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double-negative

Summary: Avoid double negatives

Category: Style

Avoid

package negative

import rego.v1

fine if not not_fine

with_friends if not without_friends

not_fine := input.fine != true

without_friends if count(input.friends) == 0

Prefer

package negative

import rego.v1

fine if input.fine == true

with_friends if count(input.friends) > 0

Rationale​

While rules using double negatives — like not no_funds — occasionally make sense, it is often worth considering whether the rule could be rewritten without the negative. For example, not no_funds could be rewritten as funds or has_funds, or funds_available.

Access control policy often includes rules using some form of double negatives, like allow if not deny. That's considered OK, and the double-negative rule is limited to check for a limited list of words:

  • not cannot_
  • not no_
  • not non_
  • not not_,

Configuration Options​

This linter rule provides the following configuration options:

rules:
  style:
    double-negative:
      # 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!