RUBY-2863 Split excessive precision exception from out of range exception in Decimal128

lib/bson/decimal128.rb

@@ -305,16 +305,15 @@ def message
       end
     end
 
-    # Raised when the exponent or significand provided is outside the valid range.
-    #
-    # @api private
+    # Raised when the exponent is outside the valid range.
     #
     # @since 4.2.0
     class InvalidRange < RuntimeError
 
       # The custom error message for this error.
       #
       # @since 4.2.0
+      # @deprecated
       MESSAGE = 'Value out of range for Decimal128 representation.'
 
       # Get the custom error message for the exception.
@@ -330,6 +329,21 @@ def message
       end
     end
 
+    # Raised when the significand provided is outside the valid range.
+    #
+    # @note This class derives from InvalidRange for backwards compatibility,
+    #   however when RUBY-1806 is implemented it should be changed to derive
+    #   from the base BSON exception class.
+    class UnrepresentablePrecision < InvalidRange
+
+      # Get the custom error message for the exception.
+      #
+      # @return [ String ] The error message.
+      def message
+        'The value contains too much precision for Decimal128 representation'
+      end
+    end
+
     Registry.register(BSON_TYPE, self)
   end
 end

lib/bson/decimal128/builder.rb

@@ -85,9 +85,13 @@ def parts_to_bits(significand, exponent, is_negative)
       private
 
       def validate_range!(exponent, significand)
-        unless valid_significand?(significand) && valid_exponent?(exponent)
+        unless valid_exponent?(exponent)
           raise Decimal128::InvalidRange.new
         end
+
+        unless valid_significand?(significand)
+          raise Decimal128::UnrepresentablePrecision.new
+        end
       end
 
       def valid_significand?(significand)

spec/bson/decimal128_spec.rb

@@ -309,6 +309,22 @@
         it_behaves_like 'an initialized BSON::Decimal128'
       end
     end
+
+    context 'when range is exceeded' do
+      it 'raises InvalidRange' do
+        lambda do
+          described_class.new('1e10000')
+        end.should raise_error(BSON::Decimal128::InvalidRange, /Value out of range/)
+      end
+    end
+
+    context 'when precision is exceeded' do
+      it 'raises UnrepresentablePrecision' do
+        lambda do
+          described_class.new('1.000000000000000000000000000000000000000000000000001')
+        end.should raise_error(BSON::Decimal128::UnrepresentablePrecision, /The value contains too much precision/)
+      end
+    end
   end
 
   context 'when deserializing' do

spec/spec_tests/common_driver_spec.rb

@@ -68,7 +68,8 @@
           let(:valid_errors) do
             [
               BSON::Decimal128::InvalidString,
-              BSON::Decimal128::InvalidRange
+              BSON::Decimal128::InvalidRange,
+              BSON::Decimal128::UnrepresentablePrecision,
             ]
           end