ZODB Components: Cache source code in the loader to avoid access to ERP5 Site.

Using DeadlockDebugguer lead to a deadlock when trying to debug a deadlock on
ZODB Component as it was trying to load the Component. Moreover, this required
accessing to ERP5 Site whereas DeadlockDebugguer is used outside.

Steps to reproduce:
  1. Create an Extension Component with a sleep and run it.
  2. Call manage_debug_threads.

product/ERP5Type/dynamic/component_package.py

@@ -76,6 +76,7 @@ class ComponentDynamicPackage(ModuleType):
     self._portal_type = portal_type
     self.__version_suffix_len = len('_version')
     self.__registry_dict = collections.defaultdict(dict)
+    self.__fullname_source_code_dict = {}
 
     # Add this module to sys.path for future imports
     sys.modules[namespace] = self
@@ -132,17 +133,14 @@ class ComponentDynamicPackage(ModuleType):
 
   def get_source(self, fullname):
     """
-    Get the source code of the given module name from the ID defined on the
-    dynamic module (setting getTextContent() on the module directly may not
-    work properly upon reset and there is no need for performance there as it
-    is only used for traceback or pdb anyway)
-    """
-    module = __import__(fullname, fromlist=[fullname.rsplit('.', 1)[0]],
-                        level=0)
-
-    component = getSite().unrestrictedTraverse(module.__file__[1:-1])
+    PEP-302 function to get the source code, used mainly by linecache for
+    tracebacks, pdb...
 
-    return component.getTextContent(validated_only=True)
+    Use internal cache rather than accessing the Component directly as this
+    would require accessing ERP5 Site even though the source code may be
+    retrieved outside of ERP5 (eg DeadlockDebugguer).
+    """
+    return self.__fullname_source_code_dict.get(fullname)
 
   def find_module(self, fullname, path=None):
     """
@@ -390,6 +388,9 @@ class ComponentDynamicPackage(ModuleType):
 
       module_cache_set.add(module)
 
+      # Only useful for get_source()
+      self.__fullname_source_code_dict[module_fullname] = source_code_str
+
       return module
     finally:
       # load_module() can be called outside of import machinery, for example
@@ -415,8 +416,9 @@ class ComponentDynamicPackage(ModuleType):
     if sub_package:
       package = sub_package
     else:
-      # Clear the Component registry only once
+      # Clear the Component registry and source code dict only once
       self.__registry_dict.clear()
+      self.__fullname_source_code_dict.clear()
       package = self
 
     for name, module in package.__dict__.items():

product/ERP5Type/patches/python.py

@@ -128,9 +128,9 @@ def patch_linecache():
     display ZODB Components, Python Script source code and TALES Expressions
     properly without requiring to create a temporary file on the filesystem
 
-    The filename is is always '<string>' for any code executed by exec() (ZODB
-    Components), '(FILENAME)?Script \(Python\)' for Zope Python Scripts and
-    'Python Expression "CODE"' for TALES expressions.
+    The filename is is always '<portal_components/*>' for ZODB Components,
+    '(FILENAME)?Script \(Python\)' for Zope Python Scripts and 'Python
+    Expression "CODE"' for TALES expressions.
 
     linecache.cache filled by linecache.updatecache() called by the original
     linecache.getlines() is bypassed for Python Script to avoid getting
@@ -142,7 +142,7 @@ def patch_linecache():
       if module_globals is None:
         module_globals = get_globals(sys._getframe(1))
 
-      # Get source code of ZODB Components (following PEP 302)
+      # Get source code of ZODB Components following PEP 302
       if (filename.startswith('<portal_components/') and
           '__loader__' in module_globals):
         data = None