build(bazel): add experimental RNTester macOS build

.bazelignore

@@ -0,0 +1,40 @@
+node_modules
+.git
+.yarn
+packages/react-native/.build
+packages/rn-tester/Pods
+packages/helloworld
+private/helloworld
+packages/assets/node_modules
+packages/babel-plugin-codegen/node_modules
+packages/community-cli-plugin/node_modules
+packages/core-cli-utils/node_modules
+packages/debugger-frontend/node_modules
+packages/debugger-shell/node_modules
+packages/dev-middleware/node_modules
+packages/eslint-config-react-native/node_modules
+packages/eslint-plugin-react-native/node_modules
+packages/eslint-plugin-specs/node_modules
+packages/gradle-plugin/node_modules
+packages/metro-config/node_modules
+packages/new-app-screen/node_modules
+packages/normalize-color/node_modules
+packages/polyfills/node_modules
+packages/react-native-babel-preset/node_modules
+packages/react-native-babel-transformer/node_modules
+packages/react-native-codegen/node_modules
+packages/react-native-compatibility-check/node_modules
+packages/react-native-macos-init/node_modules
+packages/react-native-popup-menu-android/node_modules
+packages/react-native-test-library/node_modules
+packages/react-native/node_modules
+packages/rn-tester/node_modules
+packages/typescript-config/node_modules
+packages/virtualized-lists/node_modules
+private/cxx-public-api/node_modules
+private/eslint-plugin-monorepo/node_modules
+private/monorepo-tests/node_modules
+private/react-native-bots/node_modules
+private/react-native-codegen-typescript-test/node_modules
+private/react-native-fantom/node_modules
+tools/bazel/berry/example/node_modules

.bazelrc

@@ -0,0 +1,24 @@
+# react-native-macos Bazel configuration (draft / experimental)
+# See docs/bazel.md for the design and current status.
+
+# Our pnpm-lock.yaml is generated on the fly from the Berry yarn.lock by the
+# rules_js fork, so we don't pin the module resolution in MODULE.bazel.lock.
+common --lockfile_mode=off
+
+# Local disk cache (also the base for the GHA actions/cache remote cache).
+build --disk_cache=~/.cache/bazel-rnm-disk
+
+# Nicer output.
+build --show_result=1
+
+# Apple: build macOS slices. Scoped in practice to the app target's transitions.
+build:macos --apple_platform_type=macos
+
+# React Native's new architecture C++ (Fabric/TurboModules) requires C++20.
+# Scope the flag to C++/Obj-C++: objc_library also compiles plain `.m` files, and
+# clang rejects `-std=c++20` when it is passed to Objective-C.
+build --per_file_copt=.*\\.(cc|cpp|cxx|mm)$@-std=c++20
+
+# CI convenience config.
+build:ci --color=yes
+build:ci --show_timestamps

.bazelversion

@@ -0,0 +1 @@
+8.7.0

.eslintignore

@@ -14,5 +14,6 @@ packages/*/types_generated
 packages/debugger-frontend/dist/**/*
 packages/react-native-codegen/lib
 **/Pods/*
+bazel-*
 **/*.macos.js
 **/*.windows.js

