Ending GSoC

As the firm pencils down date for Google Summer of Code is coming up Monday, I figure I'd better make sure everyone understands what I've done and how to use it.

• GhcOptions Record
This record has fields for every GHC option used by cabal. It replaces the ad hoc lists of strings that were used previously. GhcOptions is also a Monoid instance, so one can mapped more specific options onto basic ones. To allow this instance, lots of fields are wrapped in All, Any, First, and Last constructors, which can be kind of a pain when filling the fields manually, but it's a small price to pay for composability.
• Repl Function
This addition to the Cabal API will start an interpreter session. By default, it will load all files from the library component of a package. If the user passes specific files, the function will try to build the component that contains these files, failing if no such component can be found or if multiple components contain the files. If the user wants to load some specific component, this can be specified by the --component flag. Like other functions in the cabal API, there are number of hooks that the user can specify to change default interpretation behavior: preRepl, replHook, and postRepl. The names kind of speak for themselves.
• GHCi Support
The repl function eventually calls an interpret function defined individually for each compiler. Currently, the only compiler with interpretation defined is GHC. GHC's interpret implimentation also defines a series of macros that overload the standard :load and :reload interpreter commands to call cabal repl --enable-reload on the specified component before loading so as to do whatever preprocessing is necessary.
• Other Changes to the Cabal API
Because GHC's interpret function calls the cabal-install tool, I had to add cabal to the list of known programs (including ar, ghc, ghc-pkg, etc). Also, because interpretation does not necessarily require building every single package, the topologically sorted build order list used in building is no longer sufficient. I've added a compBuildMap field to LocalBuildInfo which maps components to their topologically sorted list of dependencies.
• Cabal Repl
The cabal-install tool now has an repl command:

Usage: cabal repl [FILENAME] [FLAGS]
    --enable-reload
Enable file reloading from within an interpreter.
    --disable-reload
Disable file reloading from within an interpreter.
    --component[=COMPONENT]
The component of the cabal package to interpret
Examples:
  cabal repl
Only library component in the package
  cabal repl Examples/Foo.hs
Specific file
  cabal repl Bar.hs --component=myexe
File from specific component
  cabal repl --component=library
Library contained in the package

The usual flags apply as well, of course, and the --enable-reload option isn't really meant for anyone except cabal itself to use when reloading packages.

Oh yeah. Here's the code, and here is the haddock stuff.