Add wasm side-module build for wp_mysql_parser and CI to gate it

Spike confirms the Rust extension can be compiled to a PHP-wasm side module
via @php-wasm/compile-extension and loaded into Playground. Build recipe and
findings live in wasm-spike/RESULT.md; the new GitHub Actions workflow runs
the build against wordpress-playground trunk on every PR that touches the
extension and verifies the produced .so loads and parses a query.

The workflow currently fails on a Playground-side blocker (zend_ce_traversable
not exported from PHP-wasm's MAIN_MODULE=2 export set). RESULT.md documents
the blocker and the proposed fix in WordPress/wordpress-playground.

Author: adamziel

.github/workflows/wasm-spike.yml

@@ -0,0 +1,110 @@
+name: WASM extension build
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'packages/php-ext-wp-mysql-parser/**'
+      - '.github/workflows/wasm-spike.yml'
+  pull_request:
+    paths:
+      - 'packages/php-ext-wp-mysql-parser/**'
+      - '.github/workflows/wasm-spike.yml'
+  workflow_dispatch:
+    inputs:
+      playground-ref:
+        description: 'wordpress-playground branch/tag/SHA to build against'
+        required: false
+        default: 'trunk'
+
+jobs:
+  build-and-load:
+    name: Build wp_mysql_parser.so and load it in Playground (PHP ${{ matrix.php }})
+    runs-on: ubuntu-latest
+    timeout-minutes: 45
+    strategy:
+      fail-fast: false
+      matrix:
+        php: ['8.4']
+        async-mode: ['jspi']
+
+    steps:
+      - name: Check out sqlite-database-integration
+        uses: actions/checkout@v4
+        with:
+          path: sqlite-database-integration
+
+      - name: Check out wordpress-playground
+        uses: actions/checkout@v4
+        with:
+          repository: WordPress/wordpress-playground
+          ref: ${{ github.event.inputs.playground-ref || 'trunk' }}
+          path: wordpress-playground
+
+      - name: Set up Node
+        uses: actions/setup-node@v4
+        with:
+          node-version: '22'
+          cache: 'npm'
+          cache-dependency-path: wordpress-playground/package-lock.json
+
+      - name: Install Playground deps
+        working-directory: wordpress-playground
+        run: npm ci
+
+      - name: Build @php-wasm/compile-extension base image
+        working-directory: wordpress-playground
+        run: |
+          npx @php-wasm/compile-extension --help >/dev/null 2>&1 || true
+          docker images | grep playground-php-wasm || true
+
+      - name: Build wp_mysql_parser side module
+        working-directory: sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike
+        env:
+          PHP_VERSION: ${{ matrix.php }}
+          ASYNC_MODE: ${{ matrix.async-mode }}
+        run: bash build-in-docker-rust.sh
+
+      - name: Verify build artifacts exist
+        working-directory: sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike
+        run: |
+          test -f dist/wp_mysql_parser-php${{ matrix.php }}-${{ matrix.async-mode }}.so
+          test -f dist/manifest.json
+          test -f dist/libwp_mysql_parser.a
+          ls -lh dist/
+
+      - name: Verify manifest sha256 matches the .so byte-for-byte
+        working-directory: sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike
+        run: |
+          MANIFEST_SHA=$(node -e "console.log(require('./dist/manifest.json').extensions[0].artifacts[0].sha256)")
+          ACTUAL_SHA=$(sha256sum dist/wp_mysql_parser-php${{ matrix.php }}-${{ matrix.async-mode }}.so | cut -d' ' -f1)
+          echo "manifest: $MANIFEST_SHA"
+          echo "actual:   $ACTUAL_SHA"
+          test "$MANIFEST_SHA" = "$ACTUAL_SHA"
+
+      - name: Load the extension in Playground and parse a query
+        working-directory: sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike
+        env:
+          PLAYGROUND_REPO: ${{ github.workspace }}/wordpress-playground
+        run: node run-spike.mjs
+
+      - name: Upload artifacts on success
+        if: success()
+        uses: actions/upload-artifact@v4
+        with:
+          name: wp_mysql_parser-php${{ matrix.php }}-${{ matrix.async-mode }}
+          path: sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike/dist/
+          if-no-files-found: error
+          retention-days: 14
+
+      - name: Upload diagnostic logs on failure
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: wasm-spike-failure-php${{ matrix.php }}-${{ matrix.async-mode }}
+          path: |
+            sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike/dist/
+            sqlite-database-integration/packages/php-ext-wp-mysql-parser/wasm-spike/*.log
+          if-no-files-found: ignore
+          retention-days: 14

