Gracefully handle op creation abort when no TC is available or selected.

src/Mod/Path/PathScripts/PathOp.py

@@ -68,6 +68,13 @@ FeatureDiameters = 0x4000  # Turning Diameters
 
 FeatureBaseGeometry = FeatureBaseVertexes | FeatureBaseFaces | FeatureBaseEdges
 
+class PathNoTCException(Exception):
+    '''PathNoTCException is raised when no TC was selected or matches the input
+    criteria. This can happen intentionally by the user when they cancel the TC
+    selection dialog.'''
+
+    def __init__(self):
+        super().__init__('No Tool Controller found')
 
 class ObjectOp(object):
     """
@@ -568,7 +575,7 @@ class ObjectOp(object):
             else:
                 obj.ToolController = PathUtils.findToolController(obj, self)
             if not obj.ToolController:
-                return None
+                raise PathNoTCException()
             obj.OpToolDiameter = obj.ToolController.Tool.Diameter
 
         if FeatureCoolant & features:

src/Mod/Path/PathScripts/PathOpGui.py

@@ -1388,15 +1388,25 @@ def Create(res):
     this function directly, but calls the Activated() function of the Command object
     that is created in each operations Gui implementation."""
     FreeCAD.ActiveDocument.openTransaction("Create %s" % res.name)
-    obj = res.objFactory(res.name, obj=None, parentJob=res.job)
-    if obj.Proxy:
-        obj.ViewObject.Proxy = ViewProvider(obj.ViewObject, res)
-        obj.ViewObject.Visibility = False
-        FreeCAD.ActiveDocument.commitTransaction()
+    try:
+        obj = res.objFactory(res.name, obj=None, parentJob=res.job)
+        if obj.Proxy:
+            obj.ViewObject.Proxy = ViewProvider(obj.ViewObject, res)
+            obj.ViewObject.Visibility = False
+            FreeCAD.ActiveDocument.commitTransaction()
+
+            obj.ViewObject.Document.setEdit(obj.ViewObject, 0)
+            return obj
+    except PathUtils.PathNoTCExistsException:
+        msg = translate('PathOp', 'No suitable tool controller found.\nAborting op creation')
+        diag = QtGui.QMessageBox(QtGui.QMessageBox.Warning, "Error", msg)
+        diag.setWindowModality(QtCore.Qt.ApplicationModal)
+        diag.exec_()
+    except PathOp.PathNoTCException:
+        PathLog.warning(translate('PathOp', 'No tool controller, aborting op creation'))
 
-        obj.ViewObject.Document.setEdit(obj.ViewObject, 0)
-        return obj
     FreeCAD.ActiveDocument.abortTransaction()
+    FreeCAD.ActiveDocument.recompute()
     return None
 
 

src/Mod/Path/PathScripts/PathUtils.py

@@ -51,6 +51,13 @@ else:
 
 UserInput = None
 
+class PathNoTCExistsException(Exception):
+    '''PathNoECExistsException is raised when no TC exists at all, or when all
+    existing TCs are rejected by a given op.
+    This is typically an error because avery op requires a TC. '''
+
+    def __init__(self):
+        super().__init__('No Tool Controllers exist')
 
 def waiting_effects(function):
     def new_function(*args, **kwargs):
@@ -375,7 +382,7 @@ def findToolController(obj, proxy, name=None):
     controllers = getToolControllers(obj, proxy)
 
     if len(controllers) == 0:
-        return None
+        raise PathNoTCExistsException()
 
     # If there's only one in the job, use it.
     if len(controllers) == 1:
@@ -383,9 +390,9 @@ def findToolController(obj, proxy, name=None):
             tc = controllers[0]
         else:
             tc = None
-    elif name is not None:  # More than one, make the user choose.
+    elif name is not None:
         tc = [i for i in controllers if i.Label == name][0]
-    elif UserInput:
+    elif UserInput:  # More than one, make the user choose.
         tc = UserInput.chooseToolController(controllers)
     return tc