power-assert-js/power-assert

`Cannot assign to read only property 'ok' of object '[object Object]'` while running in browser

kim366 opened this issue · 3 comments

kim366 commented

Hello. I am trying to run power-assert in the browser using webpack and babel. The code transformation works great, but there is an error pointing to the return statement of the following line:

https://github.com/power-assert-js/power-assert/blob/master/build/power-assert.js#L13557

Here comes the stack trace:

Uncaught TypeError: Cannot assign to read only property 'ok' of object '[object Object]'
    at assign (<anonymous>)
    at eval (eval at empowerAssertObject (power-assert.js:4495), <anonymous>:1:1)
    at empowerAssertObject (power-assert.js:4495)
    at empowerCore (power-assert.js:4482)
    at empower (power-assert.js:4663)
    at applyEmpower (power-assert.js:17203)
    at customize (power-assert.js:17209)
    at power-assert.js:17226
    at createCommonjsModule (_commonjsHelpers-4f955397.js:14)
    at power-assert.js:17172
twada commented

@kim366 Thank you for reporting!
I'll take a look.
Would you make a small repository or gist for reproduction of this case?

kim366 commented

Yes, of course. Here it is: https://github.com/kim366/repro-power-assert

  1. git clone https://github.com/kim366/repro-power-assert.git
  2. npm install && npm start
  3. Open http://localhost:8080/test/TestRunner.html
  4. Open Devtools

Hope this helps.

  • ❤️1
twada commented

Thank you for your repro case.

I've found that Rollup, where used internally by Snowpack, freezes assert module by default.

var assert$1 = /*#__PURE__*/Object.freeze({
  __proto__: null,
  'default': assert,
  AssertionError: AssertionError,
  fail: fail,
  ok: ok,
  assert: ok,
  equal: equal,
  notEqual: notEqual,
  deepEqual: deepEqual,
  deepStrictEqual: deepStrictEqual,
  notDeepEqual: notDeepEqual,
  notDeepStrictEqual: notDeepStrictEqual,
  strictEqual: strictEqual,
  notStrictEqual: notStrictEqual,
  throws: throws,
  doesNotThrow: doesNotThrow,
  ifError: ifError
});

Also found that Rollup has a freeze option for opting-out of Object.freeze usage.
refs: rollup/rollup#1696

So if you can pass freeze option to Rollup via Snowpack, power-assert might work.

  • 🎉1