From 930f4f3868182f65cf312680bea7feaff67b51ce Mon Sep 17 00:00:00 2001
From: Tanner <git@tanner.vc>
Date: Sat, 7 Nov 2026 23:21:41 +0000
Subject: [PATCH] Clear stale sign data when signs break

---
 mosfet/protocol/managers.py | 15 ++++++++++++-
 mosfet/world.py             | 11 ++++++++++
 tests/test_signs.py         | 42 +++++++++++++++++++++++++++++++++++++
 3 files changed, 67 insertions(+), 1 deletion(-)

diff --git a/mosfet/protocol/managers.py b/mosfet/protocol/managers.py
index d01c40e..94c9c8f 100644
--- a/mosfet/protocol/managers.py
+++ b/mosfet/protocol/managers.py
@@ -283,11 +283,21 @@ class WorldState:
         return chunk.get_block_at(floor(x), floor(y), floor(z))
 
     def set_block_entity(self, position, entity_type, data):
-        self.block_entities[tuple(position)] = {
+        position = tuple(position)
+        if data is None:
+            self.block_entities.pop(position, None)
+            return
+        self.block_entities[position] = {
             'type': entity_type,
             'data': nbt_plain(data),
         }
 
+    @staticmethod
+    def _is_sign_state(block_state_id):
+        from mosfet.info import blocks
+        name = blocks.BLOCKS.get(block_state_id)
+        return name is not None and name.endswith('_sign')
+
     def set_block_at(self, x, y, z, block_state_id):
         x, y, z = floor(x), floor(y), floor(z)
         chunk = self.get_chunk(floor(x / 16), floor(z / 16))
@@ -297,6 +307,9 @@ class WorldState:
         pos = (x, y, z)
         if previous in self.indexed_ids:
             self.index.get(previous, set()).discard(pos)
+        if (self._is_sign_state(previous) and
+                not self._is_sign_state(block_state_id)):
+            self.block_entities.pop(pos, None)
         if block_state_id in self.indexed_ids:
             self.index.setdefault(block_state_id, set()).add(pos)
         return True
diff --git a/mosfet/world.py b/mosfet/world.py
index 1a1fe6d..cff4bfa 100644
--- a/mosfet/world.py
+++ b/mosfet/world.py
@@ -25,6 +25,11 @@ class World:
     def block_at(self, x, y, z):
         return self.g.chunks.get_block_at(x, y, z)
 
+    @staticmethod
+    def _is_sign_state(state_id):
+        name = blocks.BLOCKS.get(state_id)
+        return name is not None and name.endswith('_sign')
+
     @staticmethod
     def _sign_component_text(value):
         if value is None:
@@ -58,6 +63,12 @@ class World:
         for position, entity in self.g.chunks.block_entities.items():
             if utils.phyp(center, position) > distance:
                 continue
+            get_block_at = getattr(self.g.chunks, 'get_block_at', None)
+            if callable(get_block_at):
+                state_id = get_block_at(*position)
+                if (state_id is not None and
+                        not self._is_sign_state(state_id)):
+                    continue
             data = entity.get('data') or {}
             for side in ('front', 'back'):
                 text_data = data.get(side + '_text')
diff --git a/tests/test_signs.py b/tests/test_signs.py
index 39d1605..e3a2baa 100644
--- a/tests/test_signs.py
+++ b/tests/test_signs.py
@@ -3,6 +3,7 @@ from unittest.mock import patch
 from munch import Munch
 
 from mosfet.commands import Commands
+from mosfet.info import blocks
 from mosfet.protocol.managers import EntityManager, WorldState
 from mosfet.world import World
 
@@ -45,6 +46,47 @@ class SignReadingTests(unittest.TestCase):
         signs = World(Munch(chunks=chunks)).find_signs((4, 65, -2), 1)
         self.assertEqual(signs[0]['lines'], ('Farm', '', '', ''))
 
+    def test_broken_sign_block_update_removes_cached_sign_entity(self):
+        position = (4, 65, -2)
+        sign_state = blocks.MCD_BLOCKS['oak_wall_sign']['minStateId']
+
+        class FakeColumn:
+            def __init__(self):
+                self.states = {}
+
+            def get_block_at(self, x, y, z):
+                return self.states.get((x, y, z), blocks.AIR)
+
+            def set_block_at(self, x, y, z, state_id):
+                previous = self.get_block_at(x, y, z)
+                self.states[(x, y, z)] = state_id
+                return previous
+
+        chunks = WorldState()
+        chunks.chunks[(0, -1)] = FakeColumn()
+        chunks.set_block_at(*position, sign_state)
+        chunks.set_block_entity(position, 7, {
+            'front_text': {'messages': ['mosfet1 stay', 'within 8 square', '', '']},
+        })
+        world = World(Munch(chunks=chunks))
+
+        self.assertEqual(len(world.find_signs(position, 1)), 1)
+        chunks.set_block_at(*position, blocks.AIR)
+
+        self.assertNotIn(position, chunks.block_entities)
+        self.assertEqual(world.find_signs(position, 1), [])
+
+    def test_sign_search_ignores_stale_block_entity_for_non_sign_block(self):
+        position = (4, 65, -2)
+        chunks = Munch(
+            block_entities={position: {'data': {'front_text': {
+                'messages': ['mosfet1 stay', 'within 8 square', '', ''],
+            }}}},
+            get_block_at=lambda *_position: blocks.AIR,
+        )
+
+        self.assertEqual(World(Munch(chunks=chunks)).find_signs(position, 1), [])
+
     def test_group_and_individual_sign_addresses(self):
         group_world = World(Munch(chunks=Munch(block_entities={
             (0, 64, 0): {'data': {'front_text': {'messages': [