remove-empty-nodes.ts

import { visit } from 'graphql';
import { DocumentOptimizer } from '../types.js';

/**
 * This optimizer removes empty nodes/arrays (directives/argument/variableDefinitions) from a given DocumentNode of operation/fragment.
 * @param input
 */
export const removeEmptyNodes: DocumentOptimizer = input => {
  function transformNode(node: any) {
    let resultNode = node;

    if (
      resultNode.directives &&
      Array.isArray(resultNode.directives) &&
      resultNode.directives.length === 0
    ) {
      const { directives, ...rest } = resultNode;

      resultNode = rest;
    }

    if (
      resultNode.arguments &&
      Array.isArray(resultNode.arguments) &&
      resultNode.arguments.length === 0
    ) {
      const { arguments: args, ...rest } = resultNode;

      resultNode = rest;
    }

    if (
      resultNode.variableDefinitions &&
      Array.isArray(resultNode.variableDefinitions) &&
      resultNode.variableDefinitions.length === 0
    ) {
      const { variableDefinitions, ...rest } = resultNode;

      resultNode = rest;
    }

    return resultNode;
  }

  return visit(input, {
    // Request/Operation:
    FragmentDefinition: transformNode,
    OperationDefinition: transformNode,
    VariableDefinition: transformNode,
    Field: transformNode,
    FragmentSpread: transformNode,
    InlineFragment: transformNode,
    Name: transformNode,
    Directive: transformNode,
    // Schema Definition:
    SchemaDefinition: transformNode,
    ScalarTypeDefinition: transformNode,
    ObjectTypeDefinition: transformNode,
    InterfaceTypeDefinition: transformNode,
    UnionTypeDefinition: transformNode,
    EnumTypeDefinition: transformNode,
    EnumValueDefinition: transformNode,
    InputObjectTypeDefinition: transformNode,
    FieldDefinition: transformNode,
    InputValueDefinition: transformNode,
    // Schema Extension:
    SchemaExtension: transformNode,
    ScalarTypeExtension: transformNode,
    ObjectTypeExtension: transformNode,
    InterfaceTypeExtension: transformNode,
    UnionTypeExtension: transformNode,
    EnumTypeExtension: transformNode,
    InputObjectTypeExtension: transformNode,
  });
};