Extend default skip magic rather than overwrite it.

tests/test_cli.py

@@ -1,5 +1,5 @@
 from pathlib import Path
-from typing import List, Optional, Type
+from typing import Iterable, List, Optional, Type
 from unittest import mock
 
 import pytest
@@ -10,7 +10,12 @@
 from unblob.extractors.command import MultiFileCommand
 from unblob.handlers import BUILTIN_HANDLERS
 from unblob.models import DirectoryHandler, Glob, Handler, HexString, MultiFile
-from unblob.processing import DEFAULT_DEPTH, DEFAULT_PROCESS_NUM, ExtractionConfig
+from unblob.processing import (
+    DEFAULT_DEPTH,
+    DEFAULT_PROCESS_NUM,
+    DEFAULT_SKIP_MAGIC,
+    ExtractionConfig,
+)
 from unblob.ui import (
     NullProgressReporter,
     ProgressReporter,
@@ -367,3 +372,51 @@ def test_skip_extraction(
     assert (
         process_file_mock.call_args.args[0].skip_extraction == skip_extraction
     ), fail_message
+
+
+@pytest.mark.parametrize(
+    "args, skip_magic, fail_message",
+    [
+        ([], DEFAULT_SKIP_MAGIC, "Should have kept default skip magics"),
+        (
+            ["--skip-magic", "SUPERMAGIC"],
+            (*DEFAULT_SKIP_MAGIC, "SUPERMAGIC"),
+            "Should have kept default skip magics",
+        ),
+        (["--clear-skip-magics"], [], "Should have cleared default skip magics"),
+        (
+            ["--clear-skip-magics", "--skip-magic", "SUPERMAGIC"],
+            ["SUPERMAGIC"],
+            "Should have cleared default skip magics",
+        ),
+        (
+            ["--clear-skip-magics", "--skip-magic", DEFAULT_SKIP_MAGIC[1]],
+            [DEFAULT_SKIP_MAGIC[1]],
+            "Should allow user specified and remove the rest",
+        ),
+    ],
+)
+def test_clear_skip_magics(
+    args: List[str], skip_magic: Iterable[str], fail_message: str, tmp_path: Path
+):
+    runner = CliRunner()
+    in_path = (
+        Path(__file__).parent
+        / "integration"
+        / "archive"
+        / "zip"
+        / "regular"
+        / "__input__"
+        / "apple.zip"
+    )
+    params = [*args, "--extract-dir", str(tmp_path), str(in_path)]
+
+    process_file_mock = mock.MagicMock()
+    with mock.patch.object(unblob.cli, "process_file", process_file_mock):
+        result = runner.invoke(unblob.cli.cli, params)
+
+    assert result.exit_code == 0
+    process_file_mock.assert_called_once()
+    assert sorted(process_file_mock.call_args.args[0].skip_magic) == sorted(
+        skip_magic
+    ), fail_message

unblob/cli.py

@@ -168,9 +168,11 @@ def __init__(
     "--skip-magic",
     "skip_magic",
     type=click.STRING,
-    default=DEFAULT_SKIP_MAGIC,
-    help="Skip processing files with given magic prefix",
-    show_default=True,
+    help=f"""Skip processing files with given magic prefix.
+        The provided values are appended to unblob's own skip magic list unless
+        --clear-skip-magic is provided.
+        [default: {', '.join(DEFAULT_SKIP_MAGIC)}]
+    """,
     multiple=True,
 )
 @click.option(
@@ -182,6 +184,14 @@ def __init__(
     show_default=True,
     multiple=True,
 )
+@click.option(
+    "--clear-skip-magics",
+    "clear_skip_magics",
+    is_flag=True,
+    show_default=True,
+    default=False,
+    help="Clear unblob's own skip magic list.",
+)
 @click.option(
     "-p",
     "--process-num",
@@ -246,6 +256,7 @@ def cli(
     entropy_depth: int,
     skip_magic: Iterable[str],
     skip_extension: Iterable[str],
+    clear_skip_magics: bool,  # noqa: FBT001
     skip_extraction: bool,  # noqa: FBT001
     keep_extracted_chunks: bool,  # noqa: FBT001
     handlers: Handlers,
@@ -263,6 +274,9 @@ def cli(
     extra_dir_handlers = plugin_manager.load_dir_handlers_from_plugins()
     dir_handlers += tuple(extra_dir_handlers)
 
+    extra_magics_to_skip = () if clear_skip_magics else DEFAULT_SKIP_MAGIC
+    skip_magic = tuple(sorted(set(skip_magic).union(extra_magics_to_skip)))
+
     config = ExtractionConfig(
         extract_root=extract_root,
         force_extract=force,

unblob/processing.py

@@ -52,31 +52,31 @@
 DEFAULT_PROCESS_NUM = multiprocessing.cpu_count()
 DEFAULT_SKIP_MAGIC = (
     "BFLT",
-    "JPEG",
+    "Composite Document File V2 Document",
+    "Erlang BEAM file",
     "GIF",
-    "PNG",
-    "SQLite",
-    "compiled Java class",
-    "TrueType Font data",
-    "PDF document",
-    "magic binary file",
-    "MS Windows icon resource",
-    "Web Open Font Format",
     "GNU message catalog",
-    "Xilinx BIT data",
+    "HP Printer Job Language",
+    "Intel serial flash for PCH ROM",
+    "JPEG",
+    "MPEG",
+    "MS Windows icon resource",
+    "Macromedia Flash data",
     "Microsoft Excel",
-    "Microsoft Word",
-    "Microsoft PowerPoint",
     "Microsoft OOXML",
+    "Microsoft PowerPoint",
+    "Microsoft Word",
     "OpenDocument",
-    "Macromedia Flash data",
-    "MPEG",
-    "HP Printer Job Language",
-    "Erlang BEAM file",
-    "python",  # (e.g. python 2.7 byte-compiled)
-    "Composite Document File V2 Document",
+    "PDF document",
+    "PNG",
+    "SQLite",
+    "TrueType Font data",
+    "Web Open Font Format",
     "Windows Embedded CE binary image",
-    "Intel serial flash for PCH ROM",
+    "Xilinx BIT data",
+    "compiled Java class",
+    "magic binary file",
+    "python",  #   # (e.g. python 2.7 byte-compiled)
 )
 DEFAULT_SKIP_EXTENSION = (".rlib",)