Merge branch '2819-add-scan-property-to-sequence-object' into 'master'

Resolve "add scan property to sequence object"

Closes #2819

See merge request bliss/bliss!3794

bliss/scanning/group.py

@@ -140,7 +140,7 @@ class Sequence:
 
     def __init__(self, scan_info=None, title="sequence_of_scans"):
         self.title = title
-        self.scan = None
+        self._scan = None
         self._scan_info = ScanInfo.normalize(scan_info)
         self._scan_info["is-scan-sequence"] = True
         self.custom_channels = dict()
@@ -161,7 +161,6 @@ class Sequence:
 
     @contextmanager
     def sequence_context(self):
-        self._build_scan()
 
         group_scan = gevent.spawn(self.scan.run)
 
@@ -228,8 +227,14 @@ class Sequence:
         else:
             self.group_custom_slave = None
 
-        self.scan = ScanGroup(chain, self.title, save=True, scan_info=self._scan_info)
-        self.scan.add_preset(StatePreset(self))
+        self._scan = ScanGroup(chain, self.title, save=True, scan_info=self._scan_info)
+        self._scan.add_preset(StatePreset(self))
+
+    @property
+    def scan(self):
+        if self._scan is None:
+            self._build_scan()
+        return self._scan
 
     @property
     def node(self):
@@ -242,14 +247,14 @@ class Sequence:
         Which is the initial one, or the one published by the scan which publish
         this sequence.
         """
-        if self.scan is None:
+        if self._scan is None:
             return self._scan_info
         else:
             self.scan.scan_info
 
     @property
     def state(self):
-        if self.scan is None:
+        if self._scan is None:
             return ScanState.IDLE
         else:
             return self.scan.state

tests/scans/test_sequence.py

@@ -19,6 +19,7 @@ from bliss.scanning.chain import AcquisitionChannel
 from bliss.data.node import get_session_node
 from bliss import current_session
 from bliss.scanning.scan import ScanState
+from bliss.scanning.acquisition.calc import CalcChannelAcquisitionSlave
 
 
 def test_sequence_terminated_scans(session):
@@ -443,3 +444,27 @@ def test_sequence_issue_2752(session, scan_meta):
         with seq.sequence_context() as ctx:
             pass
     assert "Failed to prepare scan sequence" in str(excinfo)
+
+
+def test_sequence_create_scan_before_running(session):
+
+    diode = session.config.get("diode")
+
+    seq = Sequence()
+    scan = seq.scan
+    calc = CalcChannelAcquisitionSlave("", [], None, [])
+    scan.acq_chain.add(seq.group_acq_master, calc)
+
+    nodes_before_running = scan.acq_chain.nodes_list
+
+    with seq.sequence_context() as seq_context:
+        s1 = scans.loopscan(20, .1, diode, run=False)
+        seq_context.add(s1)
+        g1 = gevent.spawn(s1.run)
+
+        gevent.joinall([g1], raise_error=True)
+
+    nodes_after_running = seq.scan.acq_chain.nodes_list
+
+    # check that scan sequence does not have been recreated with sequence context
+    assert nodes_before_running == nodes_after_running