fix(fetch-http-handler): check for null fetch response.body

[kuhe]

Issue

#4398
#4369

Description

Add null check for fetch API response.body.

Testing

• add unit test
• manual testing with Chrome Version 113.0.5672.63 (Official Build) (x86_64)

Workaround

For affected users' clients, you can apply a code workaround until such time that you upgrade to a version of the AWS SDK for JavaScript v3 that contains this fix.

    import { S3 } from "@aws-sdk/client-s3";
    
    const s3 = new S3({
      credentials,
    });

    // this example is on an S3 client. The middlewareStack property is available on all clients.
    // add this middleware to default a fetch response body to an empty Uint8Array, 
    // before making any requests.
    s3.middlewareStack.addRelativeTo(
      (next) => async (args) => {
        const { response } = await next(args);
        if (response.body == null) {
          response.body = new Uint8Array();
        }
        return {
          response,
        };
      },
      {
        name: "nullFetchResponseBodyMiddleware",
        toMiddleware: "deserializerMiddleware",
        relation: "after",
        step: "deserialize",
        override: true,
      }
    );

Additional context

In the API spec for fetch's Response::body https://developer.mozilla.org/en-US/docs/Web/API/Response/body,
the body is supposed to be null for responses that have an empty body.

A note clarifies that this did not happen in browser implementations

Note: Current browsers don't actually conform to the spec requirement to set the body property to null for responses with no body (for example, responses to HEAD requests, or 204 No Content responses).

but with the latest version of Chrome, and possibly other browsers, the spec is now apparently being adhered to. This null check should have been in place originally, but is now necessary.

[cezarderevlean]

Thank you for providing the workaround.

[LorhanSohaky]

When will the fix be made available? @kuhe

[jroru]

@LorhanSohaky Looks like it was included in the v3.329.0 release

[github-actions]

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