New cmdstan_defaults() method for getting CmdStan's default argument values

[avehtari]

Closes #1133

Finding the CmdStan default arguments for different methods from the documentation is not easy, and many arguments are named differently in CmdStan and in CmdStanR. New model method $cmdstan_defaults() gets the defaults calling CmdStan itself and maps the argument names to those used by CmdStanR,

Copyright and Licensing

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Aki Vehtari

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license the submitted work under the following licenses:

• Code: BSD 3-clause (https://opensource.org/licenses/BSD-3-Clause)
• Documentation: CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

[codecov-commenter]

Codecov Report

❌ Patch coverage is 99.23664% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 91.14%. Comparing base (5809552) to head (b807f16).
⚠️ Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
R/model.R	99.23%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1167      +/-   ##
==========================================
+ Coverage   90.85%   91.14%   +0.29%     
==========================================
  Files          14       15       +1     
  Lines        5924     6065     +141     
==========================================
+ Hits         5382     5528     +146     
+ Misses        542      537       -5     

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[jgabry]

Any idea what's up with the tests failing on some of the runs but not others?

[avehtari]

All windows tests and one macOS test failing, but couldn't yet figure out why. Will investigate tomorrow

[jgabry]

I think we can ignore the Mac failure, that’s unrelated. So yeah, it’s just the Windows tests. I don’t have Windows locally either, but maybe Claude will have some ideas.

[avehtari]

maybe Claude will have some ideas.

Pointing Claude twice to the github Windows test report helped. The model call was missing tbb path, and the solution did already exist in run_info_cli in cpp_opts.R. The Windows tests are now also passing

[jgabry]

Here's a first round of comments. I might have more after I take another look, but these are the first things I noticed.

[jgabry]

I made a few small changes (nothing that affects user-facing behavior) to slightly simplify some of the code and make a few parts easier to read (for a human at least). I think this is ready except for one thing: the name chains (instead of num_chains) is now correct, but the default number of chains in cmdstanr (4) and cmdstan (1) are different. So technically the new method is correct that the cmdstanr default is 1, but that's not very useful for the cmdstanr user. So maybe we should remove chains from the returned argument list since the default is already explicit in the sample method in cmdstanr? What do you think?

[avehtari]

I had removed chains in 92d1b89, and I didn't notice that Claude put it back in baf13bc as part of the parser change which affected some CmdStan default keys. I did read through the diff, but not carefully enough and thought that the changes in the map code where only because of changes on the right hand side. Fixed now

[jgabry]

Ok thanks, looks good to me. Merging now