widen blob payload input types, add blob payload output converter

[kuhe]

aws/aws-sdk-js-v3#4786
aws/aws-sdk-js-v3#4265

Blob types enhancements

• on the client input side, operation input members with type blob and trait HttpPayload have been widened from Uint8Array to BlobTypes, which contains common and runtime specific types.

export type BlobTypes = string | ArrayBuffer | ArrayBufferView | Uint8Array | RuntimeBlobTypes;

// example Node.js runtime additions
export type RuntimeBlobTypes = Readable | Buffer;
// browser additions
export type RuntimeBlobTypes = Blob | ReadableStream;

• on the client output side, operation output members with type blob and trait HttpPayload have been wrapped in Uint8ArrayBlobAdapter, which extends the Uint8Array native class and adds a convenient platform-specific way to convert to string. Example in the linked JSv3 PR feat(clients): automatic blob type conversions aws/aws-sdk-js-v3#4836.

---

This applies in general, but the user story is difficulty/inconvenience around non-streaming blob i/o, e.g. in Lambda invoke. Non-streaming blobs were treated uniformly as Uint8Array in input and output, but this does not cover the realistic use cases of payload blobs.

const lambda = new Lambda({
  region: "us-west-2",
});

const invoke = lambda.invoke({
  FunctionName: "echo",
  Payload: JSON.stringify({
    hello: "world",
  }), // without input widening, this would be a type error since string is not Uint8Array.
});

const payload = (await invoke).Payload;

console.log(JSON.parse(payload?.transformToString() ?? "{}")); // adapter adds the string conversion method, preserves the type extending Uint8Array.

• JSv3 will write an e2e integration test suite for this.

[milesziemer]

Do we need this whole method if it just imports something? Or maybe change the name?

[kuhe]

I rolled it into the generateCollectBodyString method, which is called in all places that generateCollectBody was called.