Add nullability annotations

[freya022]

No description provided.

[felldo]

I think it's better to add a dependency on compileOnly("org.jspecify:jspecify:0.3.0").
It is pretty widely supported and saves us pretty much all annotations. While in your case you could use @ParametersAreNonnullByDefault on the package-info file, it doesn't help with return types and afaik it is not possible to mark generic parameters an non null.

Therefore I suggest to add the mentioned dependency instead and add a package-info.java file which contains the following:

@NullMarked
package net.fellbaum.jemoji;

import org.jspecify.annotations.NullMarked;

With this all types should be declared a NonNull if not otherwise marked as Nullable

[freya022]

I don't like implicit non-null, I'd rather have either NotNull/Nonnull, or Nullable on the returned types and parameters.

As for generic types, they are supported by annotations with TYPE_PARAMETER or TYPE_USE targets.
The JetBrains annotations do support it, but the java compiler has a bug which makes annotations satisfying more than 1 scope, be duplicated in the javadocs, which is why I am not using it here

[freya022]

At least jspecify annotations works with Kotlin so, alright, but it's quite weird how you can use them on generics, but they are still seen as platform types. Though using @NullMarked on the package does help for generics too

[freya022]

Last question though: Do we keep the dependency compileOnly? When looking at the sources, the annotation is not present in the classpath, and so, creates errors.

I think adding a 3 KB dependency isn't too much

[felldo]

I don't like implicit non-null, I'd rather have either NotNull/Nonnull, or Nullable on the returned types and parameters.

I don't really agree with you on that, but imo null annotations can clutter the code quite a bit in a language thats already very verbose. This is a completely null free library and if a null value is returned, it is a bug. For that reason I don't think it is a big deal to just specify that everything returns NonNull in the package info.
Btw. why did you add a @Nullable to the parameters? Even if the null case is handled, it is not really a "valid" argument to pass as you will never get something different than an empty string/collection/optional an therefore shouldn't be Nullable.

Last question though: Do we keep the dependency compileOnly? When looking at the sources, the annotation is not present in the classpath, and so, creates errors.

I think adding a 3 KB dependency isn't too much

For that case I think we can add the dependency as compileOnlyApi though I am not 100% sure if this is the right thing to do. You can test if it resolves this issue, otherwise I would keep it as compileOnly.

[freya022]

Issues solved

[felldo]

LGTM! Thanks.