Add tests to reproduce bug where openening with a wrong compresslevel in read mode causes a crash.

Author: rhpvorderman

tests/test_gzip_compliance.py

@@ -456,6 +456,13 @@ def test_with_open(self):
         else:
             self.fail("1/0 didn't raise an exception")
 
+    def test_read_and_compresslevel(self):
+        with igzip.GzipFile(self.filename, "wb") as f:
+            f.write(b"xxx")
+        with igzip.GzipFile(self.filename, "rb", compresslevel=17) as f:
+            data = f.read()
+        assert data == b"xxx"
+
     def test_zero_padded_file(self):
         with igzip.GzipFile(self.filename, "wb") as f:
             f.write(data1 * 50)
@@ -785,6 +792,13 @@ def test_newline(self):
         with igzip.open(self.filename, "rt", newline="\r") as f:
             self.assertEqual(f.readlines(), [uncompressed])
 
+    def test_reading_and_compresslevel(self):
+        with igzip.open(self.filename, "wb") as f:
+            f.write(data1)
+        with igzip.open(self.filename, "rb", compresslevel=17) as f:
+            text = f.read()
+        assert text == data1
+
 
 def create_and_remove_directory(directory):
     def decorator(function):

tests/test_igzip_threaded.py

@@ -191,3 +191,11 @@ def test_igzip_threaded_append_text_mode(tmp_path):
     with gzip.open(test_file, "rt") as f:
         contents = f.read()
     assert contents == "ABCD"
+
+
+def test_igzip_threaded_open_compresslevel_and_reading(tmp_path):
+    test_file = tmp_path / "test.txt.gz"
+    test_file.write_bytes(gzip.compress(b"thisisatest"))
+    with igzip_threaded.open(test_file, compresslevel=5) as f:
+        text = f.read()
+    assert text == b"thisisatest"