Hook redesign

[ezyang]

@ttuegel, let's make this a tracking ticket for hook redesign.

I'm collecting tickets of things that should be fixed in the redesign:

• Get LocalBuildInfo in pre-test hook #2599 - We should make LBI uniformly available to all hooks when it is available
• LocalBuildInfo should change at build time when components are selected #2910 - Hooks should operate on per-component level
• Proposal for a Cabal plugin API (inversion of control) #2395 - This was a proposal to invert control to external processes, so that you could add hooks without requiring a build against a version of Cabal
• Lessons learned from Custom #3065 - I wrote up some lessons I had learned from Custom
• install hook (Custom setup) is not called on Setup copy/register #1805 - install hook is redundant with copy/register hook
• localPkgDescr is frequently out-of-date #3606 - only the configure pre-hook should return a HookedLocalBuildInfo; the rest should not!
• Way to pass custom options to hook script #3625 - no way to pass custom arguments to hooks
• Revert Revert "Generalize HookedBuildInfo to work with any type of component." #3627 - HookedBuildInfo should support all different component types, not just library and executable

[dcoutts]

And remove things like the program db in some of the flag types which are there only to avoid modifying the hook function types. See the TODO in the code.

[fmaste]

Now with #3670 we can add a hook to generate the autogen-modules. The hook output could be Just Text and its input the PackageDescription and which component to build. It defaults to create the Paths_* module or else returns Nothing so others can be built with a different hook.

With this it would be possible to override the Paths_* module and generate modules on the fly without having to guess where to put them (dist/build, dist/build/exe, dist/libbuild, etc) or when to create them (on configure, on build, before cpp, etc).

[ezyang]

@fmaste, do you want to make a ticket describing this suggestion in more detail (like a spec), and then edit the description here to link to it?

[ezyang]

Sorry, I don't think this is going to happen for 2.0.

[andreabedini]

@Mikolaj @sheaf Do you think this can be closed after the implementation of #9292?

[Mikolaj]

I guess so? @mpickering, @sheaf, @ezyang, @ttuegel, are there any morsels of ancient wisdom still to be found here? What about the tickets listed in the description? Can some of them be closed and the remaining ones refreshed?

[Mikolaj]

Thank you for you work, everybody. Closing.