Feature: importer rejects archives with unreadable compression

src/documents/management/commands/document_importer.py

@@ -32,6 +32,8 @@ from django.db.models.signals import post_save
 from filelock import FileLock
 from guardian.shortcuts import clear_ct_cache
 
+from documents.export.compression import compress_type_readable
+from documents.export.compression import unreadable_method_names
 from documents.file_handling import create_source_path_directory
 from documents.management.commands.base import PaperlessCommand
 from documents.management.commands.mixins import CryptMixin
@@ -460,6 +462,17 @@ class Command(CryptMixin, PaperlessCommand):
         with tempfile.TemporaryDirectory() as tmp_dir:
             if is_zipfile(self.source):
                 with ZipFile(self.source) as zf:
+                    unsupported = {
+                        info.compress_type
+                        for info in zf.infolist()
+                        if not compress_type_readable(info.compress_type)
+                    }
+                    if unsupported:
+                        names = ", ".join(sorted(unreadable_method_names(unsupported)))
+                        raise CommandError(
+                            f"This archive uses compression this Python cannot "
+                            f"read ({names}). zstd archives require Python 3.14+.",
+                        )
                     zf.extractall(tmp_dir)
                 self.source = Path(tmp_dir)
             self._run_import()

src/documents/tests/test_management_importer.py

@@ -525,6 +525,35 @@ class TestCommandImport(
         self.assertEqual(doc.tags.count(), 1)
         self.assertEqual(doc.tags.first().name, "batch-flush-tag")
 
+    def test_import_rejects_unreadable_compression(self) -> None:
+        """
+        GIVEN:
+            - A zip archive with an entry whose compression this Python can't read
+        WHEN:
+            - Import is attempted
+        THEN:
+            - A CommandError naming the issue is raised, before extraction
+        """
+        import zipfile
+        from unittest import mock
+
+        archive = Path(self.dirs.scratch_dir) / "export.zip"
+        with zipfile.ZipFile(archive, "w") as zf:
+            zf.writestr("manifest.json", "[]")
+
+        with mock.patch(
+            "documents.management.commands.document_importer.compress_type_readable",
+            return_value=False,
+        ):
+            with self.assertRaises(CommandError) as e:
+                call_command(
+                    "document_importer",
+                    str(archive),
+                    "--no-progress-bar",
+                    skip_checks=True,
+                )
+        self.assertIn("compression", str(e.exception))
+
 
 @pytest.mark.management
 @pytest.mark.django_db