[Bug 23772] New: Just return read result when there's data synchronously readable

https://www.w3.org/Bugs/Public/show_bug.cgi?id=23772

            Bug ID: 23772
           Summary: Just return read result when there's data
                    synchronously readable
           Product: WebAppsWG
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Streams API
          Assignee: tyoshino@google.com
          Reporter: tyoshino@google.com
        QA Contact: public-webapps-bugzilla@w3.org
                CC: mike@w3.org, public-webapps@w3.org

It's currently implemented in preview ver.
https://dvcs.w3.org/hg/streams-api/raw-file/tip/preview.html

ByteStreamReadResult.data is a Promise when no data synchronously readable.
Otherwise, data is actual data.

This is inspired by e.g. Chrome's network stack code (ERR_IO_PENDING).

----

It's efficient, but I got feedback against this from Elliott. Quoting.

- It's really weird that sometimes this thing is a Promise and sometimes it
isn't.
- It also doesn't make sense that the data property is a Promise since the size
and eof properties cannot be known until the promise is resolved so we might as
well return Promise<Result> instead of a Result with a Promise property and a
size/eof property external to it.
- Having the value jump between Promise and real data based on network latency
is going to be very error prone for authors, you can probably write your code
all one way if your network is fast and then see it fail when sometimes it's
slower.
- I'd suggest always returning a Promise and dealing with it at microtask time
for the "synchronous" case.

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Received on Friday, 8 November 2013 08:21:59 UTC