A peek at the roadmap for pattern matching and more

[Eddie Aftandilian]

On Fri, Aug 14, 2020 at 1:18 PM Brian Goetz <brian.goetz at oracle.com> wrote:

>
> >
> > Inside Google we have enabled the `-parameters` attribute by default
> > and have an Error Prone check that simulates named parameters
> > (https://errorprone.info/bugpattern/ParameterName).
> >
> > Initially we had it enabled as a compilation error.  We believed that
> > renames of parameters happened infrequently and rarely crossed
> > compilation boundaries.  We found that those renames were more
> > frequent than expected, and there were a number of accidental breaking
> > changes to core libraries like Guava that caused breakage at a
> > distance.  We ended up demoting the check to a warning.  The general
> > feeling was that this was mostly a problem for core libraries and not
> > typical application code.  One proposal was to leave it as an error by
> > default, but to allow core libraries to opt out of publishing their
> > parameter names.
> >
> > All that said, I don't think this is a problem for records since the
> > names there are clearly part of the API.
>
> Thanks for enhancing the theoretical discussion with actual data!
>

Happy to help :)


> The part of this that really interests me is the "boundary-crossing"
> one.  Within a maintenance boundary (package, module, multi-module
> project, monorepo, depending on your tooling) you are free to rename at
> will, using suitable refactoring tools, since you can find all the
> clients and fix them.  It only becomes a real problem when references
> cross boundaries.
>
> I'm curious what's behind your intuition about why records would be
> immune (not that I disagree.)  Is it that they are right there in the
> header?  That they are so restricted that users can't lose sight of the
> fact that they are special?
>

I think it's the same reasoning you stated in one of the messages earlier
in this thread: "the name of a component in records flows into constructor
descriptors, accessor names, etc."  Changing the name of a record component
seems to obviously be a breaking change in that it affects especially the
accessor names.
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