make-style variables don’t appear to be expanded in repl_ghci_args

[patrickt]

Describe the bug
In order to pass a file path to the C preprocessor, I define it using a -D style macro in compiler_flags, containing an invocation of $(rootpath ...). This works fine when building the standard target, but the expansion doesn’t seem to take place with repl_ghci_args, even though the docs say that Make-style substitution occurs on repl_ghci_args, and I’m specifying it here.

To Reproduce

1. Check out git@github.com:github/semantic.git and the bazel-experiments branch.
2. Run bazel build //semantic-python:lib and observe everything working.
3. Run bazel run //semantic-python:lib@repl and observe that the preprocessor macro NODE_TYPES_PATH has not expanded its rootpath.

Expected behavior
The given macro should not be ../../../../$(rootpath @tree-sitter-python//:src/node-types.json)
I looked through haskell_impl.bzl in this repo and observed that expand_make_variables exists; is it a matter of calling that? Is it possible for me to do that manually from my build script?

Environment

• OS name + version: macOS Catalina
• Bazel version: 3.1.0
• Version of the rules: 0.12

[aherrmann]

@patrickt Thanks for reporting this and for the detailed issue description. This is indeed a bug in haskell_repl, #1381 should fix it.

I looked through haskell_impl.bzl in this repo and observed that expand_make_variables exists; is it a matter of calling that? Is it possible for me to do that manually from my build script?

That's exactly right, haskell_repl wasn't calling expand_make_variables on ghci_repl_args. This cannot be done externally from the BUILD file but has to be done in the implementation in rules_haskell. #1381 addresses this.

[patrickt]

@aherrmann You are so awesome. Thanks a ton.