feat: Drop legacy webpack v4 support

docs/react/guides/migrating-to-v5.md

@@ -177,6 +177,10 @@ Custom loggers were already deprecated in 4 and have been removed in this versio
 
 We have updated our browserslist to produce a more modern, performant and smaller bundle. You can read about the requirements [here](../installation#requirements).
 
+### Supported Bundlers
+
+We have removed the legacy `.esm.js` output, which was used by bundlers which didn't recognise the modern `.mjs` extension such as Webpack v4. If you are still using Webpack v4, you can continue to use TanStack Query v4, or upgrade to Webpack v5 or another bundler.
+
 ### Private class fields and methods
 
 TanStack Query has always had private fields and methods on classes, but they weren't really private - they were just private in `TypeScript`. We now use [ECMAScript Private class features](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes/Private_class_fields), which means those fields are now truly private and can't be accessed from the outside at runtime.

packages/query-async-storage-persister/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/query-broadcast-client-experimental/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/query-core/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/query-persist-client-core/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/query-sync-storage-persister/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/react-query-devtools/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/react-query-persist-client/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/react-query/package.json

@@ -13,7 +13,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

packages/vue-query/package.json

@@ -17,7 +17,7 @@
   "type": "commonjs",
   "types": "build/lib/index.d.ts",
   "main": "build/lib/index.js",
-  "module": "build/lib/index.esm.js",
+  "module": "build/lib/index.mjs",
   "exports": {
     ".": {
       "types": "./build/lib/index.d.ts",

scripts/getRollupConfig.mjs

@@ -75,7 +75,7 @@ export function buildConfigs(opts) {
     forceBundle: opts.forceBundle || false,
   }
 
-  let builds = [mjs(options), esm(options), cjs(options)]
+  let builds = [mjs(options), cjs(options)]
 
   if (!opts.skipUmdBuild) {
     builds = builds.concat([
@@ -123,42 +123,6 @@ function mjs({ input, external, outputFile, forceDevEnv, forceBundle }) {
   }
 }
 
-/**
- * @param {import('./types').Options} options - Options for building configurations.
- * @returns {import('rollup').RollupOptions}
- */
-function esm({ input, external, outputFile, forceDevEnv, forceBundle }) {
-  /** @type {import('rollup').OutputOptions} */
-  const bundleOutput = {
-    format: 'esm',
-    file: `./build/lib/${outputFile}.esm.js`,
-    sourcemap: true,
-  }
-
-  /** @type {import('rollup').OutputOptions} */
-  const normalOutput = {
-    format: 'esm',
-    dir: `./build/lib`,
-    sourcemap: true,
-    preserveModules: true,
-    entryFileNames: '[name].esm.js',
-  }
-
-  return {
-    // ESM
-    external,
-    input,
-    output: forceBundle ? bundleOutput : normalOutput,
-    plugins: [
-      babelPlugin('legacy'),
-      commonJS(),
-      nodeResolve({ extensions: ['.ts', '.tsx', '.native.ts'] }),
-      forceDevEnv ? forceEnvPlugin('development') : undefined,
-      preserveDirectives(),
-    ],
-  }
-}
-
 /**
  * @param {import('./types').Options} options - Options for building configurations.
  * @returns {import('rollup').RollupOptions}