From d2ecf664928fdaf144dab346271e4caa9ed2f241 Mon Sep 17 00:00:00 2001
From: Philipp Oeser <philipp@blender.org>
Date: Wed, 26 Feb 2025 14:14:14 +0100
Subject: [PATCH] Fix #120697: better error for BVHTree.FromObject()

When called on an object that you cannot get a mesh from (e.g. Empties),
you would run into an unhelpful "SystemError: <built-in method
FromObject of type object at ...> returned NULL without setting an
exception"

Now be more specific in the error message.

Pull Request: https://projects.blender.org/blender/blender/pulls/135162
---
 .../python/mathutils/mathutils_bvhtree.cc     | 48 ++++++++++++++++---
 1 file changed, 41 insertions(+), 7 deletions(-)

diff --git a/source/blender/python/mathutils/mathutils_bvhtree.cc b/source/blender/python/mathutils/mathutils_bvhtree.cc
index 2884e3737ff..54b9ab6374e 100644
--- a/source/blender/python/mathutils/mathutils_bvhtree.cc
+++ b/source/blender/python/mathutils/mathutils_bvhtree.cc
@@ -1037,6 +1037,7 @@ static const Mesh *bvh_get_mesh(const char *funcname,
   const CustomData_MeshMasks data_masks = CD_MASK_BAREMESH;
   const bool use_render = DEG_get_mode(depsgraph) == DAG_EVAL_RENDER;
   *r_free_mesh = false;
+  Mesh *mesh;
 
   /* Write the display mesh into the dummy mesh */
   if (use_deform) {
@@ -1049,15 +1050,33 @@ static const Mesh *bvh_get_mesh(const char *funcname,
         return nullptr;
       }
 
+      mesh = blender::bke::mesh_create_eval_final(depsgraph, scene, ob, &data_masks);
+      if (mesh == nullptr) {
+        PyErr_Format(PyExc_ValueError,
+                     "%s(...): Cannot get a mesh from object '%s'",
+                     ob->id.name + 2,
+                     funcname);
+        return nullptr;
+      }
+
       *r_free_mesh = true;
-      return blender::bke::mesh_create_eval_final(depsgraph, scene, ob, &data_masks);
+      return mesh;
     }
     if (ob_eval != nullptr) {
       if (use_cage) {
-        return blender::bke::mesh_get_eval_deform(depsgraph, scene, ob_eval, &data_masks);
+        mesh = blender::bke::mesh_get_eval_deform(depsgraph, scene, ob_eval, &data_masks);
       }
-
-      return BKE_object_get_evaluated_mesh(ob_eval);
+      else {
+        mesh = BKE_object_get_evaluated_mesh(ob_eval);
+      }
+      if (mesh == nullptr) {
+        PyErr_Format(PyExc_ValueError,
+                     "%s(...): Cannot get a mesh from object '%s'",
+                     ob->id.name + 2,
+                     funcname);
+        return nullptr;
+      }
+      return mesh;
     }
 
     PyErr_Format(PyExc_ValueError,
@@ -1075,9 +1094,16 @@ static const Mesh *bvh_get_mesh(const char *funcname,
           funcname);
       return nullptr;
     }
-
+    mesh = blender::bke::mesh_create_eval_no_deform_render(depsgraph, scene, ob, &data_masks);
+    if (mesh == nullptr) {
+      PyErr_Format(PyExc_ValueError,
+                   "%s(...): Cannot get a mesh from object '%s'",
+                   ob->id.name + 2,
+                   funcname);
+      return nullptr;
+    }
     *r_free_mesh = true;
-    return blender::bke::mesh_create_eval_no_deform_render(depsgraph, scene, ob, &data_masks);
+    return mesh;
   }
 
   if (use_cage) {
@@ -1088,8 +1114,16 @@ static const Mesh *bvh_get_mesh(const char *funcname,
     return nullptr;
   }
 
+  mesh = blender::bke::mesh_create_eval_no_deform(depsgraph, scene, ob, &data_masks);
+  if (mesh == nullptr) {
+    PyErr_Format(PyExc_ValueError,
+                 "%s(...): Cannot get a mesh from object '%s'",
+                 ob->id.name + 2,
+                 funcname);
+    return nullptr;
+  }
   *r_free_mesh = true;
-  return blender::bke::mesh_create_eval_no_deform(depsgraph, scene, ob, &data_masks);
+  return mesh;
 }
 
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