fix: skip null drag entries during file upload (fixes #326644)

[vs-code-engineering]

Summary

TypeError: Cannot read properties of null (reading 'name') is thrown when dropping content onto the File Explorer that is not a file-system entry (e.g. dragged text, a URL, or non-file drag data). BrowserFileUpload.doUpload builds an entries array from DataTransferItem.webkitGetAsEntry(), but that DOM API returns FileSystemEntry | null — it returns null for items that do not represent a file. The local IWebkitDataTransferItem interface incorrectly declared the return type as non-nullable, so the null was pushed into an array typed as IWebkitDataTransferItemEntry[]. Later, the parallel upload callback reads entry.name (the factory frame in the stack) and crashes on the null element.

This is a type-contract violation: the interface lied about the return type, letting a null bypass the type system at the producer (the array-building loop), and the crash surfaced far downstream at entry.name.

Fixes #326644
Recommended reviewer: @bpasero

Culprit Commit

The masking type declaration (webkitGetAsEntry(): IWebkitDataTransferItemEntry) and the entries.push(item.webkitGetAsEntry()) producer are long-standing in fileImportExport.ts (the browser upload feature authored by @bpasero). No single recent commit introduced the null path; the telemetry recent-regression/stable-anomaly signals reflect a change in drop-input mix rather than a code change to this file. Most recent touch to the file was 7e8c7bef ("debt - reduce explicit any usage", @bpasero), which did not alter this behavior.

Code Flow

flowchart TD
    A[HTMLDivElement drop handler] --> B[ExplorerDelegate.drop]
    B --> C[BrowserFileUpload.upload -> withProgress]
    C --> D[doUpload: entries.push webkitGetAsEntry]
    D -->|API returns null for non-file item| E[null pushed into entries array]
    E --> F[Limiter.queue callback / factory]
    F --> G[read entry.name on null -> TypeError]

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Affected Files

• src/vs/workbench/contrib/files/browser/fileImportExport.ts — fix the IWebkitDataTransferItem.webkitGetAsEntry return type and skip null entries when building the upload list.

Repro Steps

1. Open a folder in VS Code (desktop or web).
2. Drag non-file content (e.g. selected text from a web page, or a URL) onto the File Explorer and drop it.
3. webkitGetAsEntry() returns null for that item; before the fix, doUpload pushed the null and later read entry.name, throwing TypeError: Cannot read properties of null (reading 'name').

How the Fix Works

Chosen approach (src/vs/workbench/contrib/files/browser/fileImportExport.ts):

• Corrected the IWebkitDataTransferItem.webkitGetAsEntry return type to IWebkitDataTransferItemEntry | null, matching the real DOM contract. This removes the type-system bypass that allowed null to enter a non-nullable array.
• In doUpload, the array-building loop now captures the result and only pushes it when it is non-null, so entries never contains a null. This fixes the bug at the data producer (where the invalid null is created) rather than guarding the crash site (entry.name), consistent with the fix-at-the-producer principle. No try/catch is added and no logService.error is touched.

After this change, the doUpload loop cannot place a null into entries, so the downstream entry.name read can no longer receive a null element.

Alternatives considered:

• Guarding entry.name at the crash site (line 166 / the factory callback) — rejected because it patches the symptom downstream and leaves the mistyped interface producing null for every other consumer.

Recommended Owner

@bpasero — original author of the browser file upload/import-export feature and most recent committer to this file.

Generated by errors-fix · 627.1 AIC · ⌖ 33.9 AIC · ⊞ 71K · ◷

[Copilot]

Pull request overview

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Updates drag-and-drop file import handling to account for webkitGetAsEntry() potentially returning null, preventing null entries from being processed downstream.

Changes:

• Updates IWebkitDataTransferItem.webkitGetAsEntry() type to return IWebkitDataTransferItemEntry | null.
• Filters out null entries when building the entries array, with clarifying inline comments.

[Copilot]

Pull request overview

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