Mitigation for the exploding phantom tree bug

changelog.txt

@@ -15,6 +15,7 @@ Template for new versions:
 ## New Tools
 
 ## New Features
+- `fix/exploding-trees`: periodically kill trees which have been removed from the map but still exist in the internal list of plants; this prevents them from collapsing once a year.
 
 ## Fixes
 

docs/fix/exploding-trees.rst

@@ -0,0 +1,31 @@
+fix/exploding-trees
+===================
+
+.. dfhack-tool::
+    :summary: Removes "phantom" trees before they can explode.
+    :tags: fort bugfix
+
+By default, this script runs once a month by the Control Panel's Bug Fixes tab.
+
+This script mitigates a longstanding Dwarf Fortress bug.
+
+Once a year, trees check if they should grow.  The exact day and time of this
+growth is different for every tree.
+
+Occasionally, when a tree is cut down or otherwise removed from the game, the
+game engine doesn't remove the tree's data from the list of plants.  The exact
+details of this are not currently understood.
+
+For some reason, these "phantom" trees will sometimes collapse during this
+growth.  This can stun, injure, or kill units which happen to be near this
+collapse.
+
+This script finds those trees and sets their dead flag, preventing them from
+growing and collapsing.
+
+Usage
+-----
+
+::
+
+    fix/exploding-trees

fix/exploding-trees.lua

@@ -0,0 +1,45 @@
+-- removes "phantom" trees before they can explode.
+--[====[
+fix/exploding-trees
+===================
+
+By default, this script runs once a month by the Control Panel's Bug Fixes tab.
+
+This script mitigates a longstanding Dwarf Fortress bug.
+
+Once a year, trees check if they should grow.  The exact day and time of this
+growth is different for every tree.
+
+Occasionally, when a tree is cut down or otherwise removed from the game, the
+game engine doesn't remove the tree's data from the list of plants.  The exact
+details of this are not currently understood.
+
+For some reason, these "phantom" trees will sometimes collapse during this
+growth.  This can stun, injure, or kill units which happen to be near this
+collapse.
+
+This script finds those trees and sets their dead flag, preventing them from
+growing and collapsing.
+--]====]
+
+function suppress_phantom_exploding_trees()
+    for idx, tree in ipairs(df.global.world.plants.all) do
+        if      not tree.damage_flags.dead
+            and tree.tree_info ~= nil
+            and (tree.type == df.plant_type.DRY_TREE
+                or tree.type == df.plant_type.WET_TREE)
+        then
+            local tt = dfhack.maps.getTileType(tree.pos)
+            local is_trunk = df.tiletype.attrs[tt].material == df.tiletype_material.TREE
+            if not is_trunk then
+                tree.damage_flags.dead = true
+                local announcement = string.format(
+                    "DFHack %s: phantom tree %d at location (%d,%d,%d) suppressed.",
+                    dfhack.current_script_name(), idx, tree.pos.x, tree.pos.y, tree.pos.z)
+                dfhack.printerr(announcement)
+            end
+        end
+    end
+end
+
+suppress_phantom_exploding_trees()

internal/control-panel/registry.lua

@@ -93,6 +93,9 @@ COMMANDS_BY_IDX = {
     {command='fix/general-strike', group='bugfix', mode='repeat', default=true,
         desc='Prevent dwarves from getting stuck and refusing to work.',
         params={'--time', '1', '--timeUnits', 'days', '--command', '[', 'fix/general-strike', '-q', ']'}},
+    {command='fix/kill-exploding-trees', group='bugfix', mode='repeat', default=true,
+        desc='Removes "phantom" trees before they can explode.',
+        params={'--time', '1', '--timeUnits', 'months', '--command', '[', 'fix/exploding-trees', ']'}},
     {command='fix/ownership', group='bugfix', mode='repeat', default=true,
         desc='Fixes instances of units claiming the same item or an item they don\'t own.',
         params={'--time', '1', '--timeUnits', 'days', '--command', '[', 'fix/ownership', ']'}},