Provide a way to substitute values from volatile-status.txt #1008
Description
Use case
- I have a build that creates binary with a versioned name. E.g.
server.YYYYMMDD - I want the .deb file to include that time stamp in the name
- Within the deb package, I have an /etc/init script that has a symlink to server.yymmdd.
- How can I get pkg_mklink() to do that? Likewise for pkg_mkdirs.
Obvious constraint:
- You can't read bazel-out/volatile-status.txt at analysis time, when much of mappings takes place
Idea 1
Have all the writers be able to read volatile-status and late substitute
Yeech. That fan out is infinite.
Idea 2
Add a manifest rewriter step that can do that. If any of the providers have a need substitute bit, invoke it
Idea 3
Do it at analysis time by
- having the tool that creates workspace status also write a .bzl file with a well known name.
- custom pkg_* rules that load the .bzl file and do the substitution.
Could we generalize that so people don't need their own rules?
Maybe:
- add PackageVariablesInfo as an input to more rules.
- user creates custom rule to load that .bzl file and return the provider.