Add min and max validation in TTY::Prompt::MultiList

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Change log
 
+## [Unreleased]
+* Add validation to ensure min is less than or equal to max in #multi_select
+
 ## [v0.23.1] - 2021-04-17
 
 ### Changed

lib/tty/prompt/multi_list.rb

@@ -23,20 +23,23 @@ def initialize(prompt, **options)
         @echo = options.fetch(:echo, true)
         @min  = options[:min]
         @max  = options[:max]
+        validate_min_max
       end
 
       # Set a minimum number of choices
       #
       # @api public
       def min(value)
         @min = value
+        validate_min_max
       end
 
       # Set a maximum number of choices
       #
       # @api public
       def max(value)
         @max = value
+        validate_min_max
       end
 
       # Callback fired when enter/return key is pressed
@@ -45,7 +48,7 @@ def max(value)
       def keyenter(*)
         valid = true
         valid = @min <= @selected.size if @min
-        valid = @selected.size <= @max if @max
+        valid &= @selected.size <= @max if @max
 
         super if valid
       end
@@ -219,6 +222,19 @@ def render_menu
 
         output.join
       end
+
+      # Validate min and max requirements are within bounds
+      #
+      # @raise [ConfigurationError]
+      #   raised when min is greater than max
+      #   or when min is less than available choices
+      #
+      # @api private
+      def validate_min_max
+        return unless @min && @max && @min > @max
+
+        raise ConfigurationError, "min cannot be greater than max"
+      end
     end # MultiList
   end # Prompt
 end # TTY

spec/unit/multi_select_spec.rb

@@ -17,8 +17,12 @@ def output_helper(prompt, choices, active, selected, options = {})
     out = []
     out << "\e[?25l" if init
     out << prompt << " "
-    out << "(min. #{options[:min]}) " if options[:min]
-    out << "(max. #{options[:max]}) " if options[:max]
+    if options[:min] || options[:max]
+      minmax_help = []
+      minmax_help << "min. #{options[:min]}" if options[:min]
+      minmax_help << "max. #{options[:max]}" if options[:max]
+      out << "(#{minmax_help.join(', ')}) "
+    end
     out << selected.join(", ")
     out << " " if (init || hint) && !selected.empty?
     out << "\e[90m(#{hint})\e[0m" if hint
@@ -905,4 +909,42 @@ def exit_message(prompt, choices)
       expect(prompt.output.string).to eq(expected_output)
     end
   end
+
+  context "with :min and :max" do
+    it "raises error when min is greater than max" do
+      choices = %w[A B C]
+      prompt.input << " " << "\r"
+      prompt.input.rewind
+
+      expect {
+        prompt.multi_select("What letter?", choices, min: 3, max: 2)
+      }.to raise_error(TTY::Prompt::ConfigurationError,
+                       /min cannot be greater than max/)
+    end
+
+    it "requires number of choices" do
+      choices = %w[A B C D]
+      prompt.on(:keypress) { |e|
+        prompt.trigger(:keyup)   if e.value == "k"
+        prompt.trigger(:keydown) if e.value == "j"
+      }
+
+      prompt.input << " " << "\r" << "j" << " " << "\r"
+      prompt.input.rewind
+
+      value = prompt.multi_select("Select letters?", choices, min: 2, max: 3)
+      expect(value).to eq(%w[A B])
+
+      expected_output =
+        output_helper("Select letters?", choices, "A", [], init: true, min: 2, max: 3,
+          hint: "Press #{up_down} arrow to move, Space to select and Enter to finish") +
+        output_helper("Select letters?", choices, "A", %w[A], min: 2, max: 3) +
+        output_helper("Select letters?", choices, "A", %w[A], min: 2, max: 3) +
+        output_helper("Select letters?", choices, "B", %w[A], min: 2, max: 3) +
+        output_helper("Select letters?", choices, "B", %w[A B], min: 2, max: 3) +
+        exit_message("Select letters?", %w[A B])
+
+      expect(prompt.output.string).to eq(expected_output)
+    end
+  end
 end