fix(web): keep folder drops out of attachment uploads

[StiensWout]

Dropping a folder creates a failed attachment and blocks Send. Filter directory entries in the shared workspace drop handler before they reach the uploader. Mixed drops still attach real files, and a folder drop explains how to reference an accessible path.

Fixes #11961.

The same handler covers chat, sidebar thread rows, sidebar search results, and the legacy sidebar on web and desktop. Files without MIME types and drops without entry metadata keep working.

Verification

• Nine focused drop-handler tests pass. Three new cases failed against the original behavior before the fix.
• Web typecheck, targeted lint, formatting, and git diff --check pass.
• Chromium 154, real filesystem folder and text file dropped through Input.dispatchDragEvent, against an isolated T3 server:

Drop	Before	After
Folder + text file	Directory upload fails with ERR_FILE_NOT_FOUND; Send disabled	Only the text file uploads, HTTP 204; no failed attachment; Send enabled
Folder only, with an existing draft	Creates a failed attachment	Zero upload requests; composer contents unchanged; Send enabled

Browser inspection confirmed isDirectory: true for the folder and false for the text file. Desktop uses the same handler; a packaged desktop build was not separately exercised.

Before

After

_{Prepared for Wout by gpt-6 in Codex through T3 Code.}

Summary by CodeRabbit

• Bug Fixes
  • Improved drag-and-drop file handling in chat workspaces.
  • Folders are now rejected with an informational notification instead of being attached.
  • Mixed drops attach only valid files, including files without a MIME type.
  • Files remain supported when drag metadata is unavailable.
  • Rejected folders are no longer recovered through fallback file data.

[macroscopeapp]

Approvability

Verdict: Approved at cdc4657

Macroscope's review found this PR approvable — This is a focused bug fix that prevents folder entries from reaching attachment uploads while preserving normal and mixed file drops. The shared handler change is covered by targeted tests and introduces no schema, security, deployment, default-setting, or static-analysis configuration changes.

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[macroscopeapp]

All clear

^{Posted via Macroscope — Effect Service Conventions}

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 53612cc and cdc4657.

📒 Files selected for processing (2)

• apps/web/src/components/chat/workspaceFileDrop.test.ts
• apps/web/src/components/chat/workspaceFileDrop.ts

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📝 Walkthrough

Walkthrough

The workspace drop handler now inspects drag items, rejects folders, preserves valid files, and reports skipped folders. Tests cover mixed drops, MIME-less files, missing entry metadata, and fallback behavior.

Changes

Workspace Drop Filtering

Layer / File(s)	Summary
Drop item contract apps/web/src/components/chat/workspaceFileDrop.ts	WorkspaceFileDragEvent now optionally exposes drag items with file retrieval and directory metadata.
Drop filtering and validation apps/web/src/components/chat/workspaceFileDrop.ts, apps/web/src/components/chat/workspaceFileDrop.test.ts	onDrop skips directory entries, collects valid files, shows an informational toast when folders are skipped, and avoids adding an empty file collection. Tests cover mixed drops, MIME-less files, missing entry metadata, and fallback behavior.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix · Severity of issue fixed: Low

Merge Risk: ⚪ Minimal · up to cdc46

The folder filtering behavior preserves valid file drops and does not reattach rejected folders through the fallback path. No actionable merge-blocking risk remains.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 2 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the primary change: preventing folder drops from becoming attachment uploads.
Description check	✅ Passed	The description explains what changed, why it changed, affected surfaces, verification results, and UI behavior with before-and-after screenshots. It does not include the template's Checklist section,…
Linked Issues check	✅ Passed	The PR addresses the coding requirements in #11961. workspaceFileDrop.ts reads dataTransfer.items, skips entries whose webkitGetAsEntry().isDirectory is true, and does not call addFiles for fo…
Out of Scope Changes check	✅ Passed	The changes are limited to the shared workspace drop handler and its automated tests. The toast, filtering logic, fallback behavior, and test updates directly support #11961. No unrelated product beha…

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✨ Finishing Touches

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[StiensWout]

Reviewed the non-blocking docstring-coverage warning. The changed handler has a nearby comment explaining why directory metadata must be read synchronously during the drop event. Extra docstrings for this existing handler and its test helper would repeat the code; the repository's guidance favors comments that explain behavior or constraints. No code change is needed for that warning.

_{gpt-6 via Codex through T3 Code, responding for Wout.}

[juliusmarminge]

Superseded by #12001, which already fixed #11961 and merged to main. Closing this PR as leftover hygiene.

[juliusmarminge]

Superseded by #12001, which already landed the folder-drop fix for #11961 (path chips on local, refused on remote). Closing this PR as superseded.