fast-json-patch@2.2.0 is incorrectly presenting as a transpiled ES Module #233
Description
fast-json-patch@2.2.0 is breaking builds in Swagger Client (see swagger-api/swagger-js#1460).
Current behavior
The problem is that fast-json-patch is combining the __esModule hint with an exports object that follows the CJS exports pattern.
2.2.0 is setting an non-enumerable __esModule hint property that wasn't present before:
➜ node -e 'const fjp = require("fast-json-patch"); const util = require("util"); console.log(util.inspect(fjp, { showHidden: true, depth: 0 }));'
{ [__esModule]: true,
applyOperation: [Object],
applyPatch: [Object],
applyReducer: [Object],
getValueByPointer: [Object],
validate: [Object],
validator: [Object],
JsonPatchError: [Object],
deepClone: [Object],
escapePathComponent: [Object],
unescapePathComponent: [Object],
unobserve: [Object],
observe: [Object],
generate: [Object],
compare: [Object] }This property is used in transpilers and module loaders to handle interoperability between CJS modules and ESM modules represented as JavaScript objects -- specifically, CJS modules need to be wrapped inside another object's default property. More info here.
All of this means that when I use import syntax to use fast-json-patch in my Babel-enabled project:
import fastJsonPatch from "fast-json-patch"
fastJsonPatch.applyOperation()...Babel translates my import to:
var _fastJsonPatch = _interopRequireDefault(require("fast-json-patch"));
function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }
_fastJsonPatch["default"].applyPatch();...which means at runtime, my code will see __esModule: true in fast-json-patch and therefore not wrap the exported result from it in a default key:
➜ node -e 'var _fastJsonPatch = _interopRequireDefault(require("fast-json-patch")); function _interopRequireDefault(obj) { return obj && obj.__esModule ? obj : { "default": obj }; }; _fastJsonPatch["default"].applyPatch();'
[eval]:5
_fastJsonPatch["default"].applyPatch();
^
TypeError: Cannot read property 'applyPatch' of undefined
at [eval]:5:27
at ContextifyScript.Script.runInThisContext (vm.js:50:33)
at Object.runInThisContext (vm.js:139:38)
at Object.<anonymous> ([eval]-wrapper:6:22)
at Module._compile (module.js:652:30)
at evalScript (bootstrap_node.js:466:27)
at startup (bootstrap_node.js:167:9)
at bootstrap_node.js:612:3Expected behavior
fast-json-patch should either be not setting __esModule (which was the previous behavior), or should be exporting an object that matches ESM syntax, e.g. { __esModule: true, default: { applyOperation: [Object], ... } }.