Example out of date?

Looks like the opam_package rule added a new argument, 'type', which is missing. It also seems like the available types won't support the format that cmdliner uses: tbz.

11:14 $ cd examples && bazel build ...
Starting local Bazel server and connecting to it...
...........
ERROR: /Users/josephprice/dev/github.com/ostera/rules_reason/examples/3rdparty/opam/deps.bzl:8:5: //external:opam.cmdliner: missing value for mandatory attribute 'type' in 'opam_package' rule
ERROR: /Users/josephprice/dev/github.com/ostera/rules_reason/examples/3rdparty/opam/deps.bzl:8:5: //external:opam.cmdliner: invalid value in 'type' attribute: has to be one of 'zip', 'jar', 'war', 'tar.gz', 'tgz', 'tar.bz2' or 'tar.xz' instead of ''
ERROR: error loading package 'external': Package 'external' contains errors
INFO: Elapsed time: 0.622s
INFO: 0 processes.
FAILED: Build did NOT complete successfully (0 packages loaded)

Start with examples/3rdparty/opam/deps.bzl, especially the opam.cmdliner declaration at the reported line, and compare it with the opam_package rule's required attributes. Check how the example represents the tbz archive type, then rerun cd examples && bazel build ...; done means the example loads and builds without the reported attribute or archive-type errors.