Is it possible to new-configure `--ghc-options=-Wall` for a particular local package?

[lspitzner]

I just did the above and cabal decided to recompile the deps (which is a bit surprising on its own, but probably correct since deps might start breaking if they had -Werror as well..).

I gather that I can do

package mypackage
  ghc-options: -Wall

manually in cabal.project.local but that'll get overwritten by the next new-configure.

#4271 seems somewhat related.

[23Skidoo]

Hmm, I thought we already had a ticket for this, but I can't find it right now. @hvr, maybe you remember?

[lspitzner]

Now that i search again, I see #3883 and #4247. The only difference/addition that I spot is that this is about new-configure, i.e. about how flags translate to cabal.project.local, which is an aspect not mentioned in #3883.

[lspitzner]

(commandline-flags, not package flags)

[hvr]

It would indeed be convenient if we had a CLI syntax for new-configure to specify the scope of e.g. ghc-options for e.g. placing it into a specific package foo section. But I'm not sure how to design the UI for that, as e.g. --ghc-options foo:-Wall would require us to steal potential syntax from the GHC CLI...

[lspitzner]

perhaps just adding --PROG-options-global and --PROG-options-local (and perhaps defaulting/redirecting --PROG-options to the latter) is an acceptable solution? I don't see a straight-forward solution to something more fine-grained (per-package) either.

(perhaps: the --RTS/+RTS/-RTS style of cascading?

--package mypackage --package-specific-flag1 --package-specific-flag2 or
+package mypackage --package-specific-flag1 --package-specific-flag2 -package ?

but i don't want to have to parse that either, especially in combination with -- run-args that new-build should support..)

[23Skidoo]

Some ideas:

• --package foo --ghc-options -Wall
• --package-ghc-options foo=-Wall
• --package-foo-ghc-options -Wall

I haven't thought about which one of these would be easiest/hardest to implement.