packages/php-ext-wp-mysql-parser/wasm-spike/.gitignore

@@ -0,0 +1,2 @@
+dist/
+*.log

packages/php-ext-wp-mysql-parser/wasm-spike/Dockerfile.rust

@@ -0,0 +1,63 @@
+# Layer that adds rustup + the wasm32-unknown-emscripten target on top of
+# Playground's compile-extension image.
+#
+# Base image is the one produced by `@php-wasm/compile-extension`'s
+# Dockerfile.ext, tagged as
+# `playground-php-wasm:compile-extension-php<MAJOR-MINOR>-<ASYNC>`. It
+# already contains emsdk and a wasm-targeted PHP install with headers under
+# /usr/local/include/php and a matching `php-config` on PATH — exactly what
+# ext-php-rs's bindgen step needs to succeed.
+#
+# Build with:
+#   docker build \
+#     --build-arg BASE_IMAGE=playground-php-wasm:compile-extension-php8-4-jspi \
+#     -t playground-php-wasm-ext-rust:8.4-jspi \
+#     -f Dockerfile.rust .
+
+ARG BASE_IMAGE=playground-php-wasm:compile-extension-php8-4-jspi
+
+# Stage providing a host PHP 8.4 CLI binary. ext-php-rs's build.rs shells
+# out to `php` to detect the PHP version (PHP_VERSION_ID drives the cfg
+# flags php80..php85). The wasm-targeted PHP install in /usr/local has no
+# CLI binary (--disable-cli), Ubuntu noble ships only PHP 8.3, and
+# packages.sury.org blocks our datacenter IP, so we steal a CLI from the
+# official php:8.4-cli image.
+FROM php:8.4-cli AS host-php-cli
+
+FROM ${BASE_IMAGE}
+
+COPY --from=host-php-cli /usr/local/bin/php /opt/host-php/bin/php
+COPY --from=host-php-cli /usr/local/lib/php /opt/host-php/lib/php
+COPY --from=host-php-cli /usr/local/etc/php /opt/host-php/etc/php
+COPY --from=host-php-cli /usr/local/include/php /opt/host-php/include/php
+
+ENV RUSTUP_HOME=/root/rustup \
+    CARGO_HOME=/root/cargo \
+    PATH=/root/cargo/bin:/root/rustup/bin:/usr/local/bin:/usr/bin:/bin
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        curl ca-certificates build-essential \
+        libclang-dev clang llvm-dev pkg-config libxml2 libonig5 libsqlite3-0 \
+        libargon2-1 libssl3 zlib1g libreadline8 \
+    && rm -rf /var/lib/apt/lists/* \
+    && ln -sf /opt/host-php/bin/php /usr/local/bin/php-host
+
+# ext-php-rs's build.rs needs a host `php` executable to query include paths
+# from `php-config`. The wasm-targeted PHP install in /usr/local does not ship
+# a CLI binary (--disable-cli). We install Debian's host php-cli purely so the
+# build script's PHP shells out can run; bindgen still uses
+# /usr/local/bin/php-config (from PATH order) for headers — which IS the wasm
+# PHP install. Set PHP_CONFIG explicitly to make this contract obvious.
+ENV PHP_CONFIG=/usr/local/bin/php-config \
+    PHP=/opt/host-php/bin/php
+
+RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+        | sh -s -- -y --default-toolchain stable --profile minimal \
+    && /root/cargo/bin/rustup target add wasm32-unknown-emscripten \
+    && /root/cargo/bin/rustup toolchain install nightly --profile minimal \
+        --component rust-src \
+    && /root/cargo/bin/rustup target add wasm32-unknown-emscripten --toolchain nightly
+
+# Make libclang discoverable for bindgen regardless of LLVM minor version.
+RUN ln -sf "$(dpkg -L libclang-dev | grep -E 'libclang.so$' | head -1)" /usr/lib/libclang.so || true
+ENV LIBCLANG_PATH=/usr/lib/llvm-18/lib