Check the sub rules are also valid

refs CORE-6641

Checking the sub rules are also valid we allow to check for different
positions in the chain for the BAG message we need to migrate, because
we don't really know where it should go, and the 'lazy' check for valid
in the make_update_rule method makes the suggested rules pass almost
always, so we can easily get a rule in the wrong place that later would
fail because there are no rules for the sub fields.

tools/rosbag/src/rosbag/migration.py

@@ -968,7 +968,7 @@ def find_path(self, old_class, new_class):
                 found_stop = True
                 break
 
-        # Next see if we can create a valid rule
+        # Next see if we can create a valid rule, including the sub rules
         if not found_stop:
             for (ind, tmp_sn) in reversed(list(zip(range(len(sn_range)), sn_range))):
                 if (tmp_sn.new_class._type != new_class._type):
@@ -977,12 +977,13 @@ def find_path(self, old_class, new_class):
                 R = new_rule(self, 'GENERATED.' + new_rule.__name__)
                 if R.valid:
                     R.find_sub_paths()
-                    sn = ScaffoldNode(tmp_sn.new_class, new_class, R)
-                    self.extra_nodes.append(sn)
-                    sn_range = sn_range[:ind+1]
-                    sn_range.append(sn)
-                    found_stop = True
-                    break
+                    if R.sub_rules_valid:
+                        sn = ScaffoldNode(tmp_sn.new_class, new_class, R)
+                        self.extra_nodes.append(sn)
+                        sn_range = sn_range[:ind+1]
+                        sn_range.append(sn)
+                        found_stop = True
+                        break
 
         # If there were no valid implicit rules, we suggest a new one from to the end
         if not found_stop:
@@ -1018,7 +1019,7 @@ def find_path(self, old_class, new_class):
                     self.found_paths[key] = [sn]
                     return [sn]
 
-        # Next see if we can create a valid rule
+        # Next see if we can create a valid rule, including the sub rules
         if not found_start:
             for (ind, tmp_sn) in reversed(list(zip(range(len(sn_range)), sn_range))):
                 if (tmp_sn.old_class._type != old_class._type):
@@ -1027,12 +1028,13 @@ def find_path(self, old_class, new_class):
                 R = new_rule(self, 'GENERATED.' + new_rule.__name__)
                 if R.valid:
                     R.find_sub_paths()
-                    sn = ScaffoldNode(old_class, tmp_sn.old_class, R)
-                    self.extra_nodes.append(sn)
-                    sn_range = sn_range[ind:]
-                    sn_range.insert(0,sn)
-                    found_start = True
-                    break
+                    if R.sub_rules_valid:
+                        sn = ScaffoldNode(old_class, tmp_sn.old_class, R)
+                        self.extra_nodes.append(sn)
+                        sn_range = sn_range[ind:]
+                        sn_range.insert(0,sn)
+                        found_start = True
+                        break
 
         # If there were no valid implicit rules, we suggest a new one from the beginning
         if not found_start: