[Checkins] SVN: z3c.pt/trunk/ Added dynamic scope support for dynamic path- and exists-methods (rarely used).

[Malthe Borch]

Log message for revision 96695:
  Added dynamic scope support for dynamic path- and exists-methods (rarely used).

Changed:
  U   z3c.pt/trunk/CHANGES.txt
  U   z3c.pt/trunk/src/z3c/pt/pagetemplate.py

-=-
Modified: z3c.pt/trunk/CHANGES.txt
===================================================================
--- z3c.pt/trunk/CHANGES.txt	2009-02-18 12:33:03 UTC (rev 96694)
+++ z3c.pt/trunk/CHANGES.txt	2009-02-18 13:18:54 UTC (rev 96695)
@@ -1,6 +1,10 @@
 Changelog
 ---------
 
+- When evaluating path-expressions at runtime (e.g. the ``path``
+  method), run the source through the transform first to support
+  dynamic scope. [malthe]
+
 Version 1.0b8 - February 17, 2009
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 

Modified: z3c.pt/trunk/src/z3c/pt/pagetemplate.py
===================================================================
--- z3c.pt/trunk/src/z3c/pt/pagetemplate.py	2009-02-18 12:33:03 UTC (rev 96694)
+++ z3c.pt/trunk/src/z3c/pt/pagetemplate.py	2009-02-18 13:18:54 UTC (rev 96695)
@@ -1,11 +1,13 @@
 import os
 import sys
+import compiler
 
 from zope import i18n
 from zope import component
 
 from chameleon.core import types
 from chameleon.core import config
+from chameleon.core import codegen
 from chameleon.core import clauses
 from chameleon.core import generation
 
@@ -19,10 +21,9 @@
 
 def evaluate_expression(pragma, expr):
     key = "%s(%s)" % (pragma, expr)
-    cache = getattr(_expr_cache, key, _marker)
-    if cache is not _marker:
-        symbol_mapping, parts, source = cache
-    else:
+    try:
+        symbol_mapping, parts, source = _expr_cache[key]
+    except KeyError:
         translator = component.getUtility(IExpressionTranslator, name=pragma)
         parts = translator.tales(expr)
         stream = generation.CodeIO(symbols=config.SYMBOLS)
@@ -46,10 +47,22 @@
             raise RuntimeError, "Can't locate template frame."
 
     _locals = frame.f_locals
-    _locals.update(symbol_mapping)    
+    _locals.update(symbol_mapping)
+    
+    # to support dynamic scoping (like in templates), we must
+    # transform the code to take the scope locals into account; for
+    # efficiency, this is cached for reuse
+    code_cache_key = key, tuple(_locals)
+    try:
+        code = _expr_cache[code_cache_key]
+    except KeyError:
+        suite = codegen.Suite(source, _locals)
+        code = compiler.compile(
+            suite.source, 'dynamic_path_expression.py', 'exec')
+        _expr_cache[code_cache_key] = code
 
     # execute code and return evaluation
-    exec source in _locals
+    exec code in codegen.lookup_globals.copy(), _locals
     return _locals['result']
 
 def evaluate_path(expr):