Issue 2180 - [cms] Add support for custom Jinja2 functions

cms/converters.py

Index: cms/converters.py
===================================================================
--- a/cms/converters.py
+++ b/cms/converters.py
@@ -263,31 +263,33 @@ class TemplateConverter(Converter):
       "linkify": self.linkify,
       "toclist": self.toclist,
     }
 
     globals = {
       "get_string": self.get_string,
     }
 
-    for filename in self._params["source"].list_files("filters"):
-      root, ext = os.path.splitext(filename)
-      if ext.lower() != ".py":
-        continue
+    for dirname, dictionary in [("filters", filters), ("globals", globals)]:
+      for filename in self._params["source"].list_files(dirname):
+        root, ext = os.path.splitext(filename)
+        if ext.lower() != ".py":
+          continue
 
-      path = "%s/%s" % ("filters", filename)
-      code = self._params["source"].read_file(path)
-      module = imp.new_module(root.replace("/", "."))
-      exec code in module.__dict__
+        path = "%s/%s" % (dirname, filename)
+        code = self._params["source"].read_file(path)
+        module = imp.new_module(root.replace("/", "."))
+        exec code in module.__dict__
 
-      func = os.path.basename(root)
-      if not hasattr(module, func):
-        raise Exception("Expected function %s not found in filter file %s" % (func, filename))
-      filters[func] = getattr(module, func)
-      filters[func].module_ref = module  # Prevent garbage collection
+        name = os.path.basename(root)
+        if not hasattr(module, name):
+          raise Exception("Expected symbol %s not found in %s file %s" % (name, dirname, filename))
+        dictionary[name] = getattr(module, name)
+        if hasattr(dictionary[name], "__call__"):

[Sebastian Noack, 2015/03/20 16:10:54]

You might want to use the callable() built-in function instead. But how does it
come that this hack is necessary? 

[Wladimir Palant, 2015/03/20 16:21:12]

A function doesn't usually have a reference to its module, and the modules we
load here aren't being added to any global table. So while the functions
themselves aren't garbage collected, the module might - and then the function
will suddenly be unable to access variables or imports from its module.

[Sebastian Noack, 2015/03/20 16:26:54]

Yeah, this actually make sense, since we create the module, as opposed to
importing it where a reference ends up in sys.modules. And since global
variables aren't bound to the closure of the function they get lost if there
isn't a reference to the module anymore. But that is certainly worth a more
verbose comment.

[Wladimir Palant, 2015/03/20 16:42:50]

Done.

+          dictionary[name].module_ref = module  # Prevent garbage collection
 
     self._env = jinja2.Environment(loader=self._SourceLoader(self._params["source"]), autoescape=True)
     self._env.filters.update(filters)
     self._env.globals.update(globals)
 
   def get_html(self, source):
     template = self._env.from_string(source)
     module = template.make_module(self._params)