Show why configuring dependencies failed

[9999years]

When act-as-setup configure fails, it doesn't indicate which dependencies are missing entirely and which ones don't satisfy the version constraints. The errors from cabal build are more informative, but aren't available in all contexts (nixpkgs Haskell builds, for example, use the act-as-setup interface). This makes it immediately clear what sort of dependency error has occurred.

Before (cabal-install 3.12.1.0):

Configuring test-pkg-0.1.0.0...
Error: [Cabal-8010]
Encountered missing or private dependencies:
    base <=4.18,
    foobar,
    test-pkg:{bar-internal, foo-internal}

After:

Configuring test-pkg-0.1.0.0...
Error: [Cabal-8010]
Encountered missing or private dependencies:
    base <=4.18 (installed: 4.19.1.0),
    foobar (missing),
    test-pkg:{bar-internal,foo-internal} (missing: :bar-internal)

Please let me know if you're interested in this patch and I can write tests and polish up the documentation.

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[geekosaur]

Unfortunately, I'm not qualified to determine whether this is logically correct, only that it looks reasonable (and being a spell checker 😛).

[9999years]

Ah, the tests are failing because they pass the exact ID of the base library (which varies per GHC version under test), and that shows up in the output. Not sure how to work around that with the expect tests.

[jasagredo]

You should probably work out how to identify those and replace them with a common string in OutputNormalizer.hs