Make IsalError exceptions picklable

CHANGELOG.rst

@@ -7,6 +7,14 @@ Changelog
 .. This document is user facing. Please word the changes in such a way
 .. that users understand how the changes affect the new version.
 
+version 1.10.0-dev
+------------------
++ Fix pickling of ``isal_zlib.error`` (``igzip_lib.IsalError``). An error
+  raised in a ``multiprocessing`` worker process did not reach the parent
+  process. Tracebacks now show ``isal.igzip_lib.IsalError`` instead of
+  ``igzip_lib.IsalError``.
+
+
 version 1.9.1
 -----------------
 + Fix BrokenPipeError when piping ``python -m isal.igzip`` into ``head``,

src/isal/igzip_libmodule.c

@@ -696,7 +696,8 @@ PyInit_igzip_lib(void)
 #endif
 
 
-    IsalError = PyErr_NewException("igzip_lib.IsalError", NULL, NULL);
+    /* The full module name lets pickle find the class. */
+    IsalError = PyErr_NewException("isal.igzip_lib.IsalError", NULL, NULL);
     if (IsalError == NULL) {
         return NULL;
     }

tests/test_igzip_lib.py

@@ -19,7 +19,7 @@
 import zlib
 from typing import NamedTuple
 
-from isal import igzip_lib
+from isal import igzip_lib, isal_zlib
 from isal.igzip_lib import (
     COMP_DEFLATE, COMP_GZIP, COMP_GZIP_NO_HDR, COMP_ZLIB, COMP_ZLIB_NO_HDR,
     DECOMP_DEFLATE, DECOMP_GZIP, DECOMP_GZIP_NO_HDR, DECOMP_GZIP_NO_HDR_VER,
@@ -239,6 +239,17 @@ def test_failure(self):
         with pytest.raises(igzip_lib.IsalError):
             igzd.decompress(self.BAD_DATA * 30)
 
+    @pytest.mark.parametrize("module", [igzip_lib, isal_zlib])
+    def test_failure_pickle(self, module):
+        # multiprocessing pickles an error raised in a worker process to send
+        # it to the parent process.
+        with pytest.raises(igzip_lib.IsalError) as raised:
+            module.decompress(self.BAD_DATA)
+        for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+            error = pickle.loads(pickle.dumps(raised.value, proto))
+            assert type(error) is igzip_lib.IsalError
+            assert error.args == raised.value.args
+
     def test_dictionary(self):
         compressor = zlib.compressobj(zdict=b"bla")
         data = compressor.compress(b"bladiebla") + compressor.flush()