Feature: Allow selection of compression type and and level during export (#13661)

* Feature: Allow configuring the compression type and compression levels during export

Building on the zip export improvements, this now allows users to further configure the
zip to fit their needs.  A simple stored zip for speed, or a high compression zstd for
the smallest archive.  Full validation of the method and levels at the command line

Co-authored-by: shamoon <4887959+shamoon@users.noreply.github.com>

src/documents/tests/export/test_compression.py

@@ -0,0 +1,208 @@
+import sys
+import zipfile
+
+import pytest
+import pytest_mock
+
+from documents.export import compression
+
+
+class TestCompressionMethods:
+    def test_choices_always_include_zstd(self) -> None:
+        """
+        GIVEN:
+            - The compression policy module's CLI choices list
+        WHEN:
+            - Read on any runtime
+        THEN:
+            - zstd is always present; availability is checked separately so
+              argparse never hides it based on the current Python version
+        """
+        assert compression.COMPRESSION_CHOICES == (
+            "stored",
+            "deflated",
+            "bzip2",
+            "lzma",
+            "zstd",
+        )
+
+    @pytest.mark.parametrize(
+        ("name", "constant"),
+        [
+            ("stored", zipfile.ZIP_STORED),
+            ("deflated", zipfile.ZIP_DEFLATED),
+            ("bzip2", zipfile.ZIP_BZIP2),
+            ("lzma", zipfile.ZIP_LZMA),
+        ],
+    )
+    def test_method_maps_to_zipfile_constant(self, name: str, constant: int) -> None:
+        """
+        GIVEN:
+            - A compression method name
+        WHEN:
+            - Looked up in COMPRESSION_METHODS
+        THEN:
+            - It maps to the matching zipfile compression constant
+        """
+        assert compression.COMPRESSION_METHODS[name] == constant
+
+    def test_stored_and_deflated_always_available(self) -> None:
+        """
+        GIVEN:
+            - The stored and deflated compression methods
+        WHEN:
+            - Checked with compression_available()
+        THEN:
+            - Both are always available (zlib is a hard CPython dependency)
+        """
+        assert compression.compression_available("stored")
+        assert compression.compression_available("deflated")
+
+    def test_zstd_availability_tracks_runtime(self) -> None:
+        """
+        GIVEN:
+            - The zstd compression method
+        WHEN:
+            - Checked with compression_available() on this runtime
+        THEN:
+            - Availability matches whether Python is 3.14+
+        """
+        expected: bool = sys.version_info >= (3, 14)
+        assert compression.compression_available("zstd") == expected
+
+    def test_unimportable_module_reports_unavailable(
+        self,
+        mocker: pytest_mock.MockerFixture,
+    ) -> None:
+        """
+        GIVEN:
+            - A compression method whose backing module fails to import
+              (e.g. a minimal Python build without bz2/lzma compiled in)
+        WHEN:
+            - Checked with compression_available()
+        THEN:
+            - False is returned rather than the ImportError propagating
+        """
+        mocker.patch(
+            "documents.export.compression.importlib.import_module",
+            side_effect=ImportError,
+        )
+        assert not compression.compression_available("bzip2")
+
+
+class TestLevelError:
+    @pytest.mark.parametrize(
+        ("method", "level"),
+        [
+            ("deflated", 0),
+            ("deflated", 9),
+            ("bzip2", 1),
+            ("bzip2", 9),
+            ("zstd", -22),
+            ("zstd", 22),
+            ("deflated", None),
+            ("stored", None),
+        ],
+    )
+    def test_valid_levels_return_none(self, method: str, level: int | None) -> None:
+        """
+        GIVEN:
+            - A method and a level within its valid bounds (or no level)
+        WHEN:
+            - Checked with level_error()
+        THEN:
+            - No error message is returned
+        """
+        assert compression.level_error(method, level) is None
+
+    @pytest.mark.parametrize(
+        ("method", "level"),
+        [
+            ("deflated", 10),
+            ("deflated", -1),
+            ("bzip2", 0),
+            ("bzip2", 10),
+            ("zstd", -23),
+            ("zstd", 23),
+        ],
+    )
+    def test_out_of_range_levels_return_message(
+        self,
+        method: str,
+        level: int,
+    ) -> None:
+        """
+        GIVEN:
+            - A method and a level outside its valid bounds
+        WHEN:
+            - Checked with level_error()
+        THEN:
+            - An error message naming the valid range is returned
+        """
+        msg: str | None = compression.level_error(method, level)
+        assert msg is not None
+        assert "between" in msg
+
+    @pytest.mark.parametrize("method", ["stored", "lzma"])
+    def test_level_on_levelless_method_is_rejected(self, method: str) -> None:
+        """
+        GIVEN:
+            - A method that ignores compression level (stored, lzma)
+        WHEN:
+            - A level is passed to level_error() anyway
+        THEN:
+            - An error message noting the level has no effect is returned
+        """
+        msg: str | None = compression.level_error(method, 5)
+        assert msg is not None
+        assert "no effect" in msg
+
+
+class TestCompressTypeReadable:
+    @pytest.mark.parametrize("ct", [zipfile.ZIP_STORED, zipfile.ZIP_DEFLATED])
+    def test_stored_and_deflated_always_readable(self, ct: int) -> None:
+        """
+        GIVEN:
+            - A stored or deflated compress_type id
+        WHEN:
+            - Checked with compress_type_readable()
+        THEN:
+            - It is always readable
+        """
+        assert compression.compress_type_readable(ct)
+
+    def test_zstd_compress_type_readability_tracks_runtime(self) -> None:
+        """
+        GIVEN:
+            - The zstd compress_type id (93, ZIP_ZSTANDARD)
+        WHEN:
+            - Checked with compress_type_readable() on this runtime
+        THEN:
+            - Readability matches whether Python is 3.14+
+        """
+        expected: bool = sys.version_info >= (3, 14)
+        assert compression.compress_type_readable(93) == expected
+
+    def test_unknown_compress_type_is_unreadable(self) -> None:
+        """
+        GIVEN:
+            - An unrecognized compress_type id
+        WHEN:
+            - Checked with compress_type_readable()
+        THEN:
+            - It is reported as unreadable
+        """
+        assert not compression.compress_type_readable(9999)
+
+    def test_unreadable_method_names_lists_methods(self) -> None:
+        """
+        GIVEN:
+            - A set containing an unknown compress_type id
+        WHEN:
+            - Passed to unreadable_method_names()
+        THEN:
+            - It is reported generically as "method <id>"
+        """
+        # An unknown method id maps to no name and is reported generically.
+        names: set[str] = compression.unreadable_method_names({9999})
+        assert names == {"method 9999"}

