From b84ce7188c60e35cdfcb18426f23aad647b1d86d Mon Sep 17 00:00:00 2001
From: Jim Garrison <garrison@ibm.com>
Date: Wed, 7 Oct 2026 17:06:00 -0400
Subject: [PATCH] Test the minimum supported dependency versions

The Tests workflow installs the newest version of everything, so the
floors declared in pyproject.toml were never exercised.  Add a workflow
that pins every dependency to its declared minimum with
extremal-python-dependencies and runs the suite, following the pattern
used in qiskit-addon-sqd.

Standing the workflow up showed the existing floors were aspirational
rather than tested, and none of them installed:

- mpi4py 3.0.0 does not build against current setuptools, whose
  new_compiler() no longer accepts the dry_run argument mpi4py's build
  scripts pass.  Every 3.x release fails this way, so the floor becomes
  4.0.0.
- pybind11 2.6.0's headers do not compile with a current GCC: attr.h and
  pybind11.h use std::uint16_t without including <cstdint>.  2.12.0 is
  the oldest that builds here.
- numpy 1.19.0 predates Python 3.10 and has no wheel for any supported
  version, so it built from source and failed.  It was also inconsistent
  with the test extra, since qiskit-addon-sqd requires numpy>=1.26.
- setuptools>=77 pins to the exact version "77", which does not exist on
  PyPI; the first 77.x release is 77.0.1.

With those raised, `pip install .[test]` resolves in a single pass and
the serial and MPI suites both pass on Python 3.10.  Note that pinning
numpy to 1.26.0 backtracks qiskit to 2.4.2, since qiskit 2.5 requires
numpy>=2.0 -- that is the resolver doing its job, not a conflict.

Only Linux and Python 3.10 are covered, matching the original: the floors
are what is under test here, not the platform matrix.

Development-version tests were first suggested in #6 alongside these,
which stays open for the remaining items.

Assisted-by: Claude Opus 5
---
 .github/workflows/test_minimum_versions.yml   | 49 +++++++++++++++++++
 pyproject.toml                                |  8 +--
 ...pported-dependencies-b1e7c5649c3201d1.yaml |  8 +++
 3 files changed, 61 insertions(+), 4 deletions(-)
 create mode 100644 .github/workflows/test_minimum_versions.yml
 create mode 100644 releasenotes/notes/minimum-supported-dependencies-b1e7c5649c3201d1.yaml

diff --git a/.github/workflows/test_minimum_versions.yml b/.github/workflows/test_minimum_versions.yml
new file mode 100644
index 0000000..1e775fe
--- /dev/null
+++ b/.github/workflows/test_minimum_versions.yml
@@ -0,0 +1,49 @@
+name: Minimum version tests
+
+on:
+  push:
+    branches:
+      - main
+      - 'stable/**'
+  pull_request:
+    branches:
+      - main
+      - 'stable/**'
+
+jobs:
+  tests:
+    name: minimum version tests (${{ matrix.os }}, ${{ matrix.python-version }})
+    runs-on: ${{ matrix.os }}
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      max-parallel: 4
+      matrix:
+        os: [ubuntu-latest]
+        python-version: ["3.10"]
+    steps:
+      - uses: actions/checkout@v7
+        with:
+          # The reference energies the tests check against come from data in the
+          # vendored upstream checkout, and setup.py needs its headers to compile.
+          submodules: recursive
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v7
+        with:
+          python-version: ${{ matrix.python-version }}
+      - name: Install MPI and BLAS (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libopenmpi-dev openmpi-bin libopenblas-dev
+      - name: Install dependencies (minimum versions)
+        shell: bash
+        run: |
+          python -m pip install --upgrade pip
+          python -m pip install 'extremal-python-dependencies<2'
+          pip install "tox==$(extremal-python-dependencies get-tox-minversion)"
+          extremal-python-dependencies pin-dependencies-to-minimum --inplace
+      - name: Test using tox environments
+        shell: bash
+        run: |
+          tox -e py,notebook,mpi
diff --git a/pyproject.toml b/pyproject.toml
index a235da2..30b4ed8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -1,5 +1,5 @@
 [build-system]
-requires = ["setuptools>=77", "wheel", "pybind11>=2.6.0", "mpi4py>=3.0.0"]
+requires = ["setuptools>=77.0.1", "wheel", "pybind11>=2.12.0", "mpi4py>=4.0.0"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -27,8 +27,8 @@ classifiers = [
     "Programming Language :: C++",
 ]
 dependencies = [
-    "mpi4py>=3.0.0",
-    "numpy>=1.19.0",
+    "mpi4py>=4.0.0",
+    "numpy>=1.26.0",
 ]
 
 [project.optional-dependencies]
@@ -83,4 +83,4 @@ testpaths = ["test"]
 # skips by default: a bare count of skips would not distinguish "this case is slow" or
 # "this backend was not built" from "the reference data is missing". --durations shows
 # where the time goes, the cases differing by orders of magnitude in cost.
-addopts = "-rs --durations=10"
\ No newline at end of file
+addopts = "-rs --durations=10"
diff --git a/releasenotes/notes/minimum-supported-dependencies-b1e7c5649c3201d1.yaml b/releasenotes/notes/minimum-supported-dependencies-b1e7c5649c3201d1.yaml
new file mode 100644
index 0000000..e6c7250
--- /dev/null
+++ b/releasenotes/notes/minimum-supported-dependencies-b1e7c5649c3201d1.yaml
@@ -0,0 +1,8 @@
+---
+upgrade:
+  - |
+    The declared minimum versions of several dependencies have been raised to
+    the oldest ones this package actually builds and runs against:
+    ``numpy>=1.26.0`` (was 1.19.0), ``mpi4py>=4.0.0`` (was 3.0.0),
+    ``pybind11>=2.12.0`` (was 2.6.0), and ``setuptools>=77.0.1`` (was 77).
+    The previous floors were aspirational rather than tested.