Merge PR #602: fix: prevent data loss in clipboard PNG conversion when ImageMagick fails

Authored by 0xbyt4. Only deletes temp .bmp after confirmed successful conversion, restores original on failure. Adds 3 tests.

hermes_cli/clipboard.py

@@ -292,9 +292,12 @@ def _convert_to_png(path: Path) -> bool:
             ["convert", str(tmp), "png:" + str(path)],
             capture_output=True, timeout=5,
         )
-        tmp.unlink(missing_ok=True)
         if r.returncode == 0 and path.exists() and path.stat().st_size > 0:
+            tmp.unlink(missing_ok=True)
             return True
+        else:
+            # Convert failed — restore the original file
+            tmp.rename(path)
     except FileNotFoundError:
         logger.debug("ImageMagick not installed — cannot convert BMP to PNG")
         if tmp.exists() and not path.exists():

tests/tools/test_clipboard.py

@@ -558,6 +558,51 @@ class TestConvertToPng:
                 assert result is True
                 assert dest.exists() and dest.stat().st_size > 0
 
+    def test_imagemagick_failure_preserves_original(self, tmp_path):
+        """When ImageMagick convert fails, the original file must not be lost."""
+        dest = tmp_path / "img.png"
+        original_data = FAKE_BMP
+        dest.write_bytes(original_data)
+
+        def fake_run_fail(cmd, **kw):
+            # Simulate convert failing without producing output
+            return MagicMock(returncode=1)
+
+        with patch.dict(sys.modules, {"PIL": None, "PIL.Image": None}):
+            with patch("hermes_cli.clipboard.subprocess.run", side_effect=fake_run_fail):
+                _convert_to_png(dest)
+
+        # Original file must still exist with original content
+        assert dest.exists(), "Original file was lost after failed conversion"
+        assert dest.read_bytes() == original_data
+
+    def test_imagemagick_not_installed_preserves_original(self, tmp_path):
+        """When ImageMagick is not installed, the original file must not be lost."""
+        dest = tmp_path / "img.png"
+        original_data = FAKE_BMP
+        dest.write_bytes(original_data)
+
+        with patch.dict(sys.modules, {"PIL": None, "PIL.Image": None}):
+            with patch("hermes_cli.clipboard.subprocess.run", side_effect=FileNotFoundError):
+                _convert_to_png(dest)
+
+        assert dest.exists(), "Original file was lost when ImageMagick not installed"
+        assert dest.read_bytes() == original_data
+
+    def test_imagemagick_timeout_preserves_original(self, tmp_path):
+        """When ImageMagick times out, the original file must not be lost."""
+        import subprocess
+        dest = tmp_path / "img.png"
+        original_data = FAKE_BMP
+        dest.write_bytes(original_data)
+
+        with patch.dict(sys.modules, {"PIL": None, "PIL.Image": None}):
+            with patch("hermes_cli.clipboard.subprocess.run", side_effect=subprocess.TimeoutExpired("convert", 5)):
+                _convert_to_png(dest)
+
+        assert dest.exists(), "Original file was lost after timeout"
+        assert dest.read_bytes() == original_data
+
 
 # ── has_clipboard_image dispatch ─────────────────────────────────────────