.github/workflows/bazel.yml

@@ -0,0 +1,103 @@
+# Experimental Bazel CI for react-native-macos.
+#
+# Today this verifies the rules_js *Berry fork* end to end: it builds/tests a target
+# whose node_modules are materialized from a Yarn Berry `yarn.lock` (translated to a
+# pnpm-lock by tools/bazel/berry, with no committed second lockfile). The macOS app
+# slice (rules_apple) is added incrementally — see docs/bazel.md.
+name: Bazel (experimental)
+
+on:
+  pull_request:
+    paths:
+      - "MODULE.bazel"
+      - ".bazelrc"
+      - ".bazelversion"
+      - ".bazelignore"
+      - ".yarnrc.yml"
+      - "BUILD.bazel"
+      - "package.json"
+      - "yarn.lock"
+      - "tools/bazel/**"
+      - "packages/react-native/**"
+      - "packages/rn-tester/**"
+      - ".github/workflows/bazel.yml"
+  workflow_dispatch: {}
+
+permissions:
+  contents: read
+
+concurrency:
+  group: bazel-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  berry-fork:
+    name: rules_js Berry fork (JS)
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+      # Disk cache doubles as a simple GHA-backed Bazel remote cache. For a real
+      # remote cache at scale, point --remote_cache at BuildBuddy or a self-hosted
+      # bazel-remote (see docs/bazel.md).
+      - name: Cache Bazel
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/bazel-rnm-disk
+          key: bazel-berry-${{ runner.os }}-${{ hashFiles('MODULE.bazel', 'yarn.lock', 'tools/bazel/**') }}
+          restore-keys: |
+            bazel-berry-${{ runner.os }}-
+      - name: Verify generated workspace BUILD files
+        run: node tools/bazel/js/gen_package_builds.mjs --all --check
+      - name: Test the Berry -> rules_js pipeline end to end
+        run: |
+          npx --yes @bazel/bazelisk test //tools/bazel/berry/example:verify \
+            --config=ci --test_output=errors
+
+  rntester-macos:
+    name: RNTester macOS from source
+    runs-on: macos-26
+    timeout-minutes: 90
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          filter: blob:none
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+
+      - name: Cache Bazel
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/bazel-rnm-disk
+          key: bazel-rntester-macos-${{ hashFiles('MODULE.bazel', 'yarn.lock', 'packages/react-native/Package.swift', 'tools/bazel/**') }}
+          restore-keys: |
+            bazel-rntester-macos-
+
+      - name: Build RNTester from a clean checkout
+        run: |
+          test ! -e packages/react-native/.build/output/xcframeworks/Debug/React.xcframework
+          test ! -e packages/react-native/third-party/ReactNativeDependencies.xcframework
+          test ! -e packages/react-native/.build/artifacts/hermes/destroot
+          npx --yes @bazel/bazelisk build \
+            //packages/rn-tester/RNTester-macOS:app \
+            --config=ci
+
+      - name: Verify source-linked app
+        run: |
+          mkdir -p "$RUNNER_TEMP/rntester"
+          unzip -q bazel-bin/packages/rn-tester/RNTesterMacBazelFull.zip \
+            -d "$RUNNER_TEMP/rntester"
+          app="$RUNNER_TEMP/rntester/RNTesterMacBazelFull.app"
+          test -f "$app/Contents/Resources/main.jsbundle"
+          test -f "$app/Contents/Resources/Assets.car"
+          test -f "$app/Contents/Resources/PrivacyInfo.xcprivacy"
+          test "$(find "$app/Contents/Resources" -name 'bottom-nav-*.png' | wc -l | tr -d ' ')" = 6
+          test ! -e "$app/Contents/Frameworks/React.framework"
+          test -e "$app/Contents/Frameworks/hermes.framework"
+          test -e "$app/Contents/Frameworks/ReactNativeDependencies.framework"
+          ! otool -L "$app/Contents/MacOS/RNTesterMacBazelFull" | grep -q React.framework
+          codesign --verify --deep --strict "$app"

.gitignore

@@ -204,3 +204,17 @@ fix_*.patch
 .cursor/rules/nx-rules.mdc
 .github/instructions/nx.instructions.md
 # macOS]
+
+# Generated by the rules_js Berry fork from yarn.lock (not committed)
+/pnpm-lock.yaml
+
+# Berry fork example: generated lock + transient node_modules
+/tools/bazel/berry/example/pnpm-lock.yaml
+tools/bazel/berry/example/node_modules
+tools/bazel/berry/example/.yarn
+
+# Bazel resolution lock (module deps pinned via BCR; pnpm-lock is generated)
+/MODULE.bazel.lock
+
+# Bazel convenience symlinks
+/bazel-*

BUILD.bazel

@@ -0,0 +1,19 @@
+load("@bazel_skylib//rules:common_settings.bzl", "bool_flag")
+load("@npm//:defs.bzl", "npm_link_all_packages")
+
+bool_flag(
+    name = "rn_from_source",
+    build_setting_default = True,
+    visibility = ["//visibility:public"],
+)
+
+config_setting(
+    name = "rn_from_source_enabled",
+    flag_values = {":rn_from_source": "true"},
+    visibility = ["//visibility:public"],
+)
+
+# Links the pnpm-resolved (from the Berry yarn.lock via our fork) node_modules
+# into the Bazel build graph. Downstream JS targets depend on
+# //:node_modules/<pkg>.
+npm_link_all_packages(name = "node_modules")

