issue2551026: template variable not defined even though it is.

Fix issue where variables defined in TAL expression are not
available in the scope of the definition. (Tom Ekberg (tekberg))

Author: rouilj

CHANGES.txt

@@ -109,6 +109,9 @@ Fixed:
   found/404. Reported by hannob at
   https://github.com/python/bugs.python.org/issues/34, issue opened by
   JulienPalard.
+- issue2551026: template variable not defined even though it is.
+  Fix issue where variables defined in TAL expression are not
+  available in the scope of the definition. (Tom Ekberg (tekberg))
 
 2018-07-13 1.6.0
 

roundup/cgi/PageTemplates/PythonExpr.py

@@ -17,6 +17,8 @@
 """Generic Python Expression Handler
 """
 
+import symtable
+
 from .TALES import CompilerError
 from sys import exc_info
 
@@ -31,7 +33,8 @@ def __init__(self, name, expr, engine):
         self.expr = expr = expr.strip().replace('\n', ' ')
         try:
             d = {}
-            exec('def f():\n return %s\n' % expr.strip(), d)
+            self.f_code = 'def f():\n return %s\n' % expr.strip()
+            exec(self.f_code, d)
             self._f = d['f']
         except:
             raise CompilerError(('Python expression error:\n'
@@ -40,17 +43,38 @@ def __init__(self, name, expr, engine):
 
     def _get_used_names(self):
         self._f_varnames = vnames = []
-        for vname in self._f.__code__.co_names:
-            if vname[0] not in '$_':
+        for vname in self._get_from_symtab():
+            if vname[0] not in '$_.':
                 vnames.append(vname)
 
+    def _get_from_symtab(self):
+        """
+        Get the variables used in the 'f' function.
+        """
+        variables = set()
+        table = symtable.symtable(self.f_code, "<string>", "exec")
+        if table.has_children():
+            variables.update(self._walk_children(table))
+        return variables
+
+    def _walk_children(self, sym):
+        """
+        Get the variables at this level. Recurse to get them all.
+        """
+        variables = set()
+        for child in sym.get_children():
+            variables.update(set(child.get_identifiers()))
+            if child.has_children():
+                variables.update(self._walk_children(child))
+        return variables
+
     def _bind_used_names(self, econtext, _marker=[]):
         # Bind template variables
         names = {'CONTEXTS': econtext.contexts}
-        vars = econtext.vars
+        variables = econtext.vars
         getType = econtext.getCompiler().getTypes().get
         for vname in self._f_varnames:
-            val = vars.get(vname, _marker)
+            val = variables.get(vname, _marker)
             if val is _marker:
                 has = val = getType(vname)
                 if has:

test/test_pythonexpr.py

@@ -0,0 +1,30 @@
+"""
+In Python 3, sometimes TAL "python:" expressions that refer to
+variables but not all variables are recognized. That is in Python 2.7
+all variables used in a TAL "python:" expression are recognized as
+references. In Python 3.5 (perhaps earlier), some TAL "python:"
+expressions refer to variables but the reference generates an error
+like this:
+
+<class 'NameError'>: name 'some_tal_variable' is not defined
+
+even when the variable is defined. Output after this message lists the
+variable and its value.
+"""
+
+import unittest
+
+from roundup.cgi.PageTemplates.PythonExpr import PythonExpr as PythonExprClass
+
+class ExprTest(unittest.TestCase):
+    def testExpr(self):
+        expr = '[x for x in context.assignedto ' \
+               'if x.realname not in user_realnames]'
+        pe = PythonExprClass('test', expr, None)
+        # Looking at the expression, only context and user_realnames are
+        # external variables. The names assignedto and realname are members,
+        # and x is local.
+        required_names = ['context', 'user_realnames']
+        got_names = pe._f_varnames
+        for required_name in required_names:
+            self.assertIn(required_name, got_names)