RStan is passing the wrong type for the code argument to stanc.js on Windows

[WardBrian]

This has lead to stan-dev/stanc3#1446 and the seven duplicates therein.

I think the issue is the code that reads from a file is returning a vector of strings, rather than just one string. No idea why this is OS-specific.

This might be related to my pr #1124 which touches some of the same code

Description:

This model consistently raises an error on Windows, but not on other platforms:

data {
  int<lower=0> T; # rows
  int<lower=0> N; # cols
  
  matrix[T, N] x;
  matrix[T, N] y;
}

parameters {
  real alpha;
  real beta;
  
  real mu_alpha;
  real<lower=0> sigma_alpha;
  
  real mu_beta;
  real<lower=0> sigma_beta;
}

model {
  
  
  for(i in 1:T){
    for(j in 1:N){
      y[i, j] ~ poisson(exp(alpha + beta*x[i, j]))
    }
  }
  
  alpha ~ normal(mu_alpha, sigma_alpha);
  beta ~ normal(mu_beta, sigma_beta);
  
  mu_alpha ~ normal(0, 1)
  sigma_alpha ~ gamma(2, 2)
  
  mu_beta ~ normal(0, 1)
  sigma_beta ~ gamma(2, 2)
  
}

> rstan::stanc("./m2.stan") yields

Error in rstan::stanc("./m2.stan") : 0
Internal compiler error:
TypeError: b.charCodeAt is not a function

By replacing the stanc.js with the non-minified version, and adding some extra printing code to it, this became clear:

1. b above is the code string
2. In this case, the code is not actually a string, but an array of strings.

That is why this code does not lead to a crash:

code <- paste(readLines('./m2.stan'), collapse="")
rstan::stanc(model_code=code)

(though, it does raise a genuine syntax error, which is good!)

RStan Version:

‘2.36.0.9000’

R Version:

"R version 4.4.2 (2024-10-31 ucrt)"

Operating System:

Windows 11

[WardBrian]

Note that directly using rstan:::stanc_ctx$call("stanc", ...) also never seems to raise this error, so something that is munging model_code is returning something that isn't a string.

The array being passed seems to be split at newlines:
["data {"," int<lower=0> T; # rows"," int<lower=0> N; # cols",""," matrix[T, N] x;"," matrix[T, N] y;","}","parameters {"," real alpha;"," real beta;",""," real mu_alpha;"," real<lower=0> sigma_alpha;",""," real mu_beta;"," real<lower=0> sigma_beta;","}","model {","",""," for(i in 1:T){"," for(j in 1:N){"," y[i, j] ~ poisson(exp(alpha + beta*x[i, j]))"," }"," }",""," alpha ~ normal(mu_alpha, sigma_alpha);"," beta ~ normal(mu_beta, sigma_beta);",""," mu_alpha ~ normal(0, 1)"," sigma_alpha ~ gamma(2, 2)",""," mu_beta ~ normal(0, 1)"," sigma_beta ~ gamma(2, 2)","","}"]

@hsbadr could you look into this? It's generating a lot of noise in the stanc3 repo, and it looks like most of the users are using experimental

[WardBrian]

Cross linking all the places this has surfaced:

• https://discourse.mc-stan.org/t/help-in-finding-solutions-for-the-error-0-248-js-of-ocaml-js-error-18-typeerror-not-a-function-error-in-model-cppcode-errors-operator-is-invalid-for-atomic-vectors/37195
• https://discourse.mc-stan.org/t/failed-to-parse-fit-stan-model-error-rstan/26018/7
• Internal compiler error: TypeError: not a function stanc3#1434
• Internal compiler error: TypeError: a.charCodeAt is not a function stanc3#1446
• Trouble with StanR compilation stanc3#1455
• ERROR IN STAN CODE stanc3#1458
• Rstan error stanc3#1465
• model issue stanc3#1469
• [BUG] Internal Compiler Error stanc3#1472

[WardBrian]

Note: setting my line endings to CRLF on ubuntu still didn't trigger the same behavior as Windows