src/documents/tests/export/test_sinks.py

@@ -5,6 +5,7 @@ import zipfile
 from pathlib import Path
 
 import pytest
+import pytest_mock
 from pytest_django.fixtures import SettingsWrapper
 
 from documents.export.sinks import DirectoryExportSink
@@ -305,6 +306,48 @@ class TestZipExportSink:
         assert not (target / "export.zip").exists()
 
 
+class TestZipExportSinkCompression:
+    @pytest.mark.parametrize(
+        ("method", "constant"),
+        [
+            ("stored", zipfile.ZIP_STORED),
+            ("deflated", zipfile.ZIP_DEFLATED),
+            ("bzip2", zipfile.ZIP_BZIP2),
+            ("lzma", zipfile.ZIP_LZMA),
+        ],
+    )
+    def test_compression_and_level_forwarded_to_zipfile(
+        self,
+        mocker: pytest_mock.MockerFixture,
+        tmp_path: Path,
+        method: str,
+        constant: int,
+    ) -> None:
+        """
+        GIVEN:
+            - A ZipExportSink constructed with a compression method and level
+        WHEN:
+            - The sink is opened
+        THEN:
+            - zipfile.ZipFile is constructed with those values forwarded
+              unchanged (whether ZipFile actually compresses is Python's own
+              contract, not ours, so this checks the call args, not a real
+              archive)
+        """
+        target: Path = tmp_path / "out"
+        target.mkdir()
+        zip_cls = mocker.patch("documents.export.sinks.zipfile.ZipFile")
+        sink = ZipExportSink(target, "export", compression=constant, compresslevel=5)
+        sink._open()
+        zip_cls.assert_called_once_with(
+            mocker.ANY,
+            "w",
+            compression=constant,
+            compresslevel=5,
+            allowZip64=True,
+        )
+
+
 class TestStreamContract:
     @pytest.fixture(params=["dir", "zip"])
     def sink(self, request: pytest.FixtureRequest, tmp_path: Path) -> ExportSink: