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Recoverable read errors #230

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Recoverable read errors #230

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d7525b5
New types for stopbits and databits
MitchBradley Dec 18, 2025
cad84f3
readLoop retries on recoverable errors instead of failing
MitchBradley Dec 19, 2025
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63 changes: 44 additions & 19 deletions src/webserial.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -22,13 +22,13 @@ export interface SerialOptions {
* The number of data bits per frame. Either 7 or 8.
* @type {number | undefined}
*/
dataBits?: number | undefined;
dataBits?: 7 | 8 | undefined;

/**
* The number of stop bits at the end of a frame. Either 1 or 2.
* @type {number | undefined}
*/
stopBits?: number | undefined;
stopBits?: 1 | 2 | undefined;

/**
* The parity mode: none, even or odd
Expand Down Expand Up @@ -210,30 +210,55 @@ class Transport {
* Read from serial device and append to buffer
*/
async readLoop() {
this.reader = this.device.readable?.getReader();
if (!this.reader) {
throw new Error("Reader not found");
}
try {
let stillReading = true;
while (stillReading) {
while (this.device.readable) {
this.reader = this.device.readable?.getReader();
try {
const { value, done } = await this.reader.read();
if (done) {
this.reader.releaseLock();
stillReading = false;
this.trace(`Serial port done`);
break;
}
if (!value || value.length === 0) {
continue;
// The following test is purely precautionary because .read()
// is not supposed to return empty data when done is false
if (value && value.length) {
const newValue = Uint8Array.from(value);
this.buffer = this.appendArray(this.buffer, newValue);
}
} catch (error) {
if (error instanceof Error) {
// Read retry is possible for the following errors
const nonFatal = [
"BufferOverrunError",
"FramingError",
"BreakError",
"ParityError"
];
if (nonFatal.includes(error.name)) {
this.trace(`Recoverable serial port error: ${error.message}`);
continue;
}
// Otherwise the read loop cannot continue
this.trace(`Unrecoverable serial port error: ${error.message}`);
break;
}
const newValue = Uint8Array.from(value);
this.buffer = this.appendArray(this.buffer, newValue);
if (error instanceof DOMException) {
// The read loop cannot continue after a DOMException error
if (this.onDeviceLostCallback) {
this.onDeviceLostCallback();
} else {
this.trace(`Unrecoverable serial port error: ${error.message}`);
}
break;
}
// The read loop cannot continue after an error whose class is unknown
this.trace(`Unrecoverable serial port error: ${error}`);
break;
} finally {
this.reader.releaseLock();
}
} catch (error) {
this.trace(`Error reading from serial port: ${error}`);
} finally {
this.reader = undefined;
}
// Fatal error or serial port stream ended
this.trace(`readLoop exited`);
}

flushInput() {
Expand Down