- Adjusted the "importlater" mechanism, which is

     used internally to resolve import cycles,
     such that the usage of __import__ is completed
     when the import of sqlalchemy or sqlalchemy.orm
     is done, thereby avoiding any usage of __import__
     after the application starts new threads,
     fixes [ticket:2279].  Also in 0.6.9.

5 files changed, 50 insertions, 13 deletions

diff --git a/lib/sqlalchemy/__init__.py b/lib/sqlalchemy/__init__.py
index c15cc6b69..0b9b7a00e 100644
--- a/lib/sqlalchemy/__init__.py
+++ b/lib/sqlalchemy/__init__.py
@@ -120,3 +120,6 @@ __all__ = sorted(name for name, obj in locals().items()
 __version__ = '0.7.3'
 
 del inspect, sys
+
+from sqlalchemy import util as _sa_util
+_sa_util.importlater.resolve_all()
\ No newline at end of file
diff --git a/lib/sqlalchemy/orm/__init__.py b/lib/sqlalchemy/orm/__init__.py
index f6b02eaa8..b7f7884f2 100644
--- a/lib/sqlalchemy/orm/__init__.py
+++ b/lib/sqlalchemy/orm/__init__.py
@@ -1458,3 +1458,6 @@ def undefer_group(name):
 
     """
     return strategies.UndeferGroupOption(name)
+
+from sqlalchemy import util as _sa_util
+_sa_util.importlater.resolve_all()
\ No newline at end of file
diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 893d6ea2a..334d6d378 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -21,7 +21,7 @@ from itertools import chain
 from sqlalchemy import exc as sa_exc
 from sqlalchemy import util
 from sqlalchemy.sql import operators
-deque = util.importlater('collections').deque
+deque = __import__('collections').deque
 
 mapperutil = util.importlater('sqlalchemy.orm', 'util')
 
diff --git a/lib/sqlalchemy/sql/__init__.py b/lib/sqlalchemy/sql/__init__.py
index c591e6802..1b8284781 100644
--- a/lib/sqlalchemy/sql/__init__.py
+++ b/lib/sqlalchemy/sql/__init__.py
@@ -64,3 +64,4 @@ from sqlalchemy.sql.visitors import ClauseVisitor
 
 __tmp = locals().keys()
 __all__ = sorted([i for i in __tmp if not i.startswith('__')])
+
diff --git a/lib/sqlalchemy/util/langhelpers.py b/lib/sqlalchemy/util/langhelpers.py
index 4dd9a5270..cf8b2acac 100644
--- a/lib/sqlalchemy/util/langhelpers.py
+++ b/lib/sqlalchemy/util/langhelpers.py
@@ -527,37 +527,67 @@ class importlater(object):
         from mypackage.somemodule import somesubmod
 
     except evaluted upon attribute access to "somesubmod".
+    
+    importlater() currently requires that resolve_all() be
+    called, typically at the bottom of a package's __init__.py.
+    This is so that __import__ still called only at 
+    module import time, and not potentially within
+    a non-main thread later on.
 
     """
+
+    _unresolved = set()
+
     def __init__(self, path, addtl=None):
         self._il_path = path
         self._il_addtl = addtl
+        importlater._unresolved.add(self)
+
+    @classmethod
+    def resolve_all(cls):
+        for m in list(importlater._unresolved):
+            m._resolve()
+
+    @property
+    def _full_path(self):
+        if self._il_addtl:
+            return self._il_path + "." + self._il_addtl
+        else:
+            return self._il_path
 
     @memoized_property
     def module(self):
+        if self in importlater._unresolved:
+            raise ImportError(
+                    "importlater.resolve_all() hasn't been called")
+
+        m = self._initial_import
         if self._il_addtl:
-            m = __import__(self._il_path, globals(), locals(),
-                                [self._il_addtl])
-            try:
-                return getattr(m, self._il_addtl)
-            except AttributeError:
-                raise ImportError(
-                        "Module %s has no attribute '%s'" %
-                        (self._il_path, self._il_addtl)
-                    )
+            m = getattr(m, self._il_addtl)
         else:
-            m = __import__(self._il_path)
             for token in self._il_path.split(".")[1:]:
                 m = getattr(m, token)
-            return m
+        return m
+
+    def _resolve(self):
+        importlater._unresolved.discard(self)
+        if self._il_addtl:
+            self._initial_import = __import__(
+                                self._il_path, globals(), locals(), 
+                                [self._il_addtl])
+        else:
+            self._initial_import = __import__(self._il_path)
 
     def __getattr__(self, key):
+        if key == 'module':
+            raise ImportError("Could not resolve module %s" 
+                                % self._full_path)
         try:
             attr = getattr(self.module, key)
         except AttributeError:
             raise AttributeError(
                         "Module %s has no attribute '%s'" %
-                        (self._il_path, key)
+                        (self._full_path, key)
                     )
         self.__dict__[key] = attr
         return attr