A tool to help with fetching Cabal packages from Hackage and importing them as packages into cabal2bazel.

Usage: cabal2bazel --fetch

Examples: cabal2bazel --fetch binary cabal2bazel --fetch binary-0.5.0.2 cabal2bazel --recursive --fetch lens

The process for installing third-party Haskell packages is specified at: https://opensource.google.com/docs/thirdparty/haskell/ cabal2bazel does not (yet) capture all the subtleties of this process, and is no substitute for code review. But it will automate the bulk of chores, including:

• fetching the Cabal package;
• unpacking it into an appropriate directory;
• ensuring the license file is in the expected location;
• generating a BUILD file with suitable rules.
• if --recursive is specified, traversing graph of all dependencies of selected package and importing all of them.

cabal2bazel attempts to map the dependencies of a Cabal library or executable to the 'deps' attribute of the resulting Bazel target.

Things that still need manual attention include:

• optimization modes need to be removed from ghcopts, because Bazel chooses them itself;
• cabal2bazel adds '-Wwarn' to all rules' ghcopts; this might not be desired;
• correct choice of license attributes should be checked;
• generated dependencies might need to be adjusted to point to specific versions of the packages depended upon.

NOTE: You will need an appropriate version of 'cabal' to be available on your path; cabal2bazel uses it for downloading and unpacking packages.

NOTE: Sometimes it is necessary to edit the cabal file and re-run cabal2bazel. In such cases rerun cabal2bazel as follows to resume installation:

cabal2bazel --wire-up

Example: cabal2bazel --wire-up //third_party/haskell/binary/v0_5_0_2