Deprecate whereNotNull() and add nonNulls to follow Dart's naming conventions on the Iterable

[vincevargadev]

Dart has a nonNulls static extension method on the Iterable.

The collection package also deprecated whereNotNull and asks users to use nonNulls.

It would be great if the same name could be used on Streams with rxdart.

[hoc081098]

I think we should keep whereNotNull:

• stream_transform pkg is using the name whereNotNull (https://pub.dev/documentation/stream_transform/2.1.1/stream_transform/WhereNotNull/whereNotNull.html).

• RxDart prefers methods over getters:

Stream.fromIterable([1, 2, 3, null, 4])
    .whereNotNull()
    .where((i) => i.isEven)
    .switchMap(...)
    .listen(...)

compared to

Stream.fromIterable([1, 2, 3, null, 4])
    .nonNulls
    .where((i) => i.isEven)
    .switchMap(...)
    .listen(...)

• In Dart, where is used similarly to filter in other languages (e.g., Kotlin).
  In Kotlin, there is filterNotNull() (https://kotlinlang.org/api/core/kotlin-stdlib/kotlin.collections/filter-not-null.html, https://kotlinlang.org/api/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines.flow/filter-not-null.html), so I think whereNotNull() is analogous to filterNotNull() in other languages.

What do you think?

[vincevargadev]

I totally get what you are saying. I wouldn't have named Dart's non-null filter nonNulls myself, but it is what it is, it is what it is called in the Dart programming language. For what it's worth, I preferred whereNotNull, too.

However, working with rxdart is a pleasure mainly because it integrates so well with Dart and the Dart ecosystem. The method names, where an equivalent method exists, follow the same conventions as Dart's core data structures, so if an iterable-like data structure is replaced with a stream, updating the code is super easy, barely an inconvenience.

Now, when working with streams and iterables, I always need to keep in mind which one I'm using, and I need to remember that streams and iterables have different methods/getters to filter out null values.

Giving this issue the title Replace whereNotNull() with nonNulls was incorrect on my part, in my opinion, rxdart should follow what Dart and the collection package is doing:

• Keep whereNotNull() but deprecate it.
• Add nonNulls as preferred.

This will keep old code working and also allow users update when they can with a very small update (it's basically find all and replace).

I updated the title to capture better what my suggestion is: Deprecate whereNotNull() and add nonNulls to follow Dart's naming conventions on the Iterable.

Another approach could be to have both, and let users pick which they like more, though I'm not sure that's a great idea.