Report .dbz write failures as Error

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

2 files changed, 16 insertions, 4 deletions

diff --git a/generat3d/dbz.py b/generat3d/dbz.py
index a71fbd5..2a56230 100644
--- a/generat3d/dbz.py
+++ b/generat3d/dbz.py
@@ -15,6 +15,7 @@
 # with this program; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 
+import contextlib
 import gzip
 import json
 import math
@@ -22,7 +23,7 @@ import os
 import tempfile
 from pathlib import Path
 
-from . import __version__
+from . import Error, __version__
 from .evaluate import evaluate
 
 
@@ -70,11 +71,16 @@ def build(scene, roots):
 def write(doc, out):
     """Write doc as gzipped JSON. A temp file plus rename: no partial file on failure."""
     out = Path(out)
-    fd, tmp = tempfile.mkstemp(dir=out.parent, prefix=out.name, suffix=".tmp")
+    tmp = None
     try:
+        fd, tmp = tempfile.mkstemp(dir=out.parent, prefix=out.name, suffix=".tmp")
         with os.fdopen(fd, "wb") as f:
             f.write(gzip.compress(json.dumps(doc).encode()))
         os.replace(tmp, out)
-    except BaseException:
-        os.unlink(tmp)
+    except BaseException as e:
+        if tmp is not None:
+            with contextlib.suppress(OSError):
+                os.unlink(tmp)
+        if isinstance(e, OSError):
+            raise Error(f"cannot write {out}: {e.strerror or e}") from None
         raise
diff --git a/tests/test_dbz.py b/tests/test_dbz.py
index 7bcf69a..35c7699 100644
--- a/tests/test_dbz.py
+++ b/tests/test_dbz.py
@@ -24,6 +24,7 @@ import tempfile
 import unittest
 from pathlib import Path
 
+from generat3d import Error
 from generat3d.dbz import build, orientation_quat, write
 from generat3d.library import Library
 from generat3d.scene import load
@@ -77,3 +78,8 @@ class DbzTest(unittest.TestCase):
             with self.assertRaises(TypeError):
                 write({"bad": object()}, out)
             self.assertEqual(list(Path(d).iterdir()), [])
+
+    def test_os_error_becomes_error(self):
+        with tempfile.TemporaryDirectory() as d:
+            with self.assertRaisesRegex(Error, "cannot write"):
+                write(self.doc, Path(d) / "missing" / "s.dbz")