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

[Michael Truog]

On 05/06/2018 11:34 PM, Ingela Andin wrote:
> Hi!
>
> 2018-05-04 14:40 GMT+02:00 Mahesh Paolini-Subramanya <mahesh@REDACTED <mailto:mahesh@REDACTED>>:
>
>     To echo Heinz's point, is there a *reason* for the deprecation?
>
>     Enquiring minds want to know...
>
>
> Th point is to phase out gen_fsm. The deprecated warning is important to get new users to choose gen_statem. Also if you have a living product you will probably be better of in the long run changing to gen_statem. This
> is not a complicated change and an exampel of how to do it is given in the gen_fsm manual page. Of course we give lots of time to adopt. We have no plan of removing the gen_fsm code swiftly, it is there in 20 and 21.
> I can see the deprecating process needs to enhanchend, and yes it sort of has more that one purpose which seems to conflict a bit.

One thing that might help is if we have the ability to deprecate types which I entered an entry for at https://bugs.erlang.org/browse/ERL-335 .  For example,  when all the time units switched from a format like milli_seconds to millisecond in Erlang/OTP 20.0 it would have been easier to have a deprecated type that can be used for an easier to understand warning.  That may seem like a small issue that can be avoided by switching to other functions or modules, but often changes don't need to be large for small changes that can be limited to type changes.

Best Regards,
Michael
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