I generally assume the other way around. Many (most) libraries don't
annotate the return values of their methods, so I assume everything is
nullable unless specifically told otherwise. I would prefer everything be
non-nullable unless specifically stated (the ? is the one thing I would
steal from typescript if I could), but given that library code can't be
modified to be explicit when null return values are possible, I don't think
we can make that assumption.
Mike
On Thu, May 22, 2025 at 10:57 AM Dmitri Bourlatchkov <di...@apache.org>
wrote:
> My preference is for option 1 below.
>
> On Thu, May 22, 2025 at 1:53 PM Alex Dutra <alex.du...@dremio.com.invalid>
> wrote:
>
> > Hi,
> >
> > My proposal was centered around compile-time checks and targets mostly
> > developers and contributors. I am not questioning the usefulness of
> > runtime checks when these make sense.
> >
> > Maybe an example is better than a thousand words. Let's imagine a
> > simple getOrDefault() method. Which version do you prefer?
> >
> > 1. Annotate only nullable items:
> > public String getOrDefault(@Nullable String s, String def) { return s
> > == null ? def : Objects.requireNonNull(def); }
> >
> > 2. Annotate only non-null items:
> > @Nonnull public String getOrDefault(String s, @Nonnull String def) {
> > return s == null ? def : Objects.requireNonNull(def); }
> >
> > 3. Annotate everything:
> > @Nonnull public String getOrDefault(@Nullable String s, @Nonnull
> > String def) { return s == null ? def : Objects.requireNonNull(def); }
> >
> > Many places in Polaris are using option 3, which is too verbose and
> > leads to visual fatigue. What I was suggesting to the community is to
> > adopt option 1, that reduces the visual clutter and also assumes
> > non-null by default.
> >
> > (You will notice that I added a runtime check to all three versions.)
> >
> > Hope that helps to clarify the discussion.
> >
> > Alex
> >
> > On Wed, May 21, 2025 at 8:54 PM Yufei Gu <flyrain...@gmail.com> wrote:
> > >
> > > >
> > > > In my opinion, assuming everything is nullable by default isn't the
> > > > best approach for writing robust code. I believe a bias towards
> > > > non-nullness leads to more reliable systems.
> > >
> > > I agreed with the intention, but am concerned that assuming everything
> is
> > > non-nullness may discourage null-checking, which is problematic as
> > runtime
> > > null-checking isn't a thing.
> > >
> > > Yufei
> > >
> > >
> > > On Wed, May 21, 2025 at 9:52 AM Alex Dutra
> <alex.du...@dremio.com.invalid
> > >
> > > wrote:
> > >
> > > > Hi Eric,
> > > >
> > > > You're right that annotations don't change the bytecode at runtime.
> > > > Their real value comes during compilation, as many static analysis
> > > > tools use them to flag potential issues. They can even cause build
> > > > failures depending on how you configure them. My IDE (IntelliJ)
> > > > frequently warns me when I forget to handle a potential NPE; if
> you're
> > > > not seeing similar feedback, it might be worth checking your IDE
> > > > settings.
> > > >
> > > > While the annotations are primarily for compile-time checks, that
> > > > doesn't mean we can't also incorporate runtime checks. We should aim
> > > > to include these whenever this makes sense, for example by using
> > > > Guava's Preconditions. This is especially useful if we can't
> guarantee
> > > > that a method parameter, for instance, will never be null, because
> > > > it's being provided by some external system.
> > > >
> > > > In my opinion, assuming everything is nullable by default isn't the
> > > > best approach for writing robust code. I believe a bias towards
> > > > non-nullness leads to more reliable systems.
> > > >
> > > > I am also a big fan of Optional and think we should strive to use it
> > > > as much as possible. That said, it's not always possible, especially
> > > > if you are implementing a third-party interface that doesn't use it.
> > > > Using Optional in class fields and method parameters is also
> > > > controversial: Optional was designed primarily as a signal from the
> > > > callee to the caller, to signify: "no result". In other words, its
> > > > main purpose is to clarify method return types. This post on Stack
> > > > Overflow by Brian Goetz is worth reading: [1].
> > > >
> > > > Thanks,
> > > >
> > > > Alex
> > > >
> > > > [1]:
> > > >
> >
> https://stackoverflow.com/questions/26327957/should-java-8-getters-return-optional-type/26328555#26328555
> > > >
> > > >
> > > > On Wed, May 21, 2025 at 4:37 PM Eric Maynard <
> eric.w.mayn...@gmail.com
> > >
> > > > wrote:
> > > > >
> > > > > Thanks for bringing this up as I’ve been confused by this a few
> > times.
> > > > >
> > > > > Before Polaris I hadn’t really encountered these annotations and I
> > was
> > > > > surprised to learn they don’t “do anything” — that is, there is no
> > > > > additional safety you get at runtime when a null value is passed
> > into a
> > > > > parameter marked non-null. Similarly nothing enforces that you
> handle
> > > > null
> > > > > values when something is annotated as nullable.
> > > > >
> > > > > For that reason, I tend to assume everything is nullable regardless
> > of
> > > > > annotation and I would be in favor of standardizing around that
> > > > assumption.
> > > > > Iff something is annotated as Non-null a developer should feel safe
> > > > > skipping a check for null, but otherwise they should handle null.
> > > > >
> > > > > I am a big fan of Optional and of trying to reduce the usage of
> null
> > as
> > > > > much as possible though.
> > > > >
> > > > > On Wed, May 21, 2025 at 3:02 PM Alex Dutra
> > <alex.du...@dremio.com.invalid
> > > > >
> > > > > wrote:
> > > > >
> > > > > > Hi all,
> > > > > >
> > > > > > A while ago, we had a discussion regarding which nullness
> > annotations
> > > > > > to use and whether we should consider favoring non-null by
> > default. I
> > > > > > would like to revive that discussion.
> > > > > >
> > > > > > We are currently using the `jakarta.annotation` package
> > consistently,
> > > > > > but the defaults are not clear: should we consider everything as
> > > > > > non-null by default and only annotate the nullable things, or the
> > > > > > other way around? Some classes are cluttered with both
> annotations,
> > > > > > which seems unnecessary and confusing.
> > > > > >
> > > > > > I would personally be in favor of considering everything as
> > non-null by
> > > > > > default.
> > > > > >
> > > > > > Please let me know your thoughts.
> > > > > >
> > > > > > Alex
> > > > > >
> > > >
> >
>
