graphql/validation/rules/UniqueFieldDefinitionNamesRule.mjs

import { GraphQLError } from "../../error/GraphQLError.mjs";
import { isObjectType, isInterfaceType, isInputObjectType } from "../../type/definition.mjs";

/**
 * Unique field definition names
 *
 * A GraphQL complex type is only valid if all its fields are uniquely named.
 */
export function UniqueFieldDefinitionNamesRule(context) {
  var schema = context.getSchema();
  var existingTypeMap = schema ? schema.getTypeMap() : Object.create(null);
  var knownFieldNames = Object.create(null);
  return {
    InputObjectTypeDefinition: checkFieldUniqueness,
    InputObjectTypeExtension: checkFieldUniqueness,
    InterfaceTypeDefinition: checkFieldUniqueness,
    InterfaceTypeExtension: checkFieldUniqueness,
    ObjectTypeDefinition: checkFieldUniqueness,
    ObjectTypeExtension: checkFieldUniqueness
  };

  function checkFieldUniqueness(node) {
    var _node$fields;

    var typeName = node.name.value;

    if (!knownFieldNames[typeName]) {
      knownFieldNames[typeName] = Object.create(null);
    } // istanbul ignore next (See: 'https://github.com/graphql/graphql-js/issues/2203')


    var fieldNodes = (_node$fields = node.fields) !== null && _node$fields !== void 0 ? _node$fields : [];
    var fieldNames = knownFieldNames[typeName];

    for (var _i2 = 0; _i2 < fieldNodes.length; _i2++) {
      var fieldDef = fieldNodes[_i2];
      var fieldName = fieldDef.name.value;

      if (hasField(existingTypeMap[typeName], fieldName)) {
        context.reportError(new GraphQLError("Field \"".concat(typeName, ".").concat(fieldName, "\" already exists in the schema. It cannot also be defined in this type extension."), fieldDef.name));
      } else if (fieldNames[fieldName]) {
        context.reportError(new GraphQLError("Field \"".concat(typeName, ".").concat(fieldName, "\" can only be defined once."), [fieldNames[fieldName], fieldDef.name]));
      } else {
        fieldNames[fieldName] = fieldDef.name;
      }
    }

    return false;
  }
}

function hasField(type, fieldName) {
  if (isObjectType(type) || isInterfaceType(type) || isInputObjectType(type)) {
    return type.getFields()[fieldName] != null;
  }

  return false;
}