Unsafe var in object reports location of object, not the var

[anderseknert]

package play

obj := {
    "foo": "bar",
    "baz": qux,
}

In the example above, qux is unsafe and is correctly reported as such:

1 error occurred: policy.rego:3: rego_unsafe_var_error: var qux is unsafe

But qux is not located on line 3 but 5. This doesn't matter much for a trivial case like this, but can be quite annoying when defining large objects in e.g. tests, and having an accidentally unsafe var result in an error without a correct location.

[abhiii71]

Hi @anderseknert , I’m trying to understand this issue but I’m having trouble locating it in my setup. Could you guide me on how to approach or reproduce this problem? Thanks!

[anderseknert]

Reproducing should be easy. Just put the example code from the description in a policy file (say p.rego) and then run:

opa eval -f pretty -d p.rego data.play.obj

And you should see:

1 error occurred: p.rego:3: rego_unsafe_var_error: var qux is unsafe

Running that command with a debugger attached should help identify the whereabouts of the issue... but without having done that — it's the compiler doing this check, so that's where I'd start. The compiler does rewrites of all policies, and the Compiler Explorer (as available via e.g. VS Code and right-clicking inside a policy followed by "Source Actions...") is a good way to visualize that, as the screenshot below shows.

The compiler however keeps a mapping of locations in the original policy and the rewritten one... and if I were to guess, something in that process is not going as expected here.

Your help is much appreciated! Just be aware that the compiler and its code can be rather complex, and non-obvious. So don't feel bad if you get lost/stuck. Just let us know and perhaps we can take a look together.

[stale[bot]]

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