[core v2] incorrect way to determine whether a response body is a stream or not

[jeremymeng]

Currently, when sending a request, if any of the operation response body mapper has Stream type, we consider the operation a streaming one, and set request.streamResponseBody to true.

azure-sdk-for-js/sdk/core/core-http/src/operationSpec.ts

Lines 98 to 111 in 2ae1fb8

	export function isStreamOperation(operationSpec: OperationSpec): boolean {
	let result = false;
	for (const statusCode in operationSpec.responses) {
	const operationResponse: OperationResponse = operationSpec.responses[statusCode];
	if (
	operationResponse.bodyMapper &&
	operationResponse.bodyMapper.type.name === MapperType.Stream
	) {
	result = true;
	break;
	}
	}
	return result;
	}

And we use the property request.streamResponseBody to determine the shape of the response after we receive the raw response from http layer.

• if the value is true, the body is stored in readableStreamBody (NodeJS.ReadableStream) for Node, or blobBody (Promise) for browser.
• if the value is false, the body is stored in bodyAsText (string)

The problem is that some responses of a streaming operation can have non-stream body. One example is the default mapper, which is often used to map error cases, can have text body type.

  responses: {
    200: {
      bodyMapper: {
        serializedName: "parsedResponse",
        type: {
          name: "Stream"
        }
      },
      headersMapper: Mappers.BlobDownloadHeaders
    },
    ...
    default: {
      bodyMapper: Mappers.StorageError,
      headersMapper: Mappers.BlobDownloadHeaders
    }
  },

The fix in PR #13192 uses the response status code to check the response type in the operation spec. However, in core v2, core-https is where we return the response and need to determine the shape of the response, while core-client is where we deal with operation specs. With this separation of responsibilities, we may need a different fix since we don't have access to operation specs in core-https.

[jeremymeng]

Fixed in #13192 too