Set up experimental builds

The experimental builds are packaged exactly like builds in the stable
release channel: same file structure, entry points, and npm package
names. The goal is to match what will eventually be released in stable
as closely as possible, but with additional features turned on.

Versioning and Releasing
------------------------

The experimental builds will be published to the same registry and
package names as the stable ones. However, they will be versioned using
a separate scheme. Instead of semver versions, experimental releases
will receive arbitrary version strings based on their content hashes.
The motivation is to thwart attempts to use a version range to match
against future experimental releases. The only way to install or depend
on an experimental release is to refer to the specific version number.

Building
--------

I did not use the existing feature flag infra to configure the
experimental builds. The reason is because feature flags are designed
to configure a single package. They're not designed to generate multiple
forks of the same package; for each set of feature flags, you must
create a separate package configuration.

Instead, I've added a new build dimension called the **release
channel**. By default, builds use the **stable** channel. There's
also an **experimental** release channel. We have the option to add more
in the future.

There are now two dimensions per artifact: build type (production,
development, or profiling), and release channel (stable or
experimental). These are separate dimensions because they are
combinatorial: there are stable and experimental production builds,
stable and experimental developmenet builds, and so on.

You can add something to an experimental build by gating on
`__EXPERIMENTAL__`, similar to how we use `__DEV__`. Anything inside
these branches will be excluded from the stable builds.
This gives us a low effort way to add experimental behavior in any
package without setting up feature flags or configuring a new package.

Author: acdlite

.circleci/config.yml

@@ -74,6 +74,18 @@ jobs:
       - *run_yarn
       - run: yarn test --maxWorkers=2
 
+  test_source_experimental:
+    docker: *docker
+    environment: *environment
+    steps:
+      - checkout
+      - *restore_yarn_cache
+      - *run_yarn
+      - run:
+          environment:
+            RELEASE_CHANNEL: experimental
+          command: yarn test --maxWorkers=2
+
   test_source_persistent:
     docker: *docker
     environment: *environment
@@ -114,6 +126,30 @@ jobs:
             - dist
             - sizes/*.json
 
+  build_experimental:
+    docker: *docker
+    environment: *environment
+    parallelism: 20
+    steps:
+      - checkout
+      - *restore_yarn_cache
+      - *run_yarn
+      - run:
+          environment:
+            RELEASE_CHANNEL: experimental
+          command: |
+            ./scripts/circleci/add_build_info_json.sh
+            ./scripts/circleci/update_package_versions.sh
+      - run: yarn build
+      - persist_to_workspace:
+          root: build
+          paths:
+            - facebook-www
+            - node_modules
+            - react-native
+            - dist
+            - sizes/*.json
+
   process_artifacts:
     docker: *docker
     environment: *environment
@@ -208,7 +244,7 @@ jobs:
 
 workflows:
   version: 2
-  commit:
+  stable:
     jobs:
       - setup
       - lint:
@@ -247,9 +283,24 @@ workflows:
       - test_dom_fixtures:
           requires:
             - build
-  hourly:
+
+  experimental:
+    jobs:
+      - setup
+      - test_source_experimental:
+          requires:
+            - setup
+      - build_experimental:
+          requires:
+            - setup
+      - process_artifacts:
+          requires:
+            - build_experimental
+
+  fuzz_tests:
     triggers:
       - schedule:
+          # Fuzz tests run hourly
           cron: "0 * * * *"
           filters:
             branches:

.eslintrc.js

@@ -149,6 +149,7 @@ module.exports = {
     spyOnProd: true,
     __PROFILE__: true,
     __UMD__: true,
+    __EXPERIMENTAL__: true,
     trustedTypes: true,
   },
 };

dangerfile.js

@@ -31,6 +31,7 @@ const fetch = require('node-fetch');
 const {generateResultsArray} = require('./scripts/rollup/stats');
 const {existsSync, readFileSync} = require('fs');
 const {exec} = require('child_process');
+const {getArtifactsList} = require('./scripts/release/utils');
 
 if (!existsSync('./build/bundle-sizes.json')) {
   // This indicates the build failed previously.
@@ -118,13 +119,13 @@ function git(args) {
   }
 
   const upstreamRef = danger.github.pr.base.ref;
-  await git(`remote add upstream https://github.com/facebook/react.git`);
+  // await git(`remote add upstream https://github.com/facebook/react.git`);
   await git('fetch upstream');
   const baseCommit = await git(`merge-base HEAD upstream/${upstreamRef}`);
 
   let previousBuildResults = null;
   try {
-    let baseCIBuildId = null;
+    let baseArtifactsInfo = null;
     const statusesResponse = await fetch(
       `https://api.github.com/repos/facebook/react/commits/${baseCommit}/status`
     );
@@ -133,33 +134,26 @@ function git(args) {
       warn(`Base commit is broken: ${baseCommit}`);
       return;
     }
-    for (let i = 0; i < statuses.length; i++) {
+    findArtifactsInfo: for (let i = 0; i < statuses.length; i++) {
       const status = statuses[i];
-      // This must match the name of the CI job that creates the build artifacts
-      if (status.context === 'ci/circleci: process_artifacts') {
-        if (status.state === 'success') {
-          baseCIBuildId = /\/facebook\/react\/([0-9]+)/.exec(
-            status.target_url
-          )[1];
-          break;
-        }
-        if (status.state === 'pending') {
-          warn(`Build job for base commit is still pending: ${baseCommit}`);
-          return;
-        }
+      // CircleCI doesn't have an API to retrieve a workflow ID for a given
+      // commit, so we have to resort to some trickery. Use the statuses
+      // endpoint to find a recent status that matches the "stable" workflow.
+      // It must be a job that doesn't also run in the "experimental" workflow.
+      if (status.context === 'ci/circleci: build') {
+        // Scrape the job ID from the url.
+        const buildJobID = /\/facebook\/react\/([0-9]+)/.exec(
+          status.target_url
+        )[1];
+        baseArtifactsInfo = await getArtifactsList(buildJobID);
       }
     }
 
