Question about cancellation during buildDocument

[ydaveluy]

Hello,

When I edit a big document (300 000 lines) with my dsl it takes around 3.3s to build (from parsing to validation). I noticed that the cancellation of the previous build happen very late in case of multiple editions.

I instrumented the builder this way:

  protected override async buildDocuments(documents: LangiumDocument[], options: BuildOptions, cancelToken: Cancellation.CancellationToken): Promise<void> {
        try {
            console.time('buildDocuments');
            await super.buildDocuments(documents, options, cancelToken);
        }
        catch (e) {
            console.log('exception');
            throw e;
        }
        finally {
            console.timeEnd('buildDocuments');
        }
    }

If I append 10 characters in my file, one each 0.3 second (approximately), I have the following log:

exception
buildDocuments: 2.634s
exception
buildDocuments: 2.446s
exception
buildDocuments: 2.398s
exception
buildDocuments: 2.431s
exception
buildDocuments: 2.729s
exception
buildDocuments: 2.329s
exception
buildDocuments: 2.369s
exception
buildDocuments: 2.408s
exception
buildDocuments: 2.727s
buildDocuments: 3.351s

The exception raised by the CancellationToken happen after around 2.5s.

I tried to reduce the interruptionPeriod with setInterruptionPeriod but it didn't changed anything.

In such case the final document is built after more than 20s after the last edition.
Is there a way to interrupt the build quickly ?

[msujew]

Hey @ydaveluy,

Unfortunately, the first step in the document building pipeline is always parsing which is usually synchronous and therefore cannot be interrupted.

We built the AsyncParser for this, but it's not ideal. It has a fairly slow startup time, but you might want to use it anyway. See here on how to use it.