Support Webpack 4 with a "legacy ESM" artifact

.github/workflows/test.yaml

@@ -16,6 +16,8 @@ jobs:
             src:
               - 'src/**'
               - 'test/**'
+              - '.github/**/*.yaml'
+              - 'tsup.config.ts'
 
   build:
     needs: changes

package.json

@@ -24,7 +24,7 @@
     "Andrew Clark <acdlite@me.com> (https://github.com/acdlite)"
   ],
   "main": "dist/cjs/redux.cjs",
-  "module": "dist/redux.mjs",
+  "module": "dist/redux.legacy-esm.js",
   "types": "dist/redux.d.ts",
   "exports": {
     "./package.json": "./package.json",
@@ -56,21 +56,7 @@
     "tsc": "tsc"
   },
   "devDependencies": {
-    "@babel/cli": "^7.18.10",
     "@babel/core": "^7.19.0",
-    "@babel/eslint-parser": "^7.18.9",
-    "@babel/node": "^7.18.10",
-    "@babel/plugin-external-helpers": "^7.18.6",
-    "@babel/plugin-proposal-object-rest-spread": "^7.18.9",
-    "@babel/plugin-transform-runtime": "^7.18.10",
-    "@babel/preset-env": "^7.19.0",
-    "@babel/preset-flow": "^7.18.6",
-    "@babel/preset-typescript": "^7.18.6",
-    "@babel/register": "^7.18.9",
-    "@rollup/plugin-babel": "^6",
-    "@rollup/plugin-node-resolve": "^15.0.1",
-    "@rollup/plugin-replace": "^5.0.0",
-    "@rollup/plugin-terser": "^0.4.0",
     "@types/node": "^18.7.16",
     "@typescript-eslint/eslint-plugin": "^5.36.2",
     "@typescript-eslint/parser": "^5.36.2",
@@ -79,30 +65,17 @@
     "eslint": "^8.23.0",
     "eslint-config-react-app": "^7.0.1",
     "eslint-import-resolver-typescript": "^3.5.1",
-    "eslint-plugin-flowtype": "^8.0.3",
     "eslint-plugin-import": "^2.26.0",
-    "eslint-plugin-jsx-a11y": "^6.6.1",
     "eslint-plugin-react": "^7.31.8",
     "eslint-plugin-react-hooks": "^4.6.0",
     "glob": "^8.0.3",
     "netlify-plugin-cache": "^1.0.3",
     "prettier": "^2.7.1",
     "rimraf": "^3.0.2",
-    "rollup": "^3.12.0",
-    "rollup-plugin-typescript2": "^0.34.1",
     "rxjs": "^7.5.6",
     "tsup": "^6.7.0",
     "typescript": "^4.8.3",
     "vitest": "^0.27.2"
   },
-  "npmName": "redux",
-  "npmFileMap": [
-    {
-      "basePath": "/dist/",
-      "files": [
-        "*.js"
-      ]
-    }
-  ],
   "sideEffects": false
 }

tsup.config.ts

@@ -3,6 +3,7 @@ import { defineConfig, Options } from 'tsup'
 import * as babel from '@babel/core'
 import { Plugin } from 'esbuild'
 import { getBuildExtensions } from 'esbuild-extra'
+import fs from 'fs'
 
 // Extract error strings, replace them with error codes, and write messages to a file
 const mangleErrorsTransform: Plugin = {
@@ -42,7 +43,11 @@ export default defineConfig(options => {
       format: ['esm'],
       outExtension: () => ({ js: '.mjs' }),
       dts: true,
-      clean: true
+      clean: true,
+      onSuccess() {
+        // Support Webpack 4 by pointing `"module"` to a file with a `.js` extension
+        fs.copyFileSync('dist/redux.mjs', 'dist/redux.legacy-esm.js')
+      }
     },
     // Browser-ready ESM, production + minified
     {