ghc-pkg should not accept unversioned depends

[duncan]

Historically ghc-pkg accepted a format where the "depends:" field did not require version numbers. Then ghc would just resolve it to some installed version. However now that ghc bakes in the version number to libraries when it compiles them it really crucial that a package gets linked with exactly the versions of packages it was built against. Allowing ghc-pkg to accept unversioned depends and resolving them to some random installed version is just asking for trouble.

It's not too serious since Cabal always uses versioned depends, however I just noticed that older autoconf/automake build systems do not.

So, in summary allowing undersioned depends is just asking for trouble and ghc-pkg should reject them.

[simonmar]

In the past this was to make our lives easier in the GHC build system, but now that we use Cabal for building libraries it isn't necessary. Let's remove it in 6.10, and give a deprecated warning in 6.8.2.

[simonmar]

To merge into 6.8:

Wed Nov 14 15:30:10 GMT 2007  Simon Marlow <simonmar@microsoft.com>
  * FIX #1837: emit deprecated message for unversioned dependencies

I've also removed unversioned dependencies completely in the HEAD.

[igloo]

Merged

[duncan]

It seems there is a regression here. See #2705. Apparently unversionend dependencies are silently allowed.

It might be that's because "foo" gets parsed as a package id as PackageId "foo" (Version [] []), ie an empty version.

[igloo]

Looks like when the warning was removed, the test was too. I've reinstated it.