Misc notes

Extensions

WORKSPACE, and BUILD were originally without an extension, but since v0.25, they support .bazel, but not .bzl. MODULE requires a .bazel extension to be recognized by Bzlmod.
- These are meant to be declarative files, although legacy WORKSPACE could also contain code.
- They cannot contain Starlark def or the load instruction
macros and rules contain the Starlark logic, normally with .bzl extension. For legacy compatibility, they can also use .sky extension from when Starlark was called Skylark.

The .gn extension, as in BUILD.gn is used by the Generate Ninja tool, which is similar to Bazel, but not compatible with it.

Within a script, a reference like :foo refers to the target named foo in the current package.

Bazel uses MVS for version selection, just like Go modules.

Bazel defines 3 placeholders usable in some files:

Placeholder	Resolution	Use cases
`%workspace%`	Root of the current workspace	local disk cache, log redirects, project-specific tools
`%user_home%`	$HOME / %USERPROFILE%	User-specific caches or shared credential files
`%usedid%`	Username of the current user	Creating unique subdirs in shared folders e.g., `/tmp/%userid%`

It is a bad idea to reference :

/tmp: won't work on Windows
$HOME, even as ${HOME} : may not be replaced if not run from the CLI by a full shell.
~ : not recognized outside RC files; even there, only works as first character.

Contrary to some Gemini/Claude assertions, these placeholders are not supported in the RC files, though.

Bazel does NOT limit the size of the build cache, or expire items in it.

When deploying a local cache, add a cron task to clean it up, like

find <pathtocache> -type f -atime +30 -delete