Allow allow-newer in cabal.project package stanzas

[bgamari]

Describe the bug
Currently allow-newer can be used to lift lower-bounds on a set of packages throughout the install plan. However, this is often a far larger hammer than is necessary. More often, I merely need to lift an outdated bound in a particular package. cabal-install should allow the user to express this intent in their cabal.project file with use of the allow-newer field in a package stanza. For instance, if package pipes-zlib has an outdated bound on ghc-prim, I could lift this bound using,

package pipes-zlib
    allow-newer: ghc-prim

This would have the effect of dropping the upper bound from any constraints on ghc-prim from pipes-zlib.cabal.

[angerman]

Isn't this

allow-newer:
  pipes-zlib:ghc-prim

?

I think this works. We use it a lot. E.g. here https://github.com/input-output-hk/plutus-apps/pull/225/files#diff-b8ed06757045fac949c89f2139a862498ad2b6d1f82c61a31e7c91d6cf0eaa70L28

[jneira]

I think so, we are using it extensively in hls too: https://github.com/haskell/haskell-language-server/blob/e6227440b47e2d05bc5ad1e4d65cba4c037d1d74/cabal-ghc901.project#L47-L66

[bgamari]

Indeed it is. I do think that my proposal is more intuitive but nevertheless it's nice to know that the same thing can be achieved today.

[alt-romes]

I ran into this today. I expected package X\nallow-newer:base to work too, and found this while searching for the "right way". I agree with @bgamari that it would be more intuitive.