From 74274ec8bccc47c80f7302e3ce14e430826fe1ac Mon Sep 17 00:00:00 2001
From: Alistair Coles <alistairncoles@gmail.com>
Date: Thu, 14 Aug 2025 11:14:41 +0100
Subject: [PATCH] checksum.py: fail gracefully if pyeclib is broken

If pyeclib dist is missing files then the isal loading would blow up
with "TypeError: 'NoneType' object is not iterable". This patch
changes that to a RuntimeError with a more useful message.

Change-Id: I64a85eb739fb72efe41f1ee829e463167246b793
Closes-Bug: #2120591
Signed-off-by: Alistair Coles <alistairncoles@gmail.com>
---
 swift/common/utils/checksum.py          | 39 +++++++++++++++----------
 test/unit/common/utils/test_checksum.py | 14 +++++++++
 2 files changed, 37 insertions(+), 16 deletions(-)

diff --git a/swift/common/utils/checksum.py b/swift/common/utils/checksum.py
index d62b284a57..9f9a273ebc 100644
--- a/swift/common/utils/checksum.py
+++ b/swift/common/utils/checksum.py
@@ -25,12 +25,6 @@ import socket
 import struct
 import zlib
 
-try:
-    import pyeclib  # noqa
-    from importlib.metadata import files as pkg_files  # py38+
-except ImportError:
-    pkg_files = None
-
 
 # See if anycrc is available...
 if anycrc:
@@ -41,17 +35,30 @@ else:
     crc64nvme_anycrc = None
 
 
-# If isal is available system-wide, great!
-isal_lib = ctypes.util.find_library('isal')
-if isal_lib is None and pkg_files is not None:
-    # py38+: Hopefully pyeclib was installed from a manylinux wheel
-    # with isal baked in?
-    isal_libs = [f for f in pkg_files('pyeclib')
-                 if f.name.startswith("libisal")]
-    if len(isal_libs) == 1:
-        isal_lib = isal_libs[0].locate()
+def find_isal():
+    # If isal is available system-wide, great!
+    isal_lib = ctypes.util.find_library('isal')
+    if isal_lib is None:
+        # py38+: Hopefully pyeclib was installed from a manylinux wheel
+        # with isal baked in?
+        try:
+            import pyeclib  # noqa
+            from importlib.metadata import files as pkg_files  # py38+
+        except ImportError:
+            pass
+        else:
+            pyeclib_files = pkg_files('pyeclib')
+            if not pyeclib_files:
+                # see https://docs.python.org/3/library/importlib.metadata.html
+                raise RuntimeError('pyeclib installed but missing files')
+            isal_libs = [f for f in pyeclib_files
+                         if f.name.startswith("libisal")]
+            if len(isal_libs) == 1:
+                isal_lib = isal_libs[0].locate()
+    return ctypes.CDLL(isal_lib) if isal_lib else None
 
-isal = ctypes.CDLL(isal_lib) if isal_lib else None
+
+isal = find_isal()
 
 if hasattr(isal, 'crc32_iscsi'):  # isa-l >= 2.16
     isal.crc32_iscsi.argtypes = [ctypes.c_char_p, ctypes.c_int, ctypes.c_uint]
diff --git a/test/unit/common/utils/test_checksum.py b/test/unit/common/utils/test_checksum.py
index 144f90bba5..87ffe29bac 100644
--- a/test/unit/common/utils/test_checksum.py
+++ b/test/unit/common/utils/test_checksum.py
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import sys
 import unittest
 from unittest import mock
 
@@ -23,6 +24,19 @@ from test.debug_logger import debug_logger
 from test.unit import requires_crc32c, requires_crc64nvme
 
 
+class TestModuleFunctions(unittest.TestCase):
+    @unittest.skipIf(
+        sys.version_info.major == 3 and sys.version_info.minor < 8,
+        "importlib.metadata not available until py3.8")
+    def test_find_isal_pyeclib_dist_missing_files(self):
+        with mock.patch('ctypes.util.find_library', return_value=None):
+            with mock.patch('importlib.metadata.files', return_value=None):
+                with self.assertRaises(RuntimeError) as cm:
+                    checksum.find_isal()
+        self.assertEqual('pyeclib installed but missing files',
+                         str(cm.exception))
+
+
 # If you're curious about the 0xe3069283, see "check" at
 # https://reveng.sourceforge.io/crc-catalogue/17plus.htm#crc.cat.crc-32-iscsi
 class TestCRC32C(unittest.TestCase):