Trying to simplify custom import.

gluon/custom_import.py

@@ -25,6 +25,9 @@ def track_changes(track=True):
 def is_tracking_changes():
     return TRACK_CHANGES
 
+class CustomImportException(ImportError):
+    pass
+
 def custom_importer(name, globals=None, locals=None, fromlist=None, level=-1):
     """
     The web2py custom importer. Like the standard Python importer but it
@@ -44,6 +47,7 @@ def custom_importer(name, globals=None, locals=None, fromlist=None, level=-1):
             and level<=0 \
             and not name.split('.')[0] in INVALID_MODULES \
             and isinstance(globals, dict):
+        import_tb = None
         try:
             items = current.request.folder.split(os.path.sep)
             if not items[-1]: items = items[:-1]
@@ -52,22 +56,26 @@ def custom_importer(name, globals=None, locals=None, fromlist=None, level=-1):
                 # import like "import x" or "import x.y"
                 result = None
                 for itemname in name.split("."):
-                    new_mod = base_importer(
-                        modules_prefix, globals,locals, [itemname], level)
-                    try:
-                        result = result or new_mod.__dict__[itemname]
-                    except KeyError, e:
-                        raise ImportError, 'Cannot import module %s' % str(e)
                     modules_prefix += "." + itemname
+                    base_importer(
+                         modules_prefix, globals,locals, [], level)
                 return result
             else:
                 # import like "from x import a, b, ..."
                 pname = modules_prefix + "." + name
                 return base_importer(pname, globals, locals, fromlist, level)
         except ImportError, e1:
-            pass # the module does not exist
+            import_tb = sys.exc_info()[2]
+            try:
+                return NAIVE_IMPORTER(name,globals,locals,fromlist,level)
+            except ImportError, e3:
+                raise ImportError, e1, import_tb.tb_next # there an import error in the module
         except Exception, e2:
             raise e2 # there is an error in the module
+        finally:
+            if import_tb:
+                import_tb = None
+
     return NAIVE_IMPORTER(name,globals,locals,fromlist,level)