Open
Description
Consider these two functions.
def multiply(a, b=1):
return a * b
async def multiply_async(a, b=1):
return a * bCompiled to JS, they are:
// Transcrypt'ed from Python, 2024-09-01 01:05:45
import {AssertionError, AttributeError, BaseException, DeprecationWarning, Exception, IndexError, IterableError, KeyError, NotImplementedError, RuntimeWarning, StopIteration, UserWarning, ValueError, Warning, __JsIterator__, __PyIterator__, __Terminal__, __add__, __and__, __call__, __class__, __envir__, __eq__, __floordiv__, __ge__, __get__, __getcm__, __getitem__, __getslice__, __getsm__, __gt__, __i__, __iadd__, __iand__, __idiv__, __ijsmod__, __ilshift__, __imatmul__, __imod__, __imul__, __in__, __init__, __ior__, __ipow__, __irshift__, __isub__, __ixor__, __jsUsePyNext__, __jsmod__, __k__, __kwargtrans__, __le__, __lshift__, __lt__, __matmul__, __mergefields__, __mergekwargtrans__, __mod__, __mul__, __ne__, __neg__, __nest__, __or__, __pow__, __pragma__, __pyUseJsNext__, __rshift__, __setitem__, __setproperty__, __setslice__, __sort__, __specialattrib__, __sub__, __super__, __t__, __terminal__, __truediv__, __withblock__, __xor__, _sort, abs, all, any, assert, bin, bool, bytearray, bytes, callable, chr, delattr, dict, dir, divmod, enumerate, filter, float, getattr, hasattr, hex, input, int, isinstance, issubclass, len, list, map, max, min, object, oct, ord, pow, print, property, py_TypeError, py_iter, py_metatype, py_next, py_reversed, py_typeof, range, repr, round, set, setattr, sorted, str, sum, tuple, zip} from './org.transcrypt.__runtime__.js';
var __name__ = '__main__';
export var multiply = function (a, b) {
if (typeof b == 'undefined' || (b != null && b.hasOwnProperty ("__kwargtrans__"))) {;
var b = 1;
};
return a * b;
};
export var multiply_async = async function (a, b) {
if (typeof b == 'undefined' || (b != null && b.hasOwnProperty ("__kwargtrans__"))) {;
var b = 1;
};
return a * b;
};Now, let's test those 2 functions:
console.log('multiply')
console.log(multiply(5, 2))
console.log(multiply(5))
console.log('multiply_async:')
multiply_async(5, 2).then(console.log)
multiply_async(5).then(console.log)In Chrome and Node, the output is:
multiply:
10
5
multiply_async:
10
5
But in Safari, the output is:
multiply:
10
5
multiply_async:
5
5
This is due to redeclaring b (var b = 1;), when b was already defined as the parameter of the function. In normal written Javascript, we would just reassign (b = 1).
Someone else has noticed this before:
https://medium.com/@alsotang/a-hoisting-bug-in-the-async-function-in-safari-ba1ecc386b4a
Therefore, it is not safe to re-declare function parameters using var