[erlang-questions] Erlang 21, Stability and the murder of an innocent Statemachine

[José Valim]

What about documentation from the OTP team that outlines a deprecation
policy? It may be a good opportunity to also outline other compatibility
guarantees, such as the compiled bytecode guarantees and the node
compatibility guarantees, if such are not yet documented.

We did define such document not long ago for Elixir. In terms of
deprecations, we have two terms: "soft-deprecation" and "hard-deprecation".
The soft-deprecation is added as soon as a new implementation exists. At
this point we don't emit any warnings, but we do update the docs to say the
feature will warn in the future and start to point folks towards better
ways.

A hard-deprecation is when we finally start emitting warnings. A
hard-deprecation can only be added after an alternative exists for at least
2 Elixir releases. This is very important because it means that, once a
feature is hard deprecated, you know you can use the proposed alternative
and that alternative is supported at least two versions back.

This is only necessary if a feature is being replaced. In case a feature is
being removed, such as non-smp VM versions, you may skip directly to the
"hard-deprecation" and emit warnings straight-away since there won’t be an
alternative in the future anyway.

I am not proposing for Erlang/OTP team to follow those rules and
conventions but writing *some* rules as minimum guarantees may improve
communication and help the community plan in terms of warnings,
deprecations and removals accordingly. I would just avoid emitting
deprecation warnings in the same version that an alternative is introduced,
because it means library developers need to either only support the latest
version or introduce conditionals (either at compile-time or runtime) to
support multiple versions.

*José Valimwww.plataformatec.com.br
<http://www.plataformatec.com.br/>Founder and Director of R&D*

-- 


*José Valimwww.plataformatec.com.br
<http://www.plataformatec.com.br/>Founder and Director of R&D*
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://erlang.org/pipermail/erlang-questions/attachments/20180507/d3018d81/attachment.htm>