SerialPort integration with WritableStream controller AbortSignal

Category: Device
Type: No developer-visible change
Status: Enabled by default (Chrome 100)
Intent stage: Shipped

Summary

This integration prevents a situation in which aborting a SerialPort's WritableStream can be blocked on 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.

Standards & signals

Specification: https://wicg.github.io/serial/#writable-attribute
Firefox: No signal — Firefox is opposed to the Web Serial API in general.
Safari: 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 been. Fixing the bug in the test exposed the need for this integration.
Tracking bug: https://bugs.chromium.org/p/chromium/issues/detail?id=1295963

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