[feature request] 'deprecated' flag

[kit-ty-kate]

A builtin support in opam for a deprecated flag would be nice. Here what such flag would do:

• Any packages flagged with deprecated would be avoided by the solver unless there is no other choice (e.g. some user wants to install package a which depends on b which is deprecated)
• If it is installed, show up a note after installation notifying the user that the package is deprecated. If the developer deprecating the package wants to add precisions, they can do it using the post-messages field as it was already done for such a purpose.

Related to ocurrent/opam-health-check#8

[dbuenzli]

Related to #2046

[AltGr]

There is a significant overlap with hidden-version (which we haven't renamed yet it seems ?) here;

[dra27]

I think it would implemented internally as hidden-version - the difference is just the extra messages, I think?

[kit-ty-kate]

Implemented in #4523

I think it would implemented internally as hidden-version - the difference is just the extra messages, I think?

The differences are:

• the name: which is going to be used by external tools (e.g. opam-health-check). For that purpose only we most likely want to differenciate the two.
• upgrades of a deprecated package is not forbidden as it is with hidden-version
• the extra message