android:defaultValue ignored when using PreferenceDataStore

[Mygod]

This is the decompiled Java code of Preference.dispatchSetInitialValue:

    private void dispatchSetInitialValue() {
        if(this.getPreferenceDataStore() != null) {
            this.onSetInitialValue(true, this.mDefaultValue);
        } else {
            boolean shouldPersist = this.shouldPersist();
            if(shouldPersist && this.getSharedPreferences().contains(this.mKey)) {
                this.onSetInitialValue(true, (Object)null);
            } else if(this.mDefaultValue != null) {
                this.onSetInitialValue(false, this.mDefaultValue);
            }

        }
    }

Unfortunately onSetInitialValue(true, defaultValue) doesn't work as expected. Also persisted attribute is ignored when data store is active. I wonder if there's a way to fix this in this library.

[gregkorossy]

What do you mean by "doesn't work as expected"?

Maybe the problems are related to this sentence in the documentation:

Once a put method is called it is full responsibility of the data store implementation to safely store the given values.

[Mygod]

Oh it means that the default value passed is discarded and no default value is set. For example, the implementation of onSetInitialValue usually looks like this: (taken from ListPreference)

    protected void onSetInitialValue(boolean restoreValue, Object defaultValue) {
        this.setValue(restoreValue?this.getPersistedString(this.mValue):(String)defaultValue);
    }

You see when restoreValue is true, defaultValue is discarded.

[gregkorossy]

Can't decide whether it's intentional or Google messed it up. Did you report it on the issue tracker?

[Mygod]

I reported but I'm too lazy to provide steps to reproduce for Google so they probably won't fix it.

Another evidence that it's Google messing it up, have a look at the signature of getPersistedString:

protected String getPersistedString(String defaultReturnValue);

Why would anyone pass this.mValue to defaultReturnValue?

[Mygod]

Reading the source code of androidx, I think this has been fixed.