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unassigned-return-value

Summary: Non-boolean return value unassigned

Category: Bugs

Avoid

package policy

import rego.v1

allow if {
    # return value not assigned
    lower(input.user.name)
    # ...
}

Prefer

package policy

allow if {
    # return value assigned
    name_lower := lower(input.user.name)
    # ...
}

Rationale​

Calling a built-in function that returns a non-boolean value without actually assigning the returned value is almost always a mistake. Only return of false or undefined will cause evaluation to halt, so a function that e.g. always returns a string will always be evaluated as "truthy". But more importantly — not handling the return value in that case is almost certainly a mistake.

Configuration Options​

This linter rule provides the following configuration options:

rules:
  bugs:
    unassigned-return-value:
      # one of "error", "warning", "ignore"
      level: error

Community​

If you think you've found a problem with this rule or its documentation, would like to suggest improvements, new rules, or just talk about Regal in general, please join us in the #regal channel in the Styra Community Slack!