rtfeldman/seamless-immutable

Doesn't play well with Symbols (generators?)

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#107 opened on Mar 1, 2016

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 (2 comments) (0 reactions) (0 assignees)JavaScript (5,367 stars) (221 forks)batch import
bughelp wanted

Description

Great library. I have a pretty esoteric case, but the failure seems to be real.

This code:

let context = {
    * [Symbol.iterator]() {
        yield Promise.resolve(1);
        yield Promise.resolve(2);
    }
};

for (let P of context) {
    console.log(P.value());
}

// 1
// 2

Fails if wrapped by Immutable:

let context = Immutable({
    * [Symbol.iterator]() {
        yield Promise.resolve(1);
        yield Promise.resolve(2);
    }
});

...

for (let P of context) {
              ^
TypeError: undefined is not a function

I'm not sure if it is the generator or the symbol usage (or computed property keys or the compact object method signature) that's causing the problem.

Running on Node (5.x), with --harmony flag. Also, bluebird is the Promise implementation.

Contributor guide

Tech stack
javascript
Domain
data
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
basic knowledge of JavaScript generatorsunderstanding of Symbol.iterator
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
25
Research direction
Examine the `Immutable` function in `lib/seamless immutable.js`. Determine how it copies properties from the original object. The issue is that computed property keys (Symbols) are not handled, specifically for generators. Review if the library skips Symbol keyed properties or if there's a bug in handling generator methods. Look at existing tests for Symbol.iterator to see if any exist.