Fix bug in QPY symengine payload version handling

This commit fixes a bug that slipped into the sole fix that made up
the now yanked 1.2.3 release, Qiskit#13251. The fix logic had a typo/mistake
when evaluating the major version in the symengine payload that meant
if you were trying to load a QPY payload generated with a different
symengine release it would always error. This only got through CI because
there was no test coverage of the edge case we were trying to fix. This
commit addresses both issues. It first fixes the typo in the QPY parsing
(which is a 2 character change) and then updates the QPY compat tests to
explicitly test using multiple symengine versions with QPY to make sure
we're exercising this code path moving forward (and validating this
fix).

qiskit/qpy/__init__.py

@@ -118,11 +118,11 @@
 
 .. note::
 
-    With versions of Qiskit before 1.2.3, the ``use_symengine=True`` argument to :func:`.qpy.dump`
+    With versions of Qiskit before 1.2.4, the ``use_symengine=True`` argument to :func:`.qpy.dump`
     could cause problems with backwards compatibility if there were :class:`.ParameterExpression`
     objects to serialize.  In particular:
 
-    * When the loading version of Qiskit is 1.2.3 or greater, QPY files generated with any version
+    * When the loading version of Qiskit is 1.2.4 or greater, QPY files generated with any version
       of Qiskit >= 0.46.0 can be loaded.  If a version of Qiskit between 0.45.0 and 0.45.3 was used
       to generate the files, and the non-default argument ``use_symengine=True`` was given to
       :func:`.qpy.dump`, the file can only be read if the version of ``symengine`` used in the
@@ -134,7 +134,7 @@
       used in the generating environment.
 
     To recover a QPY file that fails with ``symengine`` version-related errors during a call to
-    :func:`.qpy.load`, first attempt to use Qiskit >= 1.2.3 to load the file.  If this still fails,
+    :func:`.qpy.load`, first attempt to use Qiskit >= 1.2.4 to load the file.  If this still fails,
     it is likely because Qiskit 0.45.x was used to generate the file with ``use_symengine=True``.
     In this case, use Qiskit 0.45.3 with ``symengine==0.9.2`` to load the file, and then re-export
     it to QPY setting ``use_symengine=False``.  The resulting file can then be loaded by any later

qiskit/qpy/common.py

@@ -322,7 +322,7 @@ def load_symengine_payload(payload: bytes) -> symengine.Expr:
     major = payload[2]
     minor = payload[3]
     if int(symengine_version[1]) != minor:
-        if major != "0":
+        if major != 0:
             raise exceptions.QpyError(
                 "Qiskit doesn't support loading a symengine payload generated with symengine >= 1.0"
             )

qiskit/qpy/interface.py

@@ -149,7 +149,7 @@ def dump(
                 If serializing a :class:`.QuantumCircuit` or :class:`.ScheduleBlock` that contain
                 :class:`.ParameterExpression` objects with ``version`` set low with the intent to
                 load the payload using a historical release of Qiskit, it is safest to set the
-                ``use_symengine`` flag to ``False``.  Versions of Qiskit prior to 1.2.3 cannot load
+                ``use_symengine`` flag to ``False``.  Versions of Qiskit prior to 1.2.4 cannot load
                 QPY files containing ``symengine``-serialized :class:`.ParameterExpression` objects
                 unless the version of ``symengine`` used between the loading and generating
                 environments matches.

releasenotes/notes/fix-qpy-parsing-123-75357c3709e35963.yaml

@@ -0,0 +1,10 @@
+---
+fixes:
+  - |
+    Fixed an issue introduced in the now
+    `yanked <https://peps.python.org/pep-0592/>`__ 1.2.3 bugfix release that
+    would cause an exception with the error message "Qiskit doesn't support
+    loading a symengine payload generated with symengine >= 1.0" to be raised
+    whenever loading a QPY file that was generated with a different symengine
+    version from the version installed by the loading. This issue could only
+    occur in 1.2.3.

releasenotes/notes/fix-qpy-symengine-compat-858970a9a1d6bc14.yaml

@@ -15,7 +15,7 @@ fixes:
     work.
 issues:
   - |
-    Versions of Qiskit before 1.2.3 will not be able to load QPY files dumped
+    Versions of Qiskit before 1.2.4 will not be able to load QPY files dumped
     using :func:`.qpy.dump`, even with ``version`` set appropriately, if:
 
     * there are unbound :class:`.ParameterExpression`\ s in the QPY file,
@@ -25,15 +25,15 @@ issues:
       environments are not within the same minor version.
 
