Decide how to address targets that cannot be remade

[tiernanmartin]

Sometimes an external change will occur and a target will no longer be able to be created.

An example of this is cpi which relies on the BLS API. If a change is made to the API -- and it hasn't been addressed by the blsAPI package -- this may result a command that no longer works.

This type of dependency is one of the primary motivators for the project's architecture that separates the original code used to create input data (data_source_plan) from the code used to import a stored version of the input data (data_cache_plan).

While this system works well, I have run into an issue: resetting the drake project (drake::clean()) results in an "outdated" data_source_plan that needs to run again. The external changes made to the BLS API prevent my original code from working, so the project now fails at the prepare_cpi(path= file_out("extdata/source/cpi-2000-2018.csv")) command.

My solution is to remove the targets associated with this input data from both prep_plan and upload_plan and store them in a new plan called target_archive_plan. This new plan is not executed when get_data_source_plan() is run, but it allows me to keep the original source code for this target. If the dependency issue is fixed then targets stored in target_archive_plan may be restored to the other plans; if not then they will remain there as a record of what used to work.

Here is what the data_source_plan now looks like:

get_data_source_plan <- function(){

  prep_plan <- drake::drake_plan(
   ...
  )

  upload_plan <- drake::drake_plan(
    ...
  )

  target_archive_plan <- drake::drake_plan(
    # stored targets go here
  )

 # note that `target_archive_plan` is *not* included below

  data_source_plan <- drake::bind_plans(prep_plan, upload_plan) 

  return(data_source_plan)

}