Adding a helper method to pecan's default template namespace, static. Now in templates, you can wrap form field values with static(name, value), e.g.,

<input type="password" name="password" value="${static('password', '')}" />
<input type="hidden" name="token" value="${static('token', 'RANDOMTOKEN')}" />

...and htmlfill will skip over them when pre-filling.  This is useful if you'd like to always enforce a default value for an HTML field.

pecan/core.py

@@ -63,6 +63,13 @@ def error_for(field):
         return ''
     return request.validation_errors.get(field, '')
 
+    
+def static(name, value):
+    if 'pecan.params' not in request.environ:
+        request.environ['pecan.params'] = dict(request.str_params)    
+    request.environ['pecan.params'][name] = value
+    return value
+
 
 class ValidationException(ForwardRequestException):
     def __init__(self, location=None, errors={}):
@@ -75,7 +82,8 @@ class ValidationException(ForwardRequestException):
             if callable(location):
                 location = location()
         merge_dicts(request.validation_errors, errors)
-        request.environ['pecan.params'] = dict(request.str_params)
+        if 'pecan.params' not in request.environ:
+            request.environ['pecan.params'] = dict(request.str_params)
         request.environ['pecan.validation_errors'] = request.validation_errors
         if cfg.get('htmlfill') is not None:
             request.environ['pecan.htmlfill'] = cfg['htmlfill']
@@ -292,6 +300,7 @@ class Pecan(object):
                 state.content_type = self.get_content_type('json')
             else:
                 result['error_for'] = error_for
+                result['static'] = static
                 
             if ':' in template:
                 renderer = self.renderers.get(template.split(':')[0], self.template_path)

tests/templates/form_login.html

@@ -0,0 +1,2 @@
+<input type="text" id="username" name="username" />
+<input type="password" id="password" name="password" value="${static('password', '')}" />

tests/templates/form_login_invalid.html

@@ -0,0 +1,2 @@
+<input type="text" id="username" name="username" value="ryan" />
+<input type="password" id="password" name="password" value="" class="error" />

tests/templates/form_login_valid.html

@@ -0,0 +1,2 @@
+<input type="text" id="username" name="username" />
+<input type="password" id="password" name="password" value="" />

tests/test_validation.py

@@ -624,6 +624,70 @@ class TestValidation(object):
         })
         assert r.status_int == 200
         assert r.body == dumps(dict(error_with=['name']))
+                
+    def test_htmlfill_static(self):
+
+        if 'mako' not in builtin_renderers:
+            return
+
+        class LoginSchema(Schema):
+            username = validators.String(not_empty=True)
+            password = validators.String(not_empty=True)            
+
+        class RootController(object):
+
+            @expose(template='mako:form_login.html',
+                    schema=LoginSchema())
+            def index(self, **kwargs):
+                if request.validation_errors:
+                    return dict()
+                else:
+                    return dict(data=kwargs)
+
+            @expose(schema=LoginSchema(),
+                    error_handler='/errors_with_handler')
+            def with_handler(self, **kwargs):
+                return '%s:%s' % (kwargs['username'], kwargs['password'])
+
+            @expose('mako:form_login.html')
+            def errors_with_handler(self):
+                return dict()             
+
+        def _get_contents(filename):
+            return open(os.path.join(self.template_path, filename), 'r').read()
+
+        # test without error handler
+        app = TestApp(make_app(RootController(), template_path=self.template_path))
+        r = app.post('/', {
+            'username' : 'ryan',
+            'password' : 'password'
+        })
+        assert r.status_int == 200
+        assert r.body == _get_contents('form_login_valid.html')
+
+        # test failure without error handler
+        r = app.post('/', {
+            'username' : 'ryan',
+            'password' : ''
+        })
+        assert r.status_int == 200
+        assert r.body == _get_contents('form_login_invalid.html')
+
+        # test with error handler
+        r = app.post('/with_handler', {
+            'username' : 'ryan',
+            'password' : 'password'
+        })
+        assert r.status_int == 200
+        assert r.body == 'ryan:password'
+
+        # test failure with error handler
+        r = app.post('/with_handler', {
+            'username' : 'ryan',
+            'password' : ''
+        })
+        assert r.status_int == 200
+        assert r.body == _get_contents('form_login_invalid.html')
     
     def test_error_for(self):