Iterating over Python iterables from TypeScript always returns undefined for the iterator value

[mmomtchev]

Consider the following TypeScript code:

import { PyObject } from 'pymport/proxified';

const d = PyObject.dict({a: 1, b: 2});
for (const i of d) console.log(i);

Instead of outputting

a
b

it outputs

undefined
undefined

[mmomtchev]

This is in fact a TypeScript issue, by default tsc transpiles this to the following JS code:

"use strict";
exports.__esModule = true;
var proxified_1 = require("pymport/proxified");
var d = proxified_1.PyObject.dict({ a: 1, b: 2 });
for (var _i = 0, d_1 = d; _i < d_1.length; _i++) {
    var i = d_1[_i];
    console.log(i);
}

which explains the output - a d is an iterable but not a subscriptable.

Use the TypeScript transpiler option "downlevelIteration": true to achieve correct behavior.