react-dropzone/react-dropzone

[BUG] Inconsistency: cases when `isDragReject` is true but `onDrop` later sees as accepted files

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#1244 opened on Oct 19, 2022

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enhancementhelp wanted

Description

When dropping in files conforming to {accept: { 'model/gltf-binary': ['.glb'] }}, I noticed that file.type ends up being an empty string but still set as accepted inside onDrop due to the file extension check. However isDragReject still reports true during the drag. Upon deeper investigation this seems to be due to the fact that the file type list is not available inside the event's dataTransfer during dragenter/dragover yet.

I'm not sure about the root cause, it seems like it happens when dragging in certain less common file MIME types, either the OS or Chrome doesn't report them... (tested on MacOS 12.5.1 / Chrome ). It also happens when dragging in folders (#977), and is mentioned in several issues (for example, #25, #276).

I would like to suggest (and offer) to implement isDragUnknown to offer better end-user feedback, in situations where the drag is ambious. What do you think?

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.
1-3 hours
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
ReactDrag and drop eventsMIME types
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
35
Research direction
Investigate the root cause of the inconsistent behavior where isDragReject returns true but onDrop accepts files. Review the referenced issues (#977, #25, #276) for similar reports. Focus on the components that handle drag events and MIME type detection in the react dropzone source code. Consider implementing the proposed isDragUnknown flag to provide better user feedback during ambiguous drag events.