fix: make sync a no-opt on local data

docs/examples/Measure without a Loop.ipynb

@@ -379,7 +379,8 @@
    },
    "outputs": [],
    "source": [
-    "from toymodel import AModel, MockGates, MockSource, MockMeter, AverageAndRaw, ArrayGetter\n",
+    "from toymodel import AModel, MockGates, MockSource, MockMeter, AverageAndRaw\n",
+    "from qcodes.instrument.mock import ArrayGetter\n",
     "\n",
     "# now create this \"experiment\", note that all these are instruments \n",
     "model = AModel()\n",

docs/examples/toymodel.py

@@ -4,7 +4,7 @@
 
 from qcodes import MockInstrument, MockModel, Parameter, Loop, DataArray
 from qcodes.utils.validators import Numbers
-
+from qcodes.instrument.mock import ArrayGetter
 
 class AModel(MockModel):
     def __init__(self):
@@ -147,36 +147,3 @@ def get(self):
         array = data.arrays[self.measured_param.full_name]
         return (array, array.mean())
 
-
-class ArrayGetter(Parameter):
-    """
-    Example parameter that just returns a single array
-
-    TODO: in theory you can make this same Parameter with
-    name, label & shape (instead of names, labels & shapes) and altered
-    setpoints (not wrapped in an extra tuple) and this mostly works,
-    but when run in a loop it doesn't propagate setpoints to the
-    DataSet. We could track down this bug, but perhaps a better solution
-    would be to only support the simplest and the most complex Parameter
-    forms (ie cases 1 and 5 in the Parameter docstring) and do away with
-    the intermediate forms that make everything more confusing.
-    """
-    def __init__(self, measured_param, sweep_values, delay):
-        name = measured_param.name
-        super().__init__(names=(name,))
-        self._instrument = getattr(measured_param, '_instrument', None)
-        self.measured_param = measured_param
-        self.sweep_values = sweep_values
-        self.delay = delay
-        self.shapes = ((len(sweep_values),),)
-        set_array = DataArray(parameter=sweep_values.parameter,
-                              preset_data=sweep_values)
-        self.setpoints = ((set_array,),)
-        if hasattr(measured_param, 'label'):
-            self.labels = (measured_param.label,)
-
-    def get(self):
-        loop = Loop(self.sweep_values, self.delay).each(self.measured_param)
-        data = loop.run_temp()
-        array = data.arrays[self.measured_param.full_name]
-        return (array,)

qcodes/data/data_set.py

@@ -392,15 +392,7 @@ def sync(self):
         # could find a robust and intuitive way to make modifications to the
         # version on the DataServer from the main copy)
         if not self.is_live_mode:
-            # LOCAL DataSet - just read it in
-            # Compare timestamps to avoid overwriting unsaved data
-            if self.last_store > self.last_write:
-                return True
-            try:
-                self.read()
-            except IOError:
-                # if no files exist, they probably haven't been created yet.
-                pass
+            # LOCAL DataSet - no need to sync just use local data
             return False
             # TODO - for remote live plotting, maybe set some timestamp
             # threshold and call it static after it's been dormant a long time?

qcodes/instrument/mock.py

@@ -3,6 +3,9 @@
 from datetime import datetime
 
 from .base import Instrument
+from .parameter import Parameter
+from qcodes import Loop
+from qcodes.data.data_array import DataArray
 from qcodes.process.server import ServerManager, BaseServer
 from qcodes.utils.nested_attrs import _NoDefault
 
@@ -279,3 +282,36 @@ def _delattr(self, attr):
         See NestedAttrAccess for details.
         """
         self.ask('method_call', 'delattr', attr)
+
+class ArrayGetter(Parameter):
+    """
+    Example parameter that just returns a single array
+
+    TODO: in theory you can make this same Parameter with
+    name, label & shape (instead of names, labels & shapes) and altered
+    setpoints (not wrapped in an extra tuple) and this mostly works,
+    but when run in a loop it doesn't propagate setpoints to the
+    DataSet. We could track down this bug, but perhaps a better solution
+    would be to only support the simplest and the most complex Parameter
+    forms (ie cases 1 and 5 in the Parameter docstring) and do away with
+    the intermediate forms that make everything more confusing.
+    """
+    def __init__(self, measured_param, sweep_values, delay):
+        name = measured_param.name
+        super().__init__(names=(name,))
+        self._instrument = getattr(measured_param, '_instrument', None)
+        self.measured_param = measured_param
+        self.sweep_values = sweep_values
+        self.delay = delay
+        self.shapes = ((len(sweep_values),),)
+        set_array = DataArray(parameter=sweep_values.parameter,
+                              preset_data=sweep_values)
+        self.setpoints = ((set_array,),)
+        if hasattr(measured_param, 'label'):
+            self.labels = (measured_param.label,)
+
+    def get(self):
+        loop = Loop(self.sweep_values, self.delay).each(self.measured_param)
+        data = loop.run_temp()
+        array = data.arrays[self.measured_param.full_name]
+        return (array,)

qcodes/tests/test_loop.py

@@ -13,6 +13,7 @@
 from qcodes.data.io import DiskIO
 from qcodes.data.data_array import DataArray
 from qcodes.data.manager import get_data_manager
+from qcodes.instrument.mock import ArrayGetter
 from qcodes.instrument.parameter import Parameter, ManualParameter
 from qcodes.process.helpers import kill_processes
 from qcodes.process.qcodes_process import QcodesProcess
@@ -79,7 +80,7 @@ def test_background_and_datamanager(self):
         # you can only do in-memory loops if you set data_manager=False
         # TODO: this is the one place we don't do quiet=True - test that we
         # really print stuff?
-        data = self.loop.run(location=self.location, background=True)
+        data = self.loop.run(location=self.location, background=True, data_manager=True)
         self.check_empty_data(data)
 
         # wait for process to finish (ensures that this was run in the bg,
@@ -118,6 +119,9 @@ def test_local_instrument(self):
         self.check_loop_data(data)
 
     def test_background_no_datamanager(self):
+        # We don't support syncing data from a background process
+        # if not using a datamanager. See warning in ActiveLoop.run()
+        # So we expect the data to be empty even after running.
         data = self.loop.run(location=self.location,
                              background=True,
                              data_manager=False,
@@ -127,7 +131,7 @@ def test_background_no_datamanager(self):
         self.loop.process.join()
 
         data.sync()
-        self.check_loop_data(data)
+        self.check_empty_data(data)
 
     def test_foreground_and_datamanager(self):
         data = self.loop.run(location=self.location, background=False,
@@ -202,6 +206,16 @@ def test_enqueue(self):
         loop.run_temp()
         self.assertFalse(hasattr(loop, 'process'))
 
+    def test_sync_no_overwrite(self):
+        # Test fix for 380, this tests that the setpoints are not incorrectly
+        # overwritten by data_set.sync() for this to happen with the original code
+        # the delay must be larger than the write period otherwise sync is a no opt.
+
+        loop = Loop(self.gates.chan1.sweep(0, 1, 1), delay=0.1).each(ArrayGetter(self.meter.amplitude,
+                                                                                 self.gates.chan2[0:1:1], 0.000001))
+        data = loop.get_data_set(name='testsweep', write_period=0.01)
+        _ = loop.with_bg_task(data.sync).run()
+        assert not np.isnan(data.chan2).any()
 
 def sleeper(t):
     time.sleep(t)