MODULE.bazel

@@ -0,0 +1,72 @@
+module(
+    name = "react_native_macos_monorepo",
+    version = "0.0.0",
+    compatibility_level = 1,
+)
+
+###############################################################################
+# JavaScript / Node toolchain (aspect-build rules_js)
+###############################################################################
+bazel_dep(name = "aspect_rules_js", version = "3.2.2")
+bazel_dep(name = "aspect_rules_ts", version = "3.8.11")
+bazel_dep(name = "aspect_bazel_lib", version = "2.22.5")
+bazel_dep(name = "bazel_skylib", version = "1.9.0")
+bazel_dep(name = "rules_nodejs", version = "6.7.5")
+
+# Local fork of rules_js: teach `npm_translate_lock` to read the Yarn Berry (v2+)
+# `yarn.lock` directly, so it stays the single source of truth (no committed
+# second lockfile). The patch swaps the `pnpm import` step for our bundled
+# Berry -> pnpm-lock converter (tools/bazel/berry/berry_to_pnpm_lock.mjs) when
+# the input yarn.lock is a Berry lockfile. See docs/bazel.md.
+single_version_override(
+    module_name = "aspect_rules_js",
+    patch_strip = 1,
+    patches = ["//tools/bazel/patches:aspect_rules_js_berry.patch"],
+    version = "3.2.2",
+)
+
+node = use_extension("@rules_nodejs//nodejs:extensions.bzl", "node", dev_dependency = True)
+node.toolchain(node_version = "22.14.0")
+
+npm = use_extension("@aspect_rules_js//npm:extensions.bzl", "npm", dev_dependency = True)
+npm.npm_translate_lock(
+    name = "npm",
+    # The Berry yarn.lock is the single source of truth. Our rules_js patch
+    # converts it to an (uncommitted, gitignored) pnpm-lock.yaml at rule time
+    # before parsing, so update_pnpm_lock (pnpm import) is left off.
+    yarn_lock = "//:yarn.lock",
+    pnpm_lock = "//:pnpm-lock.yaml",
+    update_pnpm_lock = False,
+    verify_node_modules_ignored = "//:.bazelignore",
+    quiet = False,
+)
+use_repo(npm, "npm")
+
+# Self-contained green proof of the Berry fork (see tools/bazel/berry/example).
+npm.npm_translate_lock(
+    name = "npm_berry_example",
+    yarn_lock = "//tools/bazel/berry/example:yarn.lock",
+    pnpm_lock = "//tools/bazel/berry/example:pnpm-lock.yaml",
+    update_pnpm_lock = False,
+    verify_node_modules_ignored = "//:.bazelignore",
+    quiet = False,
+)
+use_repo(npm, "npm_berry_example")
+
+###############################################################################
+# Apple toolchain (rules_apple / rules_swift) — used by the macOS app slice
+###############################################################################
+bazel_dep(name = "rules_apple", version = "4.5.3")
+bazel_dep(name = "rules_swift", version = "3.6.1")
+bazel_dep(name = "apple_support", version = "2.7.0")
+bazel_dep(name = "rules_cc", version = "0.2.17")
+bazel_dep(name = "platforms", version = "1.1.0")
+
+# Expose the SPM-prebuilt React Native XCFrameworks (built by scripts/ios-prebuild.js)
+# to Bazel so the macOS app slice can link them.
+rn_prebuilt = use_extension("//tools/bazel/apple:prebuilt_xcframeworks.bzl", "rn_prebuilt_xcframeworks_extension")
+use_repo(rn_prebuilt, "rn_prebuilt_xcframeworks")
+
+# Canonical header aliases generated directly from the React Native source tree.
+rn_source_headers = use_extension("//tools/bazel/apple:source_headers.bzl", "rn_source_headers_extension")
+use_repo(rn_source_headers, "rn_source_headers")