rtfeldman/seamless-immutable

`merge` ignores Symbols contrary to `set`

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#189 opened on Dec 28, 2016

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bughelp wanted

Description

Using Immutable 7.0.1, Babel, and Node 6, it seems that merge skips properties where the key is a Symbol, while set (correctly) sets them. It works with normal objects. Example:

babel> const Immutable =  require('seamless-immutable');
babel> const s = Symbol("sym mine");
babel> Immutable({}).merge({[s]: "sym val"})[s]
undefined // WRONG: expected 'sym val'
babel> Immutable({}).set(s, "sym val")[s]
'sym val' // CORRECT

However it works when the key is not a Symbol but a normal object:

> var Immutable =  require('seamless-immutable');
> var s = {name: "key obj"};
> Immutable({}).merge({[s]: "sym val"})[s]
'sym val'

Contributor guide

Tech stack
javascriptnodejs
Domain
full stack
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.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaScript Symbolsseamless immutable merge function
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Investigate the 'merge' function in the source code (likely in 'src/merge.js' or similar). The bug is that merge does not include Symbol keyed properties. Compare how 'set' handles Symbols. The fix should add iteration over Symbol keys in the merge logic, e.g., using Object.getOwnPropertySymbols.