IssueTracker

There's two issues here:

• android:defaultValue="@null" is actually treated as the defaultValue attribute not existing at all at runtime (we do still use it for Safe Args)
• We enforced every argument without a default value to be present in the URI/route, even if it was nullable.

While we can't fix the first one, we have made the change in Navigation 2.4.0-alpha09 to only check for default values for non-nullable parameters. This should mean that

1. Using android:defaultValue="@null" won't be a problem
2. Constructing a type in the Kotlin DSL via navArgument("argument_name") and making it nullable = true without a default value won't be a problem.

Unfortunately I still experience this bug with 2.4.0-alpha09 :(

java.lang.IllegalArgumentException: Deep link penny://app/offers can't be used to open destination Destination(de.penny.app.debug:id/offerListFragment) label=OfferListFragment class=de.penny.feature.offer.view.OfferListFragment.
    Following required arguments are missing: [sectionIndexOrName, raffleId]

This is the excerpt from my navigation graph XML:

<argument
    android:name="sectionIndexOrName"
    android:defaultValue="@null"
    app:argType="string"
    app:nullable="true" />

<argument
    android:name="raffleId"
    android:defaultValue="@null"
    app:argType="string"
    app:nullable="true" />

<deepLink
    android:id="@+id/offersDeeplink"
    app:uri="penny://app/offers" />

As you can see both parameters are nullable and have a default value of null.