Make Items::getPosition exactly match the DF original in behavior.

LUA_API.rst

@@ -693,7 +693,7 @@ Units module
 
 * ``dfhack.units.getPosition(unit)``
 
-  Returns true *x,y,z* of the unit; may be not equal to unit.pos if caged.
+  Returns true *x,y,z* of the unit, or *nil* if invalid; may be not equal to unit.pos if caged.
 
 * ``dfhack.units.getContainer(unit)``
 
@@ -752,7 +752,7 @@ Items module
 
 * ``dfhack.items.getPosition(item)``
 
-  Returns true *x,y,z* of the item; may be not equal to item.pos if in inventory.
+  Returns true *x,y,z* of the item, or *nil* if invalid; may be not equal to item.pos if in inventory.
 
 * ``dfhack.items.getGeneralRef(item, type)``
 

Lua API.html

@@ -935,7 +935,7 @@ a lua list containing them.</p>
 <h3><a class="toc-backref" href="#id16">Units module</a></h3>
 <ul>
 <li><p class="first"><tt class="docutils literal">dfhack.units.getPosition(unit)</tt></p>
-<p>Returns true <em>x,y,z</em> of the unit; may be not equal to unit.pos if caged.</p>
+<p>Returns true <em>x,y,z</em> of the unit, or <em>nil</em> if invalid; may be not equal to unit.pos if caged.</p>
 </li>
 <li><p class="first"><tt class="docutils literal">dfhack.units.getContainer(unit)</tt></p>
 <p>Returns the container (cage) item or <em>nil</em>.</p>
@@ -982,7 +982,7 @@ or raws. The <tt class="docutils literal">ignore_noble</tt> boolean disables the
 <h3><a class="toc-backref" href="#id17">Items module</a></h3>
 <ul>
 <li><p class="first"><tt class="docutils literal">dfhack.items.getPosition(item)</tt></p>
-<p>Returns true <em>x,y,z</em> of the item; may be not equal to item.pos if in inventory.</p>
+<p>Returns true <em>x,y,z</em> of the item, or <em>nil</em> if invalid; may be not equal to item.pos if in inventory.</p>
 </li>
 <li><p class="first"><tt class="docutils literal">dfhack.items.getGeneralRef(item, type)</tt></p>
 <p>Searches for a general_ref with the given type.</p>

library/modules/Items.cpp

@@ -69,6 +69,7 @@ using namespace std;
 #include "df/general_ref_unit_itemownerst.h"
 #include "df/general_ref_contains_itemst.h"
 #include "df/general_ref_contained_in_itemst.h"
+#include "df/vermin.h"
 
 using namespace DFHack;
 using namespace df::enums;
@@ -512,9 +513,12 @@ df::coord Items::getPosition(df::item *item)
 {
     CHECK_NULL_POINTER(item);
 
-    if (item->flags.bits.in_inventory ||
+    /* Function reverse-engineered from DF code. */
-        item->flags.bits.in_chest ||
+
-        item->flags.bits.in_building)
+    if (item->flags.bits.removed)
+        return df::coord();
+
+    if (item->flags.bits.in_inventory)
     {
         for (size_t i = 0; i < item->itemrefs.size(); i++)
         {
@@ -532,15 +536,31 @@ df::coord Items::getPosition(df::item *item)
                     return Units::getPosition(unit);
                 break;
 
-            case general_ref_type::BUILDING_HOLDER:
+            /*case general_ref_type::BUILDING_HOLDER:
                 if (auto bld = ref->getBuilding())
                     return df::coord(bld->centerx, bld->centery, bld->z);
+                break;*/
+
+            default:
                 break;
+            }
+        }
+
+        for (size_t i = 0; i < item->specific_refs.size(); i++)
+        {
+            df::specific_ref *ref = item->specific_refs[i];
+
+            switch (ref->type)
+            {
+            case specific_ref_type::VERMIN_ESCAPED_PET:
+                return ref->vermin->pos;
 
             default:
                 break;
             }
         }
+
+        return df::coord();
     }
 
     return item->pos;
@@ -625,6 +645,10 @@ bool DFHack::Items::moveToContainer(MapExtras::MapCache &mc, df::item *item, df:
     CHECK_NULL_POINTER(item);
     CHECK_NULL_POINTER(container);
 
+    auto cpos = getPosition(container);
+    if (!cpos.isValid())
+        return false;
+
     if (!detachItem(mc, item))
         return false;
 
@@ -635,7 +659,7 @@ bool DFHack::Items::moveToContainer(MapExtras::MapCache &mc, df::item *item, df:
     {
         delete ref1; delete ref2;
         Core::printerr("Could not allocate container refs.\n");
-        putOnGround(mc, item, getPosition(container));
+        putOnGround(mc, item, cpos);
         return false;
     }