ruby-grape/grape · error · ArgumentError

#{name} must be an integer greater than or equal to zero

Error message

#{name} must be an integer greater than or equal to zero

What it means

Each `min:`/`max:` bound passed to the `length` validator must be a non-negative Integer (`validate_boundary!`). Negative numbers and non-integers (strings, floats) are rejected with ArgumentError at definition time — these are declaration bugs, not per-request validation failures.

Source

Thrown at lib/grape/validations/validators/length_validator.rb:45

          return unless (!@min.nil? && param.length < @min) || (!@max.nil? && param.length > @max) || (!@is.nil? && param.length != @is)

          validation_error!(attr_name, message do
            if @min && @max
              translate(:length, min: @min, max: @max)
            elsif @min
              translate(:length_min, min: @min)
            elsif @max
              translate(:length_max, max: @max)
            else
              translate(:length_is, is: @is)
            end
          end)
        end

        private

        def validate_boundary!(name, val)
          raise ArgumentError, "#{name} must be an integer greater than or equal to zero" if !val.nil? && (!val.is_a?(Integer) || val.negative?)
        end
      end
    end
  end
end

View on GitHub (pinned to 22d7975629)

Solutions

1. Pass non-negative Integers: `length: { min: 2, max: 10 }`
2. Convert config-sourced values before the DSL sees them: `min: cfg[:min].to_i` and clamp negatives
3. Omit the key entirely rather than passing 0 when no lower bound is wanted

Example fix

# before
requires :bio, type: String, length: { min: '10', max: 500 }

# after
requires :bio, type: String, length: { min: 10, max: 500 }

def valid_bound?(value)
  value.nil? || (value.is_a?(Integer) && !value.negative?)
end

def valid_length_boundaries?(length_opts)
  valid_bound?(length_opts[:min]) && valid_bound?(length_opts[:max])
end

begin
  requires :bio, type: String, length: { min: cfg[:min], max: cfg[:max] }
rescue ArgumentError => e
  raise "length bounds must be non-negative Integers: #{e.message}"
end

When it happens

Trigger: `length: { min: -1 }`; `length: { max: '10' }` (string from env/config); `length: { min: 3.5 }` (float).

Common situations: ENV-sourced bounds passed as strings without conversion; floats copied in from calculators or other validator configs.

Related errors

• is must be an integer greater than zero
• min #{@min} cannot be greater than max #{@max}
• is cannot be combined with min or max
• must supply type for coerce_with
• coerce_with disallowed for type: JSON

AI-assisted analysis of ruby-grape/grape@22d7975629 (2026-08-21). Data as JSON: /api/errors/0df78deb5fe0d042. Report an issue: GitHub.