Demonstrate issue 1062277 if you serialize the command stack first

[hooke.git] / hooke / curve.py

diff --git a/hooke/curve.py b/hooke/curve.py
index 75fbf75ce2f394bb9d03dcf39e29ca69bf0419ef..5a32e6d59b8cd2e94902f00e8708d4762cffeb98 100644 (file)
--- a/hooke/curve.py
+++ b/hooke/curve.py
@@ -163,6 +163,68 @@ class Curve (object):
     Another important attribute is :attr:`command_stack`, which holds
     a :class:`~hooke.command_stack.CommandStack` listing the commands
     that have been applied to the `Curve` since loading.
+
+    The data-type is pickleable, to ensure we can move it between
+    processes with :class:`multiprocessing.Queue`\s.
+
+    >>> import pickle
+    >>> import yaml
+    >>> from .engine import CommandMessage
+    >>> c = Curve(path='some/path')
+
+    We add a recursive reference to `c` as you would get from
+    :meth:`hooke.plugin.curve.CurveCommand._add_to_command_stack`.
+
+    >>> c.command_stack.append(CommandMessage('curve info', {'curve':c}))
+
+    >>> s = pickle.dumps(c)
+    >>> z = pickle.loads(s)
+    >>> z
+    <Curve path>
+    >>> z.command_stack[-1].arguments['curve'] == z
+    True
+    >>> print yaml.dump(c)
+    &id001 !!python/object:hooke.curve.Curve
+    command_stack: !!python/object/new:hooke.command_stack.CommandStack
+      listitems:
+      - !!python/object:hooke.engine.CommandMessage
+        arguments:
+          curve: *id001
+        command: curve info
+    data: null
+    driver: null
+    info: {}
+    name: path
+    path: some/path
+    <BLANKLINE>
+
+    However, if we try and serialize the command stack first, we run
+    into `Python issue 1062277`_.
+
+    .. _Python issue 1062277: http://bugs.python.org/issue1062277
+
+    >>> pickle.dumps(c.command_stack)
+    Traceback (most recent call last):
+      ...
+        assert id(obj) not in self.memo
+    AssertionError
+
+    YAML still works, though.
+
+    >>> print yaml.dump(c.command_stack)
+    &id001 !!python/object/new:hooke.command_stack.CommandStack
+    listitems:
+    - !!python/object:hooke.engine.CommandMessage
+      arguments:
+        curve: !!python/object:hooke.curve.Curve
+          command_stack: *id001
+          data: null
+          driver: null
+          info: {}
+          name: path
+          path: some/path
+      command: curve info
+    <BLANKLINE>
     """
     def __init__(self, path, info=None):
         #the data dictionary contains: {name of data: list of data sets [{[x], [y]}]
@@ -192,38 +254,14 @@ class Curve (object):
 
     def __getstate__(self):
         state = dict(self.__dict__)      # make a copy of the attribute dict.
-        state['info'] = dict(self.info)  # make a copy of the info dict too.
         del(state['_hooke'])
-        dc = state['command_stack']
-        if hasattr(dc, '__getstate__'):
-            state['command_stack'] = dc.__getstate__()
-        if state['info'].get('experiment', None) != None:
-            e = state['info']['experiment']
-            assert isinstance(e, experiment.Experiment), type(e)
-            # HACK? require Experiment classes to be defined in the
-            # experiment module.
-            state['info']['experiment'] = e.__class__.__name__
         return state
 
     def __setstate__(self, state):
         self.name = self._hooke = None
         for key,value in state.items():
-            if key == 'path':
-                self.set_path(value)
-                continue
-            elif key == 'info':
-                if 'experiment' not in value:
-                    value['experiment'] = None
-                elif value['experiment'] != None:
-                    # HACK? require Experiment classes to be defined in the
-                    # experiment module.
-                    cls = getattr(experiment, value['experiment'])
-                    value['experiment'] = cls()
-            elif key == 'command_stack':
-                v = CommandStack()
-                v.__setstate__(value)
-                value = v
             setattr(self, key, value)
+        self.set_path(state.get('path', None))
 
     def set_hooke(self, hooke=None):
         if hooke != None: