made sure custom strings like MessageID are not converted

tests/testustr.py

@@ -0,0 +1,84 @@
+##############################################################################
+#
+# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""ustr unit tests.
+
+$Id$
+"""
+
+import unittest
+
+from DocumentTemplate.ustr import ustr
+
+
+class force_str:
+    # A class whose string representation is not always a plain string:
+    def __init__(self,s):
+        self.s = s
+    def __str__(self):
+        return self.s
+
+
+class Foo(str):
+
+    pass
+
+
+class Bar(unicode):
+
+    pass
+
+
+class UnicodeTests(unittest.TestCase):
+
+    def testPlain(self):
+        a = ustr('hello')
+        assert a=='hello', `a`
+        a = ustr(force_str('hello'))
+        assert a=='hello', `a`
+        a = ustr(chr(200))
+        assert a==chr(200), `a`
+        a = ustr(force_str(chr(200)))
+        assert a==chr(200), `a`
+        a = ustr(22)
+        assert a=='22', `a`
+        a = ustr([1,2,3])
+        assert a=='[1, 2, 3]', `a`
+
+    def testUnicode(self):
+        a = ustr(u'hello')
+        assert a=='hello', `a`
+        a = ustr(force_str(u'hello'))
+        assert a=='hello', `a`
+        a = ustr(unichr(200))
+        assert a==unichr(200), `a`
+        a = ustr(force_str(unichr(200)))
+        assert a==unichr(200), `a`
+
+    def testExceptions(self):
+        a = ustr(ValueError(unichr(200)))
+        assert a==unichr(200), `a`
+
+    def testCustomStrings(self):
+        a = ustr(Foo('foo'))
+        self.failUnlessEqual(type(a), Foo)
+        a = ustr(Bar('bar'))
+        self.failUnlessEqual(type(a), Bar)
+
+
+def test_suite():
+    suite = unittest.TestSuite()
+    suite.addTest( unittest.makeSuite( UnicodeTests ) )
+    return suite
+
+if __name__ == '__main__':
+    unittest.main(defaultTest='test_suite')

ustr.py

@@ -0,0 +1,62 @@
+##############################################################################
+#
+# Copyright (c) 2001 Zope Corporation and Contributors. All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.0 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+##############################################################################
+"""ustr function.
+
+$Id$
+"""
+
+nasty_exception_str = Exception.__str__.im_func
+
+def ustr(v):
+    """Convert any object to a plain string or unicode string,
+    minimising the chance of raising a UnicodeError. This
+    even works with uncooperative objects like Exceptions
+    """
+    if isinstance(v, basestring):
+        return v
+    else:
+        fn = getattr(v,'__str__',None)
+        if fn is not None:
+            # An object that wants to present its own string representation,
+            # but we dont know what type of string. We cant use any built-in
+            # function like str() or unicode() to retrieve it because
+            # they all constrain the type which potentially raises an exception.
+            # To avoid exceptions we have to call __str__ direct.
+            if getattr(fn,'im_func',None)==nasty_exception_str:
+                # Exception objects have been optimised into C, and their
+                # __str__ function fails when given a unicode object.
+                # Unfortunately this scenario is all too common when
+                # migrating to unicode, because of code which does:
+                # raise ValueError(something_I_wasnt_expecting_to_be_unicode)
+                return _exception_str(v)
+            else:
+                # Trust the object to do this right
+                v = fn()
+                if isinstance(v, basestring):
+                    return v
+                else:
+                    raise ValueError('__str__ returned wrong type')
+        # Drop through for non-instance types, and instances that
+        # do not define a special __str__
+        return str(v)
+
+
+def _exception_str(exc):
+    if hasattr(exc, 'args'):
+        if not exc.args:
+            return ''
+        elif len(exc.args) == 1:
+            return ustr(exc.args[0])
+        else:
+            return str(exc.args)
+    return str(exc)