Fix 'python -m snappy -d' (cannot unpack non-iterable function object)

.github/workflows/wheel.yml

@@ -38,7 +38,7 @@ jobs:
         run: pip install dist/python-snappy*.tar.gz
 
       - name: Pytest
-        run: pytest --verbose test_snappy.py
+        run: pytest --verbose test_snappy.py test_formats.py
 
       - name: Archive sdist
         uses: actions/upload-artifact@v4

src/snappy/__main__.py

@@ -71,20 +71,21 @@ def cmdline_main():
     if isinstance(args.outfile, io.TextIOWrapper):
         args.outfile = stdout
 
-    additional_args = {}
     if args.compress:
         method = formats.get_compress_function(args.target_format)
     else:
         try:
-            method, read_chunk = formats.get_decompress_function(
+            method = formats.get_decompress_function(
                 args.target_format,
                 args.infile
             )
         except UncompressError as err:
             sys.exit("Failed to get decompress function: {}".format(err))
-        additional_args['start_chunk'] = read_chunk
+        if args.target_format == "auto":
+            # guessing the format reads from the input, so rewind it
+            args.infile.seek(0)
 
-    method(args.infile, args.outfile, **additional_args)
+    method(args.infile, args.outfile)
 
 
 if __name__ == "__main__":

test_formats.py

@@ -1,5 +1,8 @@
 import io
 import os
+import subprocess
+import sys
+import tempfile
 from unittest import TestCase
 
 from snappy import snappy_formats as formats
@@ -72,6 +75,30 @@ class TestFormatRawAuto(TestFormatBase):
     success = True
 
 
+class TestCommandLine(TestCase):
+    def test_compress_decompress_roundtrip(self):
+        data = os.urandom(1024 * 256 * 2) + os.urandom(13245 * 2)
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            plain = os.path.join(tmp_dir, "plain")
+            compressed = os.path.join(tmp_dir, "compressed.snappy")
+            with open(plain, "wb") as f:
+                f.write(data)
+            subprocess.run(
+                [sys.executable, "-m", "snappy", "-c", plain, compressed],
+                check=True,
+            )
+            for target_format in formats.ALL_SUPPORTED_FORMATS:
+                with self.subTest(target_format=target_format):
+                    decompressed = os.path.join(tmp_dir, target_format)
+                    subprocess.run(
+                        [sys.executable, "-m", "snappy", "-d",
+                         "-t", target_format, compressed, decompressed],
+                        check=True,
+                    )
+                    with open(decompressed, "rb") as f:
+                        self.assertEqual(data, f.read())
+
+
 if __name__ == "__main__":
     import unittest
     unittest.main()