Don't test forward compatibility in qpy compat tests (backport #11101)

test/qpy_compat/compare_versions.py

@@ -0,0 +1,40 @@
+#!/usr/bin/env python3
+# This code is part of Qiskit.
+#
+# (C) Copyright IBM 2023.
+#
+# This code is licensed under the Apache License, Version 2.0. You may
+# obtain a copy of this license in the LICENSE.txt file in the root directory
+# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
+#
+# Any modifications or derivative works of this code must retain this
+# copyright notice, and modified files need to carry a notice indicating
+# that they have been altered from the originals.
+
+"""Compare Qiskit versions to determine if we should run qpy compat tests."""
+
+import argparse
+import sys
+
+from qiskit.qpy.interface import VERSION_PATTERN_REGEX
+
+
+def main():
+    """Main function."""
+    parser = argparse.ArgumentParser(prog="compare_version", description="Compare version strings")
+    parser.add_argument(
+        "source_version", help="Source version of Qiskit that is generating the payload"
+    )
+    parser.add_argument("test_version", help="Version under test that will load the QPY payload")
+    args = parser.parse_args()
+    source_match = VERSION_PATTERN_REGEX.search(args.source_version)
+    target_match = VERSION_PATTERN_REGEX.search(args.test_version)
+    source_version = tuple(int(x) for x in source_match.group("release").split("."))
+    target_version = tuple(int(x) for x in target_match.group("release").split("."))
+    if source_version > target_version:
+        sys.exit(1)
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()

test/qpy_compat/process_version.sh

@@ -14,9 +14,25 @@
 set -e
 set -x
 
+# version is the source version, this is the release with which to generate
+# qpy files with to load with the version under test
 version=$1
 parts=( ${version//./ } )
-if [[ ${parts[1]} -lt 18 ]] ; then
+# qiskit_version is the version under test, We're testing that we can correctly
+# read the qpy files generated with source version with this version.
+qiskit_version=`./qiskit_venv/bin/python -c "import qiskit;print(qiskit.__version__)"`
+qiskit_parts=( ${qiskit_version//./ } )
+
+
+# If source version is less than 0.18 QPY didn't exist yet so exit fast
+if [[ ${parts[0]} -eq 0 && ${parts[1]} -lt 18 ]] ; then
+    exit 0
+fi
+
+# If the source version is newer than the version under test exit fast because
+# there is no QPY compatibility for loading a qpy file generated from a newer
+# release with an older release of Qiskit.
+if ! ./qiskit_venv/bin/python ./compare_versions.py "$version" "$qiskit_version" ; then
     exit 0
 fi