Intent to Prototype and Ship: SerialPort integration with WritableStream controller AbortSignal
Reilly Grant
Contact emails
Specification
https://wicg.github.io/serial/#writable-attribute
https://github.com/WICG/serial/pull/160
Summary
This integration prevents a situation in which aborting a SerialPort's WritableStream can be blocked waiting for a partially-written chunk of data to be written to the port. If the port is waiting for the peer device to provide a flow control signal it could be blocked indefinitely. The intent of aborting a WritableStream is to immediately stop trying to write data to the underlying sink. The introduction of an AbortSignal to the controller was done to fix bugs like this.
Blink component
TAG review
The Web Serial API and WritableStream controller AbortSignal have both been reviewed by the TAG.
TAG review status
Not applicable
Risks
Interoperability and Compatibility
This integration introduces a minor change to the behavior of a SerialPort's WritableStream because it means that it no longer waits for the current write() operation to complete. However, since the intention of abort() is to discard queued writes and the exact timing for when the current write() operation completes depends on how quickly data is being transmitted by the port, the current behavior is more appropriately classified as a bug than a feature. It would be very hard for developers to rely on the previous buggy behavior, and so we believe the compat risk to be minimal.
Gecko: No signal
Firefox is opposed to the Web Serial API in general.
WebKit: No signal
Safari is opposed to the Web Serial API in general.
Web developers: No signals
I don't believe any developers have noticed this particular quirk. I noticed because I was debugging a test of the abort() behavior that passed even though there was a write() pending and without this integration it shouldn't have. Fixing the bug in the test exposed the need for this integration.
Other signals:
Debuggability
SerialPort and WritableStream are JavaScript APIs which can be debugged using DevTools.
Is this feature fully tested by web-platform-tests?
Yes
Flag name
None
Requires code in //chrome?
False
Tracking bug
https://bugs.chromium.org/p/chromium/issues/detail?id=1295963
Estimated milestones
M-100
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/4778232531386368
This intent message was generated by Chrome Platform Status.
Mike Taylor
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chrishtr via Chromestatus
mkwst via Chromestatus
Reilly Grant
LGTM3
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