Fix sizebot (#15771)

The previous naming scheme used the name of the resulting bundle file.
However, there are cases where multiple bundles have the same filename.
This meant whichever bundle finishes last overwrites the previous ones
with the same name.

The updated naming scheme is `bundle-sizes-<CI_NODE_INDEX>.json`.
Instead of generating a separate info file per bundle, it now creates
one per process.

scripts/rollup/build.js

@@ -21,7 +21,7 @@ const useForks = require('./plugins/use-forks-plugin');
 const stripUnusedImports = require('./plugins/strip-unused-imports');
 const extractErrorCodes = require('../error-codes/extract-errors');
 const Packaging = require('./packaging');
-const {asyncCopyTo} = require('./utils');
+const {asyncCopyTo, asyncRimRaf} = require('./utils');
 const codeFrame = require('babel-code-frame');
 const Wrappers = require('./wrappers');
 
@@ -634,6 +634,8 @@ function handleRollupError(error) {
 }
 
 async function buildEverything() {
+  await asyncRimRaf('build');
+
   // Run them serially for better console output
   // and to avoid any potential race conditions.
 

scripts/rollup/consolidateBundleSizes.js

@@ -13,9 +13,9 @@ const filenames = fs.readdirSync(path.join(BUILD_DIR, 'sizes'));
 let bundleSizes = [];
 for (let i = 0; i < filenames.length; i++) {
   const filename = filenames[i];
-  if (filename.endsWith('.size.json')) {
+  if (filename.endsWith('.json')) {
     const json = fs.readFileSync(path.join(BUILD_DIR, 'sizes', filename));
-    bundleSizes.push(JSON.parse(json));
+    bundleSizes.push(...JSON.parse(json).bundleSizes);
   }
 }
 

scripts/rollup/stats.js

@@ -18,22 +18,23 @@ const currentBuildResults = {
 };
 
 function saveResults() {
-  // Write all the bundle sizes to a single JSON file.
-  fs.writeFileSync(
-    BUNDLE_SIZES_FILE_NAME,
-    JSON.stringify(currentBuildResults, null, 2)
-  );
-
-  // Also write each bundle size to a separate file. That way multiple build
-  // processes can run in parallel and generate separate size artifacts.
-  // A downstream job can combine them into a single JSON file.
-  mkdirp.sync('build/sizes');
-  currentBuildResults.bundleSizes.forEach(results => {
+  if (process.env.CIRCLE_NODE_TOTAL) {
+    // In CI, write the bundle sizes to a subdirectory and append the node index
+    // to the filename. A downstream job will consolidate these into a
+    // single file.
+    const nodeIndex = process.env.CIRCLE_NODE_INDEX;
+    mkdirp.sync('build/sizes');
     fs.writeFileSync(
-      join('build', 'sizes', `${results.filename}.size.json`),
-      JSON.stringify(results, null, 2)
+      join('build', 'sizes', `bundle-sizes-${nodeIndex}.json`),
+      JSON.stringify(currentBuildResults, null, 2)
     );
-  });
+  } else {
+    // Write all the bundle sizes to a single JSON file.
+    fs.writeFileSync(
+      BUNDLE_SIZES_FILE_NAME,
+      JSON.stringify(currentBuildResults, null, 2)
+    );
+  }
 }
 
 function fractionalChange(prev, current) {