Read preference on startup

#1

It seems that if a preference is changed by the user then after theia restart the change happens via event:

protected async initializeProviders(): Promise<void> {
    try {
        for (const scope of PreferenceScope.getScopes()) {
            const provider = this.providerProvider(scope);
            this.preferenceProviders.set(scope, provider);
            this.toDispose.push(provider.onDidPreferencesChanged(changes =>
                this.reconcilePreferences(changes)
            ));
            await provider.ready;
        }
        this._ready.resolve();
    } catch (e) {
        this._ready.reject(e);
    }
}

Question is what is the right way to read the correct value on theia startup as there a race condition between ready and change events.

[original thread by amiramw]

#2

I ran into this problem recently: https://github.com/eclipse-theia/theia/issues/7426

#3

There is a fix sketched out if you want to take a stab at it.

#4

otherwise, what are you trying to achieve? Maybe I can suggest a workaround, having looked at this code closely recently.

#5

[amiramw]

I have a flow on onStart that pulls a value from preference

#6

[amiramw]

Since preference providers update the preference on AbstractResourcePreferenceProvider.init there is a race condition

#7

[amiramw]

I wonder if this._ready.resolve() should not be after this.readPreferences() and then once the preference service is ready it will mean that all initial providers updated their values already

#8

I wonder if this._ready.resolve() should not be after this.readPreferences()

Yes it should (:-)), but unfortunately, that deadlocks because reading the preferences through an editor model reads preferences and that will wait for _ready() Hence my proposal to read preferences through a normal file read and only moving to a model when it’s needed.