ghc-pkg should not report duplicate depends

[duncan]

$ ghc-pkg field regex-base-0.72.0.1 depends
depends: base-3.0.1.0 array-0.1.0.0 base-3.0.1.0 bytestring-0.9.0.1

Note the base-3.0.1.0 base-3.0.1.0. This is clearly silly. It causes problems for Cabal. Although we can easily work around this using nub it'd be better if duplicate depends were never reported or better yet rejected or eliminated at package registration time.

(I'm not sure how it ended up this way, I don't think Cabal makes package registration files with duplicate depends)

[igloo]

I can't reproduce this; in the HEAD:

$ ghc-pkg field regex-base-0.72.0.1 depends
depends: array-0.1 base-3.0 bytestring-0.9

and with 6.8.2:

$ ghc-pkg field regex-base-0.72 depends    
depends: base-3.0.1.0 bytestring-0.9.0.1 array-0.1.0.0

Can you give instructions for reproducing it, please?

[duncan]

My guess is to make a ghc-pkg registration file with a duplicate value in the 'depends' field and then register that package.

Really it'd be better if it were rejected at registration time.

[simonmar]

Fixed:

Mon Aug 18 12:24:34 BST 2008  Simon Marlow <marlowsd@gmail.com>
  * Test for and reject duplicate dependencies (#2330)