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New condition syntax

With limitador-server version 1.0.0 (and the limitador crate version 0.3.0), the syntax for conditions within limit definitions has changed.

Changes

The new syntax

The new syntax formalizes what part of an expression is the identifier and which is the value to test against. Identifiers are simple string value, while string literals are to be demarcated by single quotes (') or double quotes (") so that foo == " bar" now makes it explicit that the value is to be prefixed with a space character.

A few remarks:

  • Only string values are supported, as that's what they really are
  • There is no escape character sequence supported in string literals
  • A new operator has been added, !=

The issue with the deprecated syntax

The previous syntax wouldn't differentiate between values and the identifier, so that foo == bar was valid. In this case foo was the identifier of the variable, while bar was the value to evaluate it against. Whitespaces before and after the operator == would be equally important. SO that foo == bar would test for a foo variable being equal to bar where the trailing whitespace after the identifier, and the one prefixing the value, would have been evaluated.

Server binary users

The server still allows for the deprecated syntax, but warns about its usage. You can easily migrate your limits file, using the following command:

limitador-server --validate old_limits.yaml > updated_limits.yaml

Which should output Deprecated syntax for conditions corrected! to stderr while stdout would be the limits using the new syntax. It is recommended you manually verify the resulting LIMITS_FILE.

Crate users

A feature lenient_conditions has been added, which lets you use the syntax used in previous version of the crate. The function limitador::limit::check_deprecated_syntax_usages_and_reset() lets you verify if the deprecated syntax has been used as limit::Limits are created with their condition strings using the deprecated syntax.