greta in "imports" of a targets workflow

[smwindecker]

Re: seamless integration of greta into targets

To make greta models available to downstream targets we need to "awaken" the model using a tar_hook_before() per the examples and discussion here and here.

Although these short-term fixes have worked fine, they fail to work if greta is added to the imports argument of tar_option_set() per below example. There is no issue with having greta listed in the packages argument.

tar_option_set(

  # packages that your targets need to run
  packages = c('greta'),
  imports = c('greta')
)

@njtierney has suggested this may have to do with making the entire namespace of greta available in the global environment.

It would be helpful to solve this issue because having the package in the imports argument means your targets pipeline is checking changes in the internal code of package and rerunning the workflow accordingly, per these guidelines about package invalidation.

[njtierney]

This is something that is good to know about, as it could definitely trip people up!

However, I think I would not recommend putting greta in the "imports" argument of tar_option_set as a general rule, although I can imagine there might be exceptions.

I think the preferable answer is to use renv to manage a specific package version of greta, if that is what you require, as recommended in the guidelines about package-based invalidation:

Usually, local package libraries do not need to change very often, and it is best to maintain a reproducible project library using renv.

Rather than loading greta locally on your machine and installing from there. The situation I am imagining where greta is required to be in imports is when you are developing specific functions within greta and are working on it locally and also using a targets pipeline. I'm not sure if that will come up very often?

I'd be curious if this issue arises if putting greta.gp inside of imports as well.

[njtierney]

Also a note that perhaps functions that import, e.g., greta::normal, inside a local package that is imported in targets import, might be causing an issue here as well.