#21228 Macros with leading underscores cannot be used in BUILD files in 2.23 Issue created by huonw Describe the bug If someone defines a macro like: def _example(): target(name="_example") This was available for use in

BUILD

files in 2.23.0.dev0 and earlier (including all stable releases), but stopped being available in 2.23.0.dev1 with a hard error. We should either: 1. allow macros with leading underscores 2. do a deprecation cycle to help users update Reproducer: cd $(mktemp -d) cat > pants.toml <<EOF [GLOBAL] pants_version = "2.23.0.dev1" backend_packages = [] build_file_prelude_globs = ["macros.py"] EOF echo 'def _example(): target(name="_example")' > macros.py echo "_example()" > BUILD # OKAY: prints

//:_example

PANTS_VERSION=2.23.0.dev0 pants list :: # BUG: error emitted: "MappingError: Failed to parse ./BUILD ... Name '_example' is not defined" pants list :: Full from the second `pants list ::`:

11:18:22.56 [ERROR] 1 Exception encountered:

Engine traceback:
  in `list` goal
  in Find targets from input specs

MappingError: Failed to parse ./BUILD:
ParseError: BUILD:1: Name '_example' is not defined.

If you expect to see more symbols activated in the below list, refer to <https://www.pantsbuild.org/2.23/docs/using-pants/key-concepts/backends> for all available backends to activate.

All registered symbols: ['PANTS_VERSION', '__defaults__', '__dependencies_rules__', '__dependents_rules__', '_lockfile', '_lockfiles', 'archive', 'build_file_dir', 'docker_environment', 'env', 'experimental_workspace_environment', 'experimental_wrap_as_resources', 'file', 'files', 'http_source', 'local_environment', 'parametrize', 'per_platform', 'relocated_files', 'remote_environment', 'resource', 'resources', 'target']

NB. this occurs in practice in my work repo: we have a macro wrapping

__dependencies_rules__

that's named to mimic it, and thus starts with

__dependencies_rules_...

. Pants version 2.23.0.dev1 OS macOS Additional info Comparison: release_2.23.0.dev0...release_2.23.0.dev1 Potential cause (not confirmed!): #21028, beed36c pantsbuild/pants