Minimal (?) repo that contains Haskell build set up with rules_bazel, with a
nixpkgs-sourced GHC, and is able to build the results using Bazel from within
nix-build itself with the same toolchain.
Latter is contrieved, since nix-build can't be run inside nix-build, so
rules_haskell can't source its dependent toolchain from nix when bazel is
being run inside a nix-build. See WORKSPACE.nix.part file and release.nix
for details.
Running inside nix-build is needed if you want to use Hydra CI, for example, or depend on Bazel-built binaries from other nix files (maybe for a nixops deployment).
The contents of the nix dir implement niv-style nix version pinning, so the
deps are hermetic and independent of the nix-channel version of the user.
The release.nix file is the main nix-build target, resulting in binaries,
tests and test results.
The treetide dir is the monorepo top.
treetide/thirdparty/haskell/BUILD along with ghc.nix define the libraries
we import from Nix.
treetide/haskell/build_defs contains some Bazel shorthands for declaring
common deps.
treetide/haskell/extended contains some extended upstream libs, using
the extended pattern (thus the name extended... ok you likely get it).
Other dirs in the monorepo are laid out according to project structure. Now
we just have the foo_* family of a toy library, test and binary, along with
their BUILD rules.
.bazelignore can be used to exclude eventual node_modules inside the
monorepo, so Bazel doesn't get confused by BUILD files in there.
.bazelrc sets up some Bazel compatibility flags, and instructs
rules_haskell to pull toolchains from Nix. Note: latter instruction is
dropped when building using nix-build, see release.nix.
Having nix installed is a prerequisite.
To build locally while developing:
1) Get a nix shell using nix-shell.
2) Then bazel build -c opt //treetide/....
3) Test using LC_ALL=C.UTF-8 ./bazel-bin/treetide/foo_test.
Note: can also execute single-target REPL, or set up REPL rules for multi-target repl.
Note: can test directly using bazel test -c opt //treetide/..., but that
needs a custom main wrapper that forces GHC into UTF-8 mode. But that's a
different story... Ping if interested.
Execute nix-build release.nix. This will build all targets and run the tests.
The symlinked results output has a directory for the binaries (executables)
and tests, respectively. The results-2 dir contains the test logs (if
successful).
Note: there are some tools available in the nix-shell, see
README.haskell.md for details.
Cleanup PRs, additional tooling welcome!