     This applies regardless of the version of Qiskit used in the generation (at
-    least up to Qiskit 1.2.3 inclusive).
+    least up to Qiskit 1.2.4 inclusive).
 
     If you want to maximize compatibility with older versions of Qiskit, you
     should set ``use_symengine=False``.  Newer versions of Qiskit should not
     require this.
   - |
     QPY files from the Qiskit 0.45 series can, under a very specific and unlikely
     set of circumstances, fail to load with any newer version of Qiskit,
-    including Qiskit 1.2.3.  The criteria are:
+    including Qiskit 1.2.4.  The criteria are:
 
     * the :class:`.QuantumCircuit` or :class:`.ScheduleBlock` to be dumped
       contained unbound :class:`.ParameterExpression` objects,

test/qpy_compat/get_versions.py

@@ -70,7 +70,7 @@ def available_versions_for_package(package, min_version=None, max_version=None):
             if not any(
                 tag in supported_tags
                 for release in payload
-                if release["packagetype"] == "bdist_wheel"
+                if release["packagetype"] == "bdist_wheel" and not release["yanked"]
                 for tag in tags_from_wheel_name(release["filename"])
             ):
                 print(

test/qpy_compat/run_tests.sh

@@ -26,11 +26,30 @@ qiskit_venv="$(pwd -P)/qiskit_venv"
 qiskit_python="$qiskit_venv/bin/python"
 python -m venv "$qiskit_venv"
 # `packaging` is needed for the `get_versions.py` script.
-"$qiskit_venv/bin/pip" install -c "$our_dir/../../constraints.txt" "$our_dir/../.." packaging
+#  symengine is pinned to 0.13 to explicitly test the migration path reusing the venv
+"$qiskit_venv/bin/pip" install -c "$our_dir/../../constraints.txt" "$our_dir/../.." packaging "symengine~=0.13"
 
 "$qiskit_python" "$our_dir/get_versions.py" | parallel --colsep=" " bash "$our_dir/process_version.sh" -p "$qiskit_python"
 
 # Test dev compatibility
 dev_version="$("$qiskit_python" -c 'import qiskit; print(qiskit.__version__)')"
 "$qiskit_python" "$our_dir/test_qpy.py" generate --version="$dev_version"
 "$qiskit_python" "$our_dir/test_qpy.py" load --version="$dev_version"
+
+# Test dev compatibility with different symengine versions across 0.11 and 0.13
+#
+# NOTE: When symengine >= 0.14.0 is released we will need to modify this to build an explicit
+# symengine 0.13.0 venv instead of reusing $qiskit_venv.
+#
+symengine_11_venv="$(pwd -P)/qiskit_symengine_11_venv"
+symengine_11_python="$symengine_11_venv/bin/python"
+python -m venv "$symengine_11_venv"
+"$symengine_11_venv/bin/pip" install -c "$our_dir/../../constraints.txt" "$our_dir/../.." "symengine==0.11.0"
+# Load symengine 0.13.0 generated payload with symengine 0.11
+"$symengine_11_python" "$our_dir/test_qpy.py" load --version="$dev_version"
+# Load symengine 0.11.0 generated payload with symengine 0.13.0
+mkdir symengine_11_qpy_files
+pushd symengine_11_qpy_files
+"$symengine_11_python" "$our_dir/test_qpy.py" generate --version="$dev_version"
+"$qiskit_python" "$our_dir/test_qpy.py" load --version="$dev_version"
+popd