Fix options with value="" get selected

Closes issue formencode#3

formencode/htmlfill.py

@@ -521,7 +521,7 @@ def handle_option(self, attrs):
             "<option> outside of <select> at %i:%i" % self.getpos())
         if self.in_select != False:
             if self.force_defaults or self.in_select in self.defaults:
-                if self.selected_multiple(self.defaults.get(self.in_select, ''),
+                if self.selected_multiple(self.defaults.get(self.in_select),
                                           self.get_attr(attrs, 'value', '')):
                     self.set_attr(attrs, 'selected', 'selected')
                     self.add_key(self.in_select)
@@ -537,7 +537,7 @@ def selected_multiple(self, obj, value):
         identity is used.
         """
         if obj is None:
-            return value == ""
+            return False
         if isinstance(obj, (str, unicode)):
             return obj == value
         if hasattr(obj, '__contains__'):

tests/test_htmlfill.py

@@ -388,6 +388,34 @@ def test_force_defaults_select():
     rendered_html = htmlfill.render(html, defaults=dict())
     assert expected_html == rendered_html, rendered_html
 
+def test_select_empty_option_value_selected():
+    html = """
+<select name="select-1" class="my_select">
+  <option value="">this is option-1</option>
+</select>
+"""
+    expected_html = """
+<select name="select-1" class="my_select">
+  <option value="" selected="selected">this is option-1</option>
+</select>
+"""
+    rendered_html = htmlfill.render(html, defaults={"select-1": ""})
+    assert expected_html == rendered_html, rendered_html
+
+def test_select_empty_option_value_not_selected():
+    html = """
+<select name="select-1" class="my_select">
+  <option value="">this is option-1</option>
+</select>
+"""
+    expected_html = """
+<select name="select-1" class="my_select">
+  <option value="">this is option-1</option>
+</select>
+"""
+    rendered_html = htmlfill.render(html, defaults={})
+    assert expected_html == rendered_html, rendered_html
+
 
 def test_script_quoting():
     html = """