zalmoxisus/redux-devtools-extension

Sets aren't properly diffed or displayed

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#452 opened on Jan 30, 2018

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 (1 comment) (8 reactions) (0 assignees)JavaScript (13,478 stars) (1,074 forks)batch import
help wantedmonitor

Description

Just wanted to make you aware of a possible bug. When passing a new set as a key of the initial state:

{
  items: new Set()
}

and then later adding to the set like so:

const newItems = new Set(state.items)
newItems.add("newItem")
return {...state, items: newItems}

the redux devtools evaluates the diff as no change, while logging the state shows that an item was added.

Let me know if you want any more details about this bug. I have a workaround that I'm using to log the items when needed, but thought you might want to know.

Contributor guide

Tech stack
javascriptreact
Domain
frontend
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
Understanding of Redux DevTools extensionFamiliarity with JavaScript Set and object diffing
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate how the Redux DevTools extension computes state diffs. The issue likely lies in the diffing logic that may not handle non plain objects like Set. Look for files related to state comparison or diffing, such as 'src/browser/extension/inject/diff.js' or similar. Check if the extension uses JSON.stringify or a custom deep equal function that fails on Set. Consider implementing a custom diff that handles Set by converting to array or using iterator.