zxing-cpp: add build-zxing-cpp.yml for riscv64 wheels (#1653)

* **Package**: `zxing-cpp`
* **Version**: `3.1.1`
* **Source**: https://github.com/zxing-cpp/zxing-cpp
* **Docs**: https://github.com/zxing-cpp/zxing-cpp

Compiles the ZXing-C++ barcode/QR-code reading and writing library into a nanobind Python extension. Upstream publishes no riscv64 wheel.

Mirrors [upstream's `publish-python.yml`](https://github.com/zxing-cpp/zxing-cpp/blob/v3.1.1/.github/workflows/publish-python.yml), building `wrappers/python` straight from the checkout.

**Differs from upstream**
- Drops cp310/cp311 and musllinux - matches this repo's cp312 floor and upstream's own `skip` list.

**Matrix**: cp312 (abi3, also covers cp313/cp314) and cp314t only - the nanobind module is built `STABLE_ABI FREE_THREADED`, so one non-free-threaded build satisfies every interpreter.

**Testing**
- same as upstream

**License**: OK

Built on cp312; pending CI results.

Author: luhenry

.github/workflows/build-zxing-cpp.yml

@@ -0,0 +1,90 @@
+# SPDX-FileCopyrightText: 2026 The RISE Project
+# SPDX-License-Identifier: MIT
+---
+# This workflow is based on upstream's own wheel build setup:
+#   https://github.com/zxing-cpp/zxing-cpp/blob/v3.1.1/.github/workflows/publish-python.yml
+#   https://github.com/zxing-cpp/zxing-cpp/blob/v3.1.1/wrappers/python/pyproject.toml
+name: Build zxing-cpp wheels (riscv64)
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'zxing-cpp version/tag to build (git tag without leading v, e.g. 3.1.1)'
+        required: true
+        default: '3.1.1'
+  pull_request:
+    paths:
+      - '.github/workflows/build-zxing-cpp.yml'
+      - 'patches/zxing-cpp/**'
+
+concurrency:
+  group: ${{ github.workflow }}-${{ inputs.version || '3.1.1' }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read  # to fetch code (actions/checkout)
+
+env:
+  ZXING_CPP_VERSION: ${{ inputs.version || '3.1.1' }}
+  MANYLINUX_RISCV64_IMAGE: quay.io/pypa/manylinux_2_39_riscv64
+
+jobs:
+  setup:
+    uses: $/.github/workflows/_setup.yml
+
+  build_wheels:
+    needs: [setup]
+    name: Build zxing-cpp ${{ inputs.version || '3.1.1' }} ${{ matrix.build }}
+    runs-on: ubuntu-24.04-riscv
+    strategy:
+      fail-fast: false
+      matrix:
+        # wrappers/python/pyproject.toml builds a STABLE_ABI nanobind module tagged
+        # cp312-abi3, so one cp312 build covers cp312/cp313/cp314; only the
+        # FREE_THREADED cp314t build needs its own wheel (upstream's own build list is
+        # cp310-cp312 + cp313t/cp314t, collapsed the same way per gotcha 11).
+        build:
+          - "cp312-manylinux_riscv64"
+          - "cp314t-manylinux_riscv64"
+
+    steps:
+      - name: Checkout zxing-cpp v${{ env.ZXING_CPP_VERSION }}
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          repository: zxing-cpp/zxing-cpp
+          ref: v${{ env.ZXING_CPP_VERSION }}
+          submodules: true
+          persist-credentials: false
+
+      - name: Checkout python-wheels
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
+        with:
+          path: python-wheels
+          persist-credentials: false
+
+      - name: Apply patches
+        run: git apply python-wheels/patches/zxing-cpp/${{ env.ZXING_CPP_VERSION }}/*.patch
+
+      - uses: pypa/cibuildwheel@1828c10ab37f080699c7b81cea34097c684a7074  # v4.2.0
+        with:
+          package-dir: wrappers/python
+          only: ${{ matrix.build }}
+        env:
+          CIBW_MANYLINUX_RISCV64_IMAGE: ${{ env.MANYLINUX_RISCV64_IMAGE }}
+
+      - uses: actions/upload-artifact@043fb46d1a93c77aae656e7c1c64a875d1fc6a0a  # v7.0.1
+        with:
+          name: zxing-cpp-${{ env.ZXING_CPP_VERSION }}-${{ matrix.build }}
+          path: ./wheelhouse/*.whl
+          if-no-files-found: error
+
+  publish:
+    name: Publish zxing-cpp ${{ inputs.version || '3.1.1' }}
+    needs: [setup, build_wheels]
+    permissions:
+      contents: write
+      pull-requests: write
+    uses: $/.github/workflows/_publish-wheel.yml
+    with:
+      artifact-pattern: zxing-cpp-${{ inputs.version || '3.1.1' }}-*-manylinux_riscv64

patches/zxing-cpp/3.1.1/0001-python-drop-the-cpython-freethreading-cibuildwheel-.patch

@@ -0,0 +1,37 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Ludovic Henry <git@ludovic.dev>
+Date: Wed, 10 Sep 2026 00:00:00 +0000
+Subject: [PATCH] python: drop the cpython-freethreading cibuildwheel enable
+ group
+
+Upstream-Status: Inappropriate [pinned to an older cibuildwheel release for this repo's other ports]
+
+wrappers/python/pyproject.toml's [tool.cibuildwheel] table sets
+`enable = ["cpython-freethreading"]`, a group name introduced in a
+cibuildwheel release newer than the one this repo pins
+(pypa/cibuildwheel@1828c10, v4.2.0). That version's config parser
+rejects it outright: "Failed to parse enable group. Unknown enable
+group: cpython-freethreading. Valid group names are:
+cpython-prerelease, graalpy, pypy, pypy-eol, pyodide-eol,
+pyodide-prerelease" -- this aborts before build selection even runs,
+so setting `CIBW_ENABLE=""` in the workflow env does not help, since
+an empty override doesn't override, it turns off.
+
+The cp314t leg is already selected explicitly via this repo's own
+`only:` matrix entry in build-zxing-cpp.yml, so the enable group is
+redundant for our build regardless of cibuildwheel version.
+
+diff --git a/wrappers/python/pyproject.toml b/wrappers/python/pyproject.toml
+index 0000000..0000000 100644
+--- a/wrappers/python/pyproject.toml
++++ b/wrappers/python/pyproject.toml
+@@ -54,7 +54,6 @@
+ # note: stable ABI and free-threaded builds are mutually exclusive,
+ # see https://nanobind.readthedocs.io/en/latest/free_threaded.html
+ build = ["cp310-*", "cp311-*", "cp312-*", "cp313t-*", "cp314t-*"]
+-enable = ["cpython-freethreading"]
+ skip = ["*musllinux*", "*-win32"]
+ # TODO: setup a "BEFORE" cmake build and link the python module to the prebuild libZXing.a
+ # see https://github.com/YannickJadoul/Parselmouth/blob/523c117aa780184345121f6ff8315670bc7d4d94/.github/workflows/wheels.yml#L120
+--
+2.43.0