Fix "Reload Libraries macro issues" (#95)

Reload Libraries macro issues resolved

* Non-KQC elements placed on the layout no longer cause errors

* Better error handling, for example if there are compilation errors in the KQC code

klayout_package/python/kqcircuits/util/layout_to_code.py

@@ -358,31 +358,34 @@ def get_node_params(node: Node):
 
 
 def extract_pcell_data_from_views():
-    """Remove all PCells and return their data.
+    """Iterate over all KQCircuits PCells and return their data and instances.
 
-    Returns: A list of lists. Each element corresponds to a view in KLayout and it is a list of
-        ``(type, location, parameters)`` tuples. These tuples completely describe the type, position and
-        parameters of a single PCell in the "Top Cell" of this view.
+    Returns: a tuple (views, instances) where
+        views: a list of lists. Each element corresponds to a view in KLayout and it is a list of
+        ``(type, location, parameters)`` tuples. These tuples completely describe the type, position
+        and parameters of a single PCell in the "Top Cell" of this view.
+        instances: flattened list of all instances of KQCircuits PCells found.
     """
 
     views = []
+    instances = []
     main_window = pya.Application.instance().main_window()
     for vid in range(main_window.views()):
         top_cell = main_window.view(vid).active_cellview().cell
         pcells = []
         for inst in top_cell.each_inst():
             pc = inst.pcell_declaration()
-            if pc:
+            if isinstance(pc, Element):
+                instances.append(inst)
                 params = inst.pcell_parameters_by_name()
                 def_params = pc.__class__.get_schema()
                 for k, v in def_params.items():
                     if params[k] == v.default:
                         del params[k]
                 pcells.append((pc.__class__, inst.dtrans, params))
-                inst.delete()
         views.append(pcells)
 
-    return views
+    return views, instances
 
 
 def restore_pcells_to_views(views):

klayout_package/python/kqcircuits/util/library_helper.py

@@ -84,6 +84,8 @@ def load_libraries(flush=False, path=""):
     Returns:
          A dictionary of libraries that have been loaded, keys are library names and values are libraries.
     """
+    # Try reloading all pcells before deleting libraries, otherwise classes are lost in case of errors
+    all_pcell_classes = _get_all_pcell_classes(flush, path)
 
     if flush:
         delete_all_libraries()
@@ -95,7 +97,7 @@ def load_libraries(flush=False, path=""):
             if lib_path == path:
                 return {key: value[0] for key, value in _kqc_libraries.items()}
 
-    for cls in _get_all_pcell_classes(flush, path):
+    for cls in all_pcell_classes:
 
         library_name = cls.LIBRARY_NAME
         library_path = cls.LIBRARY_PATH

klayout_package/python/scripts/macros/0system/0reload.lym

@@ -40,8 +40,15 @@ Note that this does not reload the ``defaults`` file.
 from kqcircuits.util.library_helper import load_libraries
 from kqcircuits.util.layout_to_code import extract_pcell_data_from_views, restore_pcells_to_views
 
-views = extract_pcell_data_from_views()
-load_libraries(flush=True)
+views, instances = extract_pcell_data_from_views()
+for inst in instances:
+  inst.delete()
+try:
+  load_libraries(flush=True)
+except Exception as e:
+  restore_pcells_to_views(views)
+  raise RuntimeError("Failed to reload KQCircuits libraries and redraw cells." +
+    f"\nThe following exception was raised: \n{type(e).__name__}: {e}")
 restore_pcells_to_views(views)
 </text>
 </klayout-macro>