Fix tree-shaking (#2339) (closes #2207)

Fixed broken tree-shaking caused by missing links to corresponding ESM.

scripts/build/packages.js

@@ -18,18 +18,23 @@ const rootPath =
 
 const extraModules = [
   { fullPath: './src/fp/index.js' },
-  { fullPath: './src/locale/index.js' }
+  { fullPath: './src/locale/index.js' },
 ]
 
-const initialPackages = getInitialPackages()
+writePackages()
 
-listAll()
-  .then(modules =>
-    Promise.all(modules.map(module => writePackage(module.fullPath)))
+async function writePackages() {
+  const initialPackages = await getInitialPackages()
+  const modules = await listAll()
+  await Promise.all(
+    modules.map(async (module) =>
+      writePackage(module.fullPath, initialPackages[module.fullPath])
+    )
   )
-  .then('package.json files are generated')
+  console.log('package.json files are generated')
+}
 
-function writePackage(fullPath) {
+function writePackage(fullPath, initialPackage) {
   const dirPath = path.dirname(fullPath)
   const typingsRelativePath = path.relative(dirPath, `./src/typings.d.ts`)
   const packagePath = path.resolve(
@@ -40,8 +45,8 @@ function writePackage(fullPath) {
   return writeFile(
     packagePath,
     JSON.stringify(
-      Object.assign({ sideEffects: false }, initialPackages[fullPath] || {}, {
-        typings: typingsRelativePath
+      Object.assign({ sideEffects: false }, initialPackage || {}, {
+        typings: typingsRelativePath,
       }),
       null,
       2
@@ -79,7 +84,7 @@ async function listAll() {
     .concat(extraModules)
     .reduce((acc, module) => {
       const esmModule = Object.assign({}, module, {
-        fullPath: module.fullPath.replace('./src/', './src/esm/')
+        fullPath: module.fullPath.replace('./src/', './src/esm/'),
       })
       return acc.concat([module, esmModule])
     }, [])