forms: check max length against characters, not bytes (#22175)

tests/test_form_pages.py

@@ -1,3 +1,5 @@
+# -*- coding: utf-8 -*-
+
 import json
 import pytest
 import hashlib
@@ -3160,6 +3162,18 @@ def test_form_text_field_submit(pub):
     data = formdef.data_class().get(data_id)
     assert data.data['0'] is None
 
+    # check max length
+    formdef.fields = [fields.TextField(id='0', label='string', type='text', maxlength=10)]
+    formdef.store()
+    resp = get_app(pub).get('/test/')
+    resp.forms[0]['f0'] = 'x' * 11
+    resp = resp.forms[0].submit('submit')
+    assert 'too many characters (limit is 10)' in resp.body
+    # check it counts characters, not bytes
+    resp.forms[0]['f0'] = u'☭' * 10
+    resp = resp.forms[0].submit('submit')
+    assert 'Check values then click submit.' in resp.body
+
 def test_form_items_datasource(pub):
     formdef = create_formdef()
     formdef.fields = [fields.ItemsField(id='1', label='items',

wcs/qommon/form.py

@@ -490,8 +490,10 @@ class TextWidget(quixote.form.TextWidget):
                 maxlength = int(self.attrs.get('maxlength', 0))
             except (TypeError, ValueError):
                 maxlength = 0
-            if maxlength and len(self.value) > maxlength:
-                self.error = _('too many characters (limit is %d)') % maxlength
+            if maxlength:
+                uvalue = self.value.decode(get_publisher().site_charset)
+                if len(uvalue) > maxlength:
+                    self.error = _('too many characters (limit is %d)') % maxlength
             if self.validation_function:
                 try:
                     self.validation_function(self.value)