josdejong/jsoneditor

"Cannot read properties of null (reading 'getInternalPath')"

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#1498 opened on Feb 16, 2023

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 (3 comments) (0 reactions) (0 assignees)JavaScript (10,781 stars) (2,034 forks)batch import
bughelp wanted

Description

I'm sporadically getting the following error when I change object keys (not values):

TypeError: Cannot read properties of null (reading 'getInternalPath')
S.value
https://76uwry.csb.app/node_modules/jsoneditor/dist/jsoneditor.min.js:33:36942
eval
https://76uwry.csb.app/node_modules/jsoneditor/dist/jsoneditor.min.js:35:2194

See https://codesandbox.io/s/jsoneditor-debounced-error-76uwry for an example: Try changing hello. (This calls setValue extremely fast to demonstrate the problem.)

I believe that the problem is caused by a race condition: Edits are propagated with a 150ms delay (due to the use of debounce), so, if the editor receives a new value, the old value has been removed and no longer has the fields that the event handler expects it to have.

https://github.com/josdejong/jsoneditor/blob/v9.9.2/src/js/Node.js#L1649

I'm not sure if the correct fix is to cancel debounced events when a node is removed (e.g., Lodash's debounce has a cancel function; a similar idea could be added here) or make the events check for, e.g., this.parent == null.

Contributor guide

Tech stack
javascriptnodejs
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
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.
mostly clear
Prerequisites
Understanding of JavaScriptKnowledge of debounce
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate the race condition in the debounced event propagation. Look at the source file src/js/Node.js, specifically line 1649. Consider either adding a method to cancel debounced events when a node is removed (similar to Lodash's debounce.cancel) or adding a null check for this.parent. Check the linked CodeSandbox for reproduction.