Helper to write target factories

[liutiming]

Hi @wlandau, I am wondering if you have a helper to write target factories from existing targets?

I feel it should be doable to have a script that parse the existing targets as a text file and

1. remove the commas
2. change target to target raw
3. add quotation marks, substitute and quote

[wlandau]

I am considering a new tar_deparse() function that would source _targets.R (just like tar_manifest()) and generate a bunch of tar_target_raw() calls using the internal settings of the actual target objects. But I am not committed yet because I do not fully understand the value it would add. I am not sure this adds much convenience for writing target factories, and there may be smoother workarounds when metaprogramming is needed.

[liutiming]

ah sorry. What I meant was that a is already a target name. So you should not need to substitute that with "another_target_name" i.e. "another_target_name" is "a". So substitute seems to be a bit redundant there?

[wlandau]

Yes, if a is the target name and you know it in advance, then you can just write quote(f(a)). substitute(f(a), env = list()) gives the same result, but be careful if you do not set env.

[liutiming]

thanks! how about pattern?

[wlandau]

pattern and command are both expression/language objects, and the metaprogramming is the same.

[liutiming]

Thank you so much! I am getting the hang of it and I realise it is a very monotonous (and error prone) process... Really appreciate the work you have done for STAN and JAGS!