feat: use dev/prod conditions instead of webpack in exports (#5858)

.size-limit.js

@@ -0,0 +1,78 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+'use strict';
+
+/**
+ * We use this file to configure the size-lmit tool, rather than their simpler
+ * yaml package.json configuration, because we need to override the resolution
+ * of modules to ensure we are pulling in monorepo build products as
+ * dependencies rather than trying to use something stale from node_modules.
+ */
+const glob = require('glob');
+const path = require('node:path');
+const fs = require('fs-extra');
+
+/**
+ * Build a alias map so that we can be sure that we are resolving monorepo
+ * dependencies to their corresponding build products and not some combination
+ * of a build product and a possibly stale/divergent version in node_modules.
+ *
+ * Looks like:
+ *
+ *   {
+ *     lexical: 'packages/lexical/dist/index.js',
+ *     '@lexical/rich-text': 'packages/lexical-rich-text/dist/index.js',
+ *   }
+ *
+ * Currently this alias map points at the cjs version of the build product,
+ * as that is what was measured previously in #3600.
+ */
+const alias = Object.fromEntries(
+  glob('./packages/*/package.json', {sync: true}).flatMap((fn) => {
+    const pkg = fs.readJsonSync(fn);
+    if (!pkg.private) {
+      return Object.entries(pkg.exports).flatMap(([k, v]) => {
+        if (k.endsWith('.js')) {
+          return [];
+        }
+        return [
+          [
+            `${pkg.name}${k.replace(/^\.(\/$)?/, '')}`,
+            path.resolve(path.dirname(fn), 'dist', v.require.default),
+          ],
+        ];
+      });
+    }
+    return [];
+  }),
+);
+
+const extendConfig = {resolve: {alias}};
+const modifyWebpackConfig = (config) => Object.assign(config, extendConfig);
+
+function sizeLimitConfig(pkg) {
+  return {
+    path: alias[pkg],
+    modifyWebpackConfig,
+  };
+}
+
+/**
+ * These are the packages that were measured previously in #3600
+ * We could consider adding more packages and/or also measuring
+ * other build combinations such as esbuild/webpack, mjs/cjs, dev/prod, etc.
+ *
+ * The current configuration measures only: webpack + cjs + prod.
+ *
+ * In order to also measure dev, we would want to change the size script in
+ * package.json to run build-release instead of build-prod so both
+ * dev and prod artifacts would be available.
+ */
+module.exports = ['lexical', '@lexical/rich-text', '@lexical/plain-text'].map(
+  sizeLimitConfig,
+);