node not recognized when double brackets on the lhs in JAGS

[audrey-b]

The Bug

When a node is defined on the left hand side using embedded square brackets, such as a[i[1]], it is not recognized as a node and cannot be monitored.

A Reprex

Here, node a cannot be monitored:

sims::sims_simulate("
    a[i[1]] ~ dnorm(0,1)
    b ~ dnorm(0,1)", 
  constants = list(i=c(1,2,3)))

$b
[1] -0.9078546

$i
[1] 1 2 3

an nlists object of an nlist object with 2 numeric elements

Here, node a is monitored, which is the desired behavior:

sims::sims_simulate("
    a[1] ~ dnorm(0,1)
    b ~ dnorm(0,1)")

$a
[1] -0.644611

$b
[1] 0.09873857

an nlists object of an nlist object with 2 numeric elements```

[joethorley]

@audrey-b - Interesting I didn't know this was a possibility! I'm pretty snowed under are you able to fix in a pull request?

[audrey-b]

I spent a couple hours trying to figure it out yesterday but did not succeed, so I will leave it at it for now. I'm not well versed in regex. It seems like the issue is within the internal function stochastic_nodes_pattern, which currently uses

index <- "\\[[^\\]]*\\]"

to extract nodes that have 0 or 1 of: a bracket [ followed by anything but a bracket ], and then followed with a closing bracket ]. This results in discarding nodes that have nested brackets.