes,
        ...schema?.getTypeMap(),
      });

      const suggestedTypes = suggestionList(typeName, allTypeNames);
      context.reportError(
        new GraphQLError(
          `Cannot extend type "${typeName}" because it is not defined.` +
            didYouMean(suggestedTypes),
          node.name,
        ),
      );
    }
  }
}

const defKindToExtKind: ObjMap<Kind> = {
  [Kind.SCALAR_TYPE_DEFINITION]: Kind.SCALAR_TYPE_EXTENSION,
  [Kind.OBJECT_TYPE_DEFINITION]: Kind.OBJECT_TYPE_EXTENSION,
  [Kind.INTERFACE_TYPE_DEFINITION]: Kind.INTERFACE_TYPE_EXTENSION,
  [Kind.UNION_TYPE_DEFINITION]: Kind.UNION_TYPE_EXTENSION,
  [Kind.ENUM_TYPE_DEFINITION]: Kind.ENUM_TYPE_EXTENSION,
  [Kind.INPUT_OBJECT_TYPE_DEFINITION]: Kind.INPUT_OBJECT_TYPE_EXTENSION,
};

function typeToExtKind(type: GraphQLNamedType): Kind {
  if (isScalarType(type)) {
    return Kind.SCALAR_TYPE_EXTENSION;
  }
  if (isObjectType(type)) {
    return Kind.OBJECT_TYPE_EXTENSION;
  }
  if (isInterfaceType(type)) {
    return Kind.INTERFACE_TYPE_EXTENSION;
  }
  if (isUnionType(type)) {
    return Kind.UNION_TYPE_EXTENSION;
  }
  if (isEnumType(type)) {
    return Kind.ENUM_TYPE_EXTENSION;
  }
  if (isInputObjectType(type)) {
    return Kind.INPUT_OBJECT_TYPE_EXTENSION;
  }
  /* c8 ignore next 3 */
  // Not reachable. All possible types have been considered
  invariant(false, 'Unexpected type: ' + inspect(type));
}

function extensionKindToTypeName(kind: Kind): string {
  switch (kind) {
    case Kind.SCALAR_TYPE_EXTENSION:
      return 'scalar';
    case Kind.OBJECT_TYPE_EXTENSION:
      return 'object';
    case Kind.INTERFACE_TYPE_EXTENSION:
      return 'interface';
    case Kind.UNION_TYPE_EXTENSION:
      return 'union';
    case Kind.ENUM_TYPE_EXTENSION:
      return 'enum';
    case Kind.INPUT_OBJECT_TYPE_EXTENSION:
      return 'input object';
    // Not reachable. All possible types have been considered
    /* c8 ignore next */
    default:
      invariant(false, 'Unexpected kind: ' + inspect(kind));
  }
}