Add new utility isValidTALESExpression which return if source text of TALES Expression

is compilable or not.
It will be useful For StringField's ExternalValidator who are trying to
validate TALES Expression as input.



git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@43239 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/Utils.py

@@ -3367,3 +3367,22 @@ def reencodeUrlEscapes(url):
       url += [_reencodeUrlEscapes_map[c] for c in part]
   except StopIteration:
     return ''.join(url)
+
+from zope.tales.engine import Engine
+from zope.tales.tales import CompilerError
+
+def isValidTALESExpression(value):
+  """return if given value is valid TALES Expression.
+  This validator only validates Syntax of TALES Expression,
+  it does not tell that Expression is callable on given context
+
+  - value: string we try to compile
+
+  return tuple: (boolean result, error_message or None)
+  """
+  try:
+    Engine.compile(value)
+  except CompilerError, message:
+    return False, message
+  else:
+    return True, None

product/ERP5Type/__init__.py

@@ -165,7 +165,8 @@ ModuleSecurityInfo('Products.ERP5Type.Utils').declarePublic(
     'sortValueList', 'convertToUpperCase', 'UpperCase',
     'convertToMixedCase', 'cartesianProduct', 'sleep', 'getCommonTimeZoneList',
     'int2letter', 'getMessageIdWithContext', 'getTranslationStringWithContext',
-    'Email_parseAddressHeader', 'guessEncodingFromText')
+    'Email_parseAddressHeader', 'guessEncodingFromText',
+    'isValidTALESExpression')
 
 allow_module('Products.ERP5Type.Message')
 ModuleSecurityInfo('Products.ERP5Type.Message').declarePublic('translateString')