environment,dashboard: generalize multiple defaults, fix HDF5 argument load

artiq/dashboard/experiments.py

@@ -331,6 +331,11 @@ class _ExperimentDock(QtWidgets.QMdiSubWindow):
                          self.expurl, exc_info=True)
             return
         for k, v in overrides.items():
+            # Some values (e.g. scans) may have multiple defaults in a list
+            if ("default" in arginfo[k][0]
+                    and isinstance(arginfo[k][0]["default"], list)):
+                arginfo[k][0]["default"].insert(0, v)
+            else:
                 arginfo[k][0]["default"] = v
         self.manager.initialize_submission_arguments(self.expurl, arginfo)
 

artiq/gui/entries.py

@@ -274,8 +274,10 @@ class _ScanEntry(LayoutWidget):
         }
         if "default" in procdesc:
             defaults = procdesc["default"]
+            if not isinstance(defaults, list):
+                defaults = [defaults]
             state["selected"] = defaults[0]["ty"]
-            for default in defaults:
+            for default in reversed(defaults):
                 ty = default["ty"]
                 if ty == "NoScan":
                     state[ty]["value"] = default["value"]

artiq/language/environment.py

@@ -23,6 +23,10 @@ class DefaultMissing(Exception):
 
 class _SimpleArgProcessor:
     def __init__(self, default=NoDefault):
+        # If default is a list, it means multiple defaults are specified, with
+        # decreasing priority.
+        if isinstance(default, list):
+            raise NotImplementedError
         if default is not NoDefault:
             self.default_value = default
 

artiq/language/scan.py

@@ -166,7 +166,7 @@ class Scannable:
         if global_step is None:
             global_step = scale/10.0
         if default is not NoDefault:
-            if not isinstance(default, (tuple, list)):
+            if not isinstance(default, list):
                 default = [default]
             self.default_values = default
         self.unit = unit