Stack overflow when running partial eval on a rule where variable is accidentally repeated

[TheLunaticScripter]

This is the policy that I'm evaluating. I accidentally duplicated a variable and then ran a partial evaluation on the rule. As a result, I got a stack overflow error. Here is my policy

package rule

sql {
  allowed[_]
}
allowed[file] {
  some file
  file = data.file[file]
  file.owner = input.user.name
}

with the following input

{
  "user": {
    "name": "alice"
  }
}

When I run this command

opa eval -p -i input.json -b . data.rules.sql=true --unknowns data.file -f pretty

I get the stack overflow

To fix this I modified either the some file variable or the file = data.file to be something else for example files and it works as expected.

I believe that this is expected behavior in that the file variable should not be declared in more than one place but I would have expected an unsafe rego error.

[srenatus]

Looking into this 👀

[srenatus]

Note that this may also happen not by accident. A boiled-down version of this would be

package test

p {
  q[_]
}
q[x] {
  x = input[x]
}

where, with input and object, q would be the set of all key/value pairs that match, i.e. input = {"x": "x"} would yield q = { "x" }.

The infinite recursion happens in copy propagation, when running PE in shallow mode, it won't occur.