Merge pull request malthe#293 from starzel/fix_syntaxwarnings

Fix SyntaxWarnings in Python 3.8 when comparing literals with is

CHANGES.rst

@@ -4,7 +4,8 @@ Changes
 3.7 (unreleased)
 ----------------
 
-...
+- Fix SyntaxWarnings in Python 3.8 resulting from comparing literals with 'is'.
+  See https://github.com/plone/Products.CMFPlone/issues/2890.
 
 3.6.1 (2019-04-01)
 ------------------

src/chameleon/compiler.py

@@ -216,8 +216,8 @@ def func(target):
                           'default'),
                           func_defaults=(None,),
                           source=r"""
-    target = translate(msgid, default=default, domain=__i18n_domain, 
-                       context=__i18n_context, 
+    target = translate(msgid, default=default, domain=__i18n_domain,
+                       context=__i18n_context,
                        target_language=target_language)""")
 
 
@@ -949,7 +949,7 @@ def __init__(self, engine_factory, node, filename, source,
             module = ast.Module([])
             module.body += self.visit(node)
             ast.fix_missing_locations(module)
-            prelude = "__filename = %r" % filename
+            prelude = "__filename = %r\n__default = object()" % filename
             generator = TemplateCodeGenerator(module, source)
             tokens = [
                 Token(source[pos:pos + length], pos, source)

src/chameleon/zpt/template.py

@@ -209,7 +209,7 @@ def builtins(self):
     @property
     def engine(self):
         if self.literal_false:
-            default_marker = ast.Str(s="__default__")
+            default_marker = Builtin("__default")
         else:
             default_marker = Builtin("False")
 
@@ -225,7 +225,7 @@ def expression_parser(self):
 
     def parse(self, body):
         if self.literal_false:
-            default_marker = ast.Str(s="__default__")
+            default_marker = Builtin("__default")
         else:
             default_marker = Builtin("False")