Behavior of the default rules for object with index

[mingweishih]

When trying the default rules, I notice that default var[index] = value has the following behaviors

• If the index is a scalar value, OPA will initialize the var as an object.
  For example,
  Input

  default z[1] = 1
  

  Output

  "z": { "1": 1 }
  

• If the index is an undefined reference, the OPA will raise error
  Input

  default m[n] = 1
  

  Output

  rego_unsafe_var_error: var n is unsafe
  

• If the index is defined reference or a comprehension, OPA will ignore the index
  Case 1:
  Input

  n = 5
  default m[n] = 1
  

  Output

  "m": 1,
  "n": 5
  

  Case 2:
  Input

  default y[[x | x = 5]] = 1
  

  Output

  "y": 1
  

Are these behaviors by-design?

[srenatus]

Case 1 and 2 look like bugs to me. They should both be invalid and rejected by the compiler.

[anderseknert]

Wow! Multiple issues reported with default assignment on one day. And as far as I know the only reported issues on default assignment 😅

https://github.com/orgs/open-policy-agent/discussions/338
open-policy-agent/opa#5645

[mingweishih]

Case 1 and 2 look like bugs to me. They should both be invalid and rejected by the compiler.

So, is the default rule supposed to only allow variable assignment?