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use-in-operator

Summary: Use in to check for membership

Category: Idiomatic

Avoid

package policy

import rego.v1

# "Old" way of checking for membership - iteration + comparison
allow if {
    "admin" == input.user.roles[_]
}

Prefer

package policy

import rego.v1

allow if {
    "admin" in input.user.roles
}

Rationale​

Using in for membership checks clearly communicates intent, and is less prone to errors. This is especially true when checking if something is not part of a collection.

Configuration Options​

This linter rule provides the following configuration options:

rules:
  idiomatic:
    use-in-operator:
      # 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!