Add optional type validation

5 files changed, 69 insertions, 3 deletions

diff --git a/lib/slop/error.rb b/lib/slop/error.rb
index ddfa1a7..b83cab3 100644
--- a/lib/slop/error.rb
+++ b/lib/slop/error.rb
@@ -38,4 +38,16 @@ module Slop
   # Suppress with the `suppress_errors` config option.
   class MissingRequiredOption < Error
   end
+
+  # Raised when a given option is provided by the user and does not
+  # match the expected format for that type. This is only raised if
+  # validate_types is set to true.
+  class InvalidOptionValue < Error
+    attr_reader :flag
+
+    def initialize(msg, flag)
+      super(msg)
+      @flag = flag
+    end
+  end
 end
diff --git a/lib/slop/option.rb b/lib/slop/option.rb
index 093b37f..3afc93a 100644
--- a/lib/slop/option.rb
+++ b/lib/slop/option.rb
@@ -56,7 +56,11 @@ module Slop
           raise Slop::MissingArgument.new("missing argument for #{flag}", flags)
         end
       else
-        @value = call(value)
+        if validate_type? && !valid?(value) && !suppress_errors?
+          raise Slop::InvalidOptionValue.new("invalid value for #{flag}", flags)
+        end
+
+        @value = valid?(value) && call(value)
       end
 
       block.call(@value) if block.respond_to?(:call)
@@ -107,6 +111,13 @@ module Slop
       config[:required]
     end
 
+    # Returns true if an exception should be raised when this option value can't
+    # be parsed into the desired type or does not conform to the expected type's
+    # format
+    def validate_type?
+      config[:validate_types]
+    end
+
     # Returns all flags joined by a comma. Used by the help string.
     def flag
       flags.join(", ")
@@ -119,6 +130,13 @@ module Slop
       key.to_sym
     end
 
+    # Override this if you want to provide a custom validator for a type. This
+    # method must return whether the provided value is valid for the current
+    # argument's type
+    def valid?(value)
+      true
+    end
+
     # Returns true if this option should be displayed with dashes transformed into underscores.
     def underscore_flags?
       config[:underscore_flags]
diff --git a/lib/slop/options.rb b/lib/slop/options.rb
index 17e9501..5e71eac 100755
--- a/lib/slop/options.rb
+++ b/lib/slop/options.rb
@@ -7,6 +7,7 @@ module Slop
       type:             "null",
       banner:           true,
       underscore_flags: true,
+      validate_types:   false,
     }
 
     # The Array of Option instances we've created.
@@ -24,6 +25,9 @@ module Slop
     # The String banner prefixed to the help string.
     attr_accessor :banner
 
+    # Whether we should validate types of values provided by the user
+    attr_accessor :validate_types
+
     def initialize(**config, &block)
       @options    = []
       @separators = []
diff --git a/lib/slop/types.rb b/lib/slop/types.rb
index 83e4a0b..a08537d 100644
--- a/lib/slop/types.rb
+++ b/lib/slop/types.rb
@@ -22,6 +22,13 @@ module Slop
     attr_accessor :explicit_value
 
     FALSE_VALUES = [false, 'false', 'no', 'off', '0'].freeze
+    TRUE_VALUES = [true, 'true', 'yes', 'on', '1'].freeze
+    VALID_VALUES = (FALSE_VALUES + TRUE_VALUES).freeze
+
+    def valid?(value)
+      return true if value.is_a?(String) && value.start_with?("--")
+      value.nil? || VALID_VALUES.include?(value)
+    end
 
     def call(value)
       self.explicit_value = value
@@ -52,8 +59,14 @@ module Slop
 
   # Cast the option argument to an Integer.
   class IntegerOption < Option
+    INT_STRING_REGEXP = /\A[+-]?\d+\z/.freeze
+
+    def valid?(value)
+      value =~ INT_STRING_REGEXP
+    end
+
     def call(value)
-      value =~ /\A[+-]?\d+\z/ && value.to_i
+      value.to_i
     end
   end
   IntOption = IntegerOption
@@ -62,8 +75,12 @@ module Slop
   class FloatOption < Option
     FLOAT_STRING_REGEXP = /\A[+-]?(?:0|[1-9]\d*)(?:\.\d*)?(?:[eE][+-]?\d+)?\z/.freeze
 
+    def valid?(value)
+      value =~ FLOAT_STRING_REGEXP
+    end
+
     def call(value)
-      value =~ FLOAT_STRING_REGEXP && value.to_f
+      value.to_f
     end
   end
 
diff --git a/test/error_test.rb b/test/error_test.rb
index d9c71ab..341fa75 100644
--- a/test/error_test.rb
+++ b/test/error_test.rb
@@ -63,3 +63,18 @@ describe Slop::MissingRequiredOption do
     opts.parse []
   end
 end
+
+describe Slop::InvalidOptionValue do
+  it "raises when an option has an invalid value" do
+    opts = Slop::Options.new(validate_types: true)
+    opts.integer "-n", "--number", default: 10
+    assert_raises(Slop::InvalidOptionValue) { opts.parse %w(-n foo) }
+  end
+
+  it "does not raise when errors are suppressed" do
+    opts = Slop::Options.new(validate_types: true, suppress_errors: true)
+    opts.integer "-n", "--number", default: 10
+    r = opts.parse %w(-n foo)
+    assert_equal(10, r[:n])
+  end
+end