Fix "replace" when moving children in the collection

sdk/python/flet/control.py

@@ -297,7 +297,7 @@ def build_update_commands(self, index, added_controls, commands, isolated=False)
 
         n = 0
         for tag, a1, a2, b1, b2 in sm.get_opcodes():
-            if tag == "delete":
+            if tag == "delete" or tag == "replace":
                 # deleted controls
                 ids = []
                 for h in previous_ints[a1:a2]:
@@ -321,6 +321,23 @@ def build_update_commands(self, index, added_controls, commands, isolated=False)
                         ids.append(ctrl.__uid)
                 if len(ids) > 0:
                     commands.append(Command(0, "remove", ids))
+                if tag == "replace":
+                    # add
+                    for h in current_ints[b1:b2]:
+                        ctrl = hashes[h]
+                        innerCmds = ctrl._build_add_commands(
+                            index=index, added_controls=added_controls
+                        )
+                        assert self.__uid is not None
+                        commands.append(
+                            Command(
+                                indent=0,
+                                name="add",
+                                attrs={"to": self.__uid, "at": str(n)},
+                                commands=innerCmds,
+                            )
+                        )
+                        n += 1
             elif tag == "equal":
                 # unchanged control
                 for h in previous_ints[a1:a2]:
@@ -329,30 +346,6 @@ def build_update_commands(self, index, added_controls, commands, isolated=False)
                         index, added_controls, commands, isolated=ctrl._is_isolated()
                     )
                     n += 1
-            elif tag == "replace":
-                ids = []
-                for h in previous_ints[a1:a2]:
-                    # delete
-                    ctrl = hashes[h]
-                    self._remove_control_recursively(index, ctrl)
-                    ids.append(ctrl.__uid)
-                commands.append(Command(0, "remove", ids))
-                for h in current_ints[b1:b2]:
-                    # add
-                    ctrl = hashes[h]
-                    innerCmds = ctrl._build_add_commands(
-                        index=index, added_controls=added_controls
-                    )
-                    assert self.__uid is not None
-                    commands.append(
-                        Command(
-                            indent=0,
-                            name="add",
-                            attrs={"to": self.__uid, "at": str(n)},
-                            commands=innerCmds,
-                        )
-                    )
-                    n += 1
             elif tag == "insert":
                 # add
                 for h in current_ints[b1:b2]:

sdk/python/tests/test_moving_children.py

@@ -0,0 +1,41 @@
+import random
+
+import flet as ft
+
+
+def test_moving_children():
+    c = ft.Stack()
+    c._Control__uid = "0"
+    for i in range(0, 10):
+        c.controls.append(ft.Container())
+        c.controls[i]._Control__uid = f"_{i}"
+
+    index = []
+    added_controls = []
+    commands = []
+    c.build_update_commands(index, added_controls, commands, False)
+
+    def replace_controls(c):
+        random.shuffle(c.controls)
+        commands.clear()
+
+        # print("=======")
+        r = set()
+        for ctrl in c.controls:
+            # print(ctrl._Control__uid)
+            r.add(ctrl._Control__uid)
+        c.build_update_commands(index, added_controls, commands, False)
+        for cmd in commands:
+            if cmd.name == "add":
+                for sub_cmd in cmd.commands:
+                    # print("add", sub_cmd.attrs["id"], "at", cmd.attrs["at"])
+                    r.add(sub_cmd.attrs["id"])
+            elif cmd.name == "remove":
+                for v in cmd.values:
+                    # print("remove", v)
+                    r.remove(v)
+        # print(r)
+        assert len(r) == len(c.controls)
+
+    for i in range(0, 20):
+        replace_controls(c)