-    if (baseCIBuildId === null) {
+    if (baseArtifactsInfo === null) {
       warn(`Could not find build artifacts for base commit: ${baseCommit}`);
       return;
     }
 
-    const baseArtifactsInfoResponse = await fetch(
-      `https://circleci.com/api/v1.1/project/github/facebook/react/${baseCIBuildId}/artifacts`
-    );
-    const baseArtifactsInfo = await baseArtifactsInfoResponse.json();
-
     for (let i = 0; i < baseArtifactsInfo.length; i++) {
       const info = baseArtifactsInfo[i];
       if (info.path === 'home/circleci/project/build/bundle-sizes.json') {

packages/shared/ReactFeatureFlags.js

@@ -52,7 +52,7 @@ export const disableInputAttributeSyncing = false;
 
 // These APIs will no longer be "unstable" in the upcoming 16.7 release,
 // Control this behavior with a flag to support 16.6 minor releases in the meanwhile.
-export const enableStableConcurrentModeAPIs = false;
+export const enableStableConcurrentModeAPIs = __EXPERIMENTAL__;
 
 export const warnAboutShorthandPropertyCollision = false;
 

scripts/flow/environment.js

@@ -11,6 +11,7 @@
 
 declare var __PROFILE__: boolean;
 declare var __UMD__: boolean;
+declare var __EXPERIMENTAL__: boolean;
 
 declare var __REACT_DEVTOOLS_GLOBAL_HOOK__: any; /*?{
   inject: ?((stuff: Object) => void)

scripts/jest/setupEnvironment.js

@@ -7,6 +7,7 @@ if (NODE_ENV !== 'development' && NODE_ENV !== 'production') {
 global.__DEV__ = NODE_ENV === 'development';
 global.__PROFILE__ = NODE_ENV === 'development';
 global.__UMD__ = false;
+global.__EXPERIMENTAL__ = process.env.RELEASE_CHANNEL === 'experimental';
 
 if (typeof window !== 'undefined') {
   global.requestIdleCallback = function(callback) {

scripts/release/prepare-canary-commands/get-latest-master-build-number.js

@@ -13,6 +13,7 @@ const run = async () => {
     entry =>
       entry.branch === 'master' &&
       entry.status === 'success' &&
+      entry.workflows.workflow_name === 'build_stable' &&
       entry.workflows.job_name === 'process_artifacts'
   ).build_num;
 

scripts/release/utils.js

@@ -78,12 +78,16 @@ const getArtifactsList = async buildID => {
 const getBuildInfo = async () => {
   const cwd = join(__dirname, '..', '..');
 
+  const isExperimental = process.env.RELEASE_CHANNEL === 'experimental';
+
   const branch = await execRead('git branch | grep \\* | cut -d " " -f2', {
     cwd,
   });
   const commit = await execRead('git show -s --format=%h', {cwd});
   const checksum = await getChecksumForCurrentRevision(cwd);
-  const version = `0.0.0-${commit}`;
+  const version = isExperimental
+    ? `0.0.0-experimental-${commit}`
+    : `0.0.0-${commit}`;
 
   // Only available for Circle CI builds.
   // https://circleci.com/docs/2.0/env-vars/
@@ -94,7 +98,9 @@ const getBuildInfo = async () => {
   const packageJSON = await readJson(
     join(cwd, 'packages', 'react', 'package.json')
   );
-  const reactVersion = `${packageJSON.version}-canary-${commit}`;
+  const reactVersion = isExperimental
+    ? `${packageJSON.version}-experimental-canary-${commit}`
+    : `${packageJSON.version}-canary-${commit}`;
 
   return {branch, buildNumber, checksum, commit, reactVersion, version};
 };

scripts/rollup/build.js

@@ -304,7 +304,8 @@ function getPlugins(
   bundleType,
   globalName,
   moduleType,
-  pureExternalModules
+  pureExternalModules,
+  isExperimentalBuild
 ) {
   const findAndRecordErrorCodes = extractErrorCodes(errorCodeOpts);
   const forks = Modules.getForks(bundleType, entry, moduleType);
@@ -362,6 +363,7 @@ function getPlugins(
       __PROFILE__: isProfiling || !isProduction ? 'true' : 'false',
       __UMD__: isUMDBundle ? 'true' : 'false',
       'process.env.NODE_ENV': isProduction ? "'production'" : "'development'",
+      __EXPERIMENTAL__: isExperimentalBuild,
     }),
     // We still need CommonJS for external deps like object-assign.
     commonjs(),
@@ -485,6 +487,8 @@ async function createBundle(bundle, bundleType) {
     module => !importSideEffects[module]
   );
 
+  const isExperimentalBuild = process.env.RELEASE_CHANNEL === 'experimental';
+
   const rollupConfig = {
     input: resolvedEntry,
     treeshake: {
@@ -508,7 +512,8 @@ async function createBundle(bundle, bundleType) {
       bundleType,
       bundle.global,
       bundle.moduleType,
-      pureExternalModules
+      pureExternalModules,
+      isExperimentalBuild
     ),
     // We can't use getters in www.
     legacy: