Ported the lazy expression into zope.tales and require a new version of it.

doc/CHANGES.rst

@@ -11,6 +11,8 @@ Trunk (unreleased)
 Restructuring
 +++++++++++++
 
+- Ported the lazy expression into zope.tales and require a new version of it.
+
 - Updated Five documentation to clarify its role in regard to Zope packages.
 
 - Removed the deprecated ``five:containerEvents`` directive, which had been

setup.py

@@ -130,7 +130,7 @@ setup(name='Zope2',
       'zope.size',
       'zope.structuredtext',
       'zope.tal',
-      'zope.tales',
+      'zope.tales >= 3.5.0',
       'zope.testbrowser',
       'zope.testing',
       'zope.traversing',

src/Products/PageTemplates/DeferExpr.py

@@ -10,48 +10,7 @@
 # FOR A PARTICULAR PURPOSE
 #
 ##############################################################################
-"""Lazy expression handler
 
-A lazy expressions is implemented similarly to the defer expression
-but has a different result. While a defer expression is evaluated
-every time it is used according to its context a lazy expression is
-evaluted only the first time it is used. Lazy expression are known
-under the name lazy initialization of variables, too.  A common use
-case for a lazy expression is a lazy binding of a costly expression.
-While one could call an expression only when it's required it makes
-sense to define it only one time when it could be used multiple times.
-
-Example
-
-    <div tal:define="lazyvar lazy:here/suckMyCPU">
-        <div tal:condition="foo" tal:content="lazyvar" />
-        <div tal:condition="bar" tal:content="lazyvar" />
-        <div tal:condition"python: not (foo or bar)">...</div>
-    </div>
-"""
+# BBB
 from zope.tales.expressions import DeferWrapper, DeferExpr
-_marker = object()
-
-# TODO These should really be integrated into the zope.tales implementation
-
-class LazyWrapper(DeferWrapper):
-    """Wrapper for lazy: expression
-    """
-    def __init__(self, expr, econtext):
-        DeferWrapper.__init__(self, expr, econtext)
-        self._result = _marker
-
-    def __call__(self):
-        r = self._result
-        if r is _marker:
-            self._result = r = self._expr(self._econtext)
-        return r
-
-class LazyExpr(DeferExpr):
-    """lazy: expression handler for lazy initialization of expressions
-    """
-    def __call__(self, econtext):
-        return LazyWrapper(self._c, econtext)
-
-    def __repr__(self):
-        return 'lazy:%s' % `self._s`
+from zope.tales.expressions import LazyWrapper, LazyExpr

src/Products/PageTemplates/Expressions.py

@@ -26,6 +26,7 @@ from zope.interface import implements
 from zope.pagetemplate.engine import ZopeEngine as Z3Engine
 from zope.proxy import removeAllProxies
 from zope.tales.expressions import DeferExpr
+from zope.tales.expressions import LazyExpr
 from zope.tales.expressions import NotExpr
 from zope.tales.expressions import PathExpr
 from zope.tales.expressions import StringExpr
@@ -45,7 +46,6 @@ from zExceptions import Unauthorized
 
 from zope.contentprovider.tales import TALESProviderExpression
 from Products.PageTemplates import ZRPythonExpr
-from Products.PageTemplates.DeferExpr import LazyExpr
 from Products.PageTemplates.interfaces import IUnicodeEncodingConflictResolver
 
 SecureModuleImporter = ZRPythonExpr._SecureModuleImporter()

src/Products/PageTemplates/tests/testExpressions.py

@@ -83,18 +83,6 @@ class EngineTestsBase(PlacelessSetup):
         ec = self._makeContext()
         self.failUnless(ec.evaluate('x | nothing') is None)
 
-    def DONT_test_evaluate_with_empty_element(self):
-        # empty path elements aren't supported anymore, for the lack
-        # of a use case
-        ec = self._makeContext()
-        self.assertEqual(ec.evaluate('d/'), 'blank')
-
-    def DONT_test_evaluate_with_empty_element_and_alternative(self):
-        # empty path elements aren't supported anymore, for the lack
-        # of a use case
-        ec = self._makeContext()
-        self.assertEqual(ec.evaluate('d/ | nothing'), 'blank')
-
     def test_evaluate_dict_key_as_underscore(self):
         ec = self._makeContext()
         self.assertEqual(ec.evaluate('d/_'), 'under')
@@ -131,13 +119,13 @@ class EngineTestsBase(PlacelessSetup):
         ec.endScope()
 
     def test_defer_expression_returns_wrapper(self):
-        from Products.PageTemplates.DeferExpr import DeferWrapper
+        from zope.tales.expressions import DeferWrapper
         ec = self._makeContext()
         defer = ec.evaluate('defer: b')
         self.failUnless(isinstance(defer, DeferWrapper))
 
     def test_lazy_expression_returns_wrapper(self):
-        from Products.PageTemplates.DeferExpr import LazyWrapper
+        from zope.tales.expressions import LazyWrapper
         ec = self._makeContext()
         lazy = ec.evaluate('lazy: b')
         self.failUnless(isinstance(lazy, LazyWrapper))
@@ -269,6 +257,3 @@ def test_suite():
          unittest.makeSuite(UnicodeEncodingConflictResolverTests),
          unittest.makeSuite(ZopeContextTests),
     ))
-
-if __name__=='__main__':
-    main()

versions.cfg

@@ -66,7 +66,7 @@ zope.site = 3.9.0
 zope.size = 3.4.1
 zope.structuredtext = 3.4.0
 zope.tal = 3.5.2
-zope.tales = 3.4.0
+zope.tales = 3.5.0
 zope.testbrowser = 3.7.0
 zope.testing = 3.8.3
 zope.traversing = 3.12.0