feat: Allow large uploads via Blob

[AdrianCurtin]

Issue

Closes: #228

A Blob handed to createFile has no pipe, so it misses the streaming path added in #459 and is passed to PutObjectCommand whole. That materializes the entire file in memory, which is exactly what fails for uploads past the V8 buffer limit, the case #228 is about.

Picks up #229 by @dalyaidan1, which implemented this against the v2 SDK. @vahidalizad asked there for it to be redone on v3 after #221 landed, and it was never revisited. This is that rewrite, and it is much smaller now, because #459 already added the multipart upload path that the blob only needs routing into.

Approach

Anything exposing a web stream, a Blob or a File, is converted to a Readable before the params are built, so the existing Upload path carries it:

if (data && typeof data.stream === 'function' && typeof data.pipe !== 'function') {
  data = Readable.fromWeb(data.stream());
}

Duck typed on stream() rather than instanceof Blob, so a File, a blob from another realm, or a polyfill all work. The pipe check keeps a Node Readable on its existing path untouched.

The original PR built its own PassThrough and piped into it. That is no longer needed: Upload accepts a Readable directly and handles the multipart chunking, so this adds no plumbing of its own.

Behavior

• A Blob now streams to S3 in parts instead of being buffered, so memory use is bounded by the part size rather than by the file size.
• Buffer and string bodies are unchanged and still use PutObjectCommand.
• Node Readable bodies are unchanged.

Tests

spec/test.spec.js gains a blob uploads block: a blob takes the multipart path rather than PutObjectCommand, the upload is handed a Readable rather than the blob, the contents survive the conversion, and the source is not drained by the conversion itself, which is the property that makes an oversized file possible at all.

All four fail against the current implementation. Full suite passes.

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📥 Commits

Reviewing files that changed from the base of the PR and between b9245cb and dfc0558.

📒 Files selected for processing (2)

• index.js
• spec/test.spec.js

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