Model operations fail to handle external process death gracefully

[myshkin]

Summary:

Under certain circumstances, we encounter a crash at initialization of brm().

Description:

In R/model.R, the compile and check_syntax functions use processx::run() to launch external processes, and then check the status component of the return value against 0 to detect certain failures. Unfortunately, this component gets set to NA if the external process is killed, per [https://processx.r-lib.org/reference/run.html](the processx docs), and so the check can generate the error below.

Reproducible Steps:

Unfortunately, we have not yet figured out what is causing the external processes to die, and are seeing this in only about 10 percent of runs.

Current Output:

When the crash occurs, we see

Error in if (run_log$status != 0) { :
  missing value where TRUE/FALSE needed
Calls: brm ... eval -> .fun -> <Anonymous> -> initialize -> <Anonymous>

Expected Output:

I assume the module should check for NA and report accordingly.

Current Version:

Observed in v2.26.1, but the if statement in question remains in the v2.27.0 code.

[rok-cesnovar]

Thanks @myshkin for reporting. I moved this to the cmdstanr repository, where I believe the issue is. Will first try to reproduce and then fix the issue ASAP.