@tus/s3-store: complete empty multipart uploads on create

[hsusul]

Problem

@tus/server treats Upload-Length: 0 as immediately final and calls onUploadFinish without write() (PostHandler sets isFinal when size === 0 && !sizeIsDeferred).

S3Store.create only starts a multipart upload and writes the .info object. Consumers that HeadObject / getObject the key in onUploadFinish (e.g. Supabase Storage) then see a bare 404 because the multipart was never completed.

finishMultipartUpload already handles empty parts by uploading a zero-byte part — it just was not reached on the create-only path.

Reported downstream: supabase/storage#1300
(Supabase maintainer asked to fix upstream: supabase/storage#1365 (comment))

Fix

When upload.size === 0 && !upload.sizeIsDeferred, complete the empty multipart in create, then completeMetadata and clear cache — same sequence as the end of write().

Update the existing zero-byte integration test to match server behavior (create only; no write()).

Test plan

• Adjusted should successfully upload a zero byte file to assert object exists after create alone
• CI for @tus/s3-store

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[changeset-bot]

🦋 Changeset detected

Latest commit: 3d511f7

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@tus/s3-store	Patch

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[devin-ai-integration]

Devin Review found 1 potential issue.

[devin-ai-integration]

🟡 Empty creation requests now fail

With zero length and creation-with-upload, create completes the upload before the server invokes write. The valid request then fails because its upload is already closed.

Prompt for agents

Preserve valid creation-with-upload requests whose Upload-Length is zero. PostHandler always calls DataStore.write when the POST carries application/offset+octet-stream, but S3Store.create now completes the multipart upload first. The subsequent S3Store.write calls retrieveParts and receives NoSuchUpload. Coordinate the server and store behavior, or make the S3 store's zero-byte completion idempotent, so both create-only empty uploads and empty creation-with-upload requests succeed. Add coverage for a zero-length POST carrying the creation-with-upload content type.

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[hsusul]

Good catch — creation-with-upload does call write() after create even when Upload-Length is 0.

Addressed by making write idempotent: if retrieveParts returns NoSuchUpload and offset === size, drain the body and return the final offset. Added a regression test for zero-byte creation-with-upload.