build(next-drupal): add .d.cts type definition files

packages/next-drupal/.npmignore

@@ -1,4 +1,5 @@
 /coverage
 /CHANGELOG.md
+/postBuild.js
 /tests
 /tsconfig.json

packages/next-drupal/package.json

@@ -7,6 +7,18 @@
   "type": "module",
   "main": "dist/index.cjs",
   "module": "dist/index.modern.js",
+  "exports": {
+    ".": {
+      "import": {
+        "types": "./dist/index.d.ts",
+        "default": "./dist/index.modern.js"
+      },
+      "require": {
+        "types": "./dist/index.d.cts",
+        "default": "./dist/index.cjs"
+      }
+    }
+  },
   "types": "dist/index.d.ts",
   "license": "MIT",
   "publishConfig": {
@@ -18,6 +30,7 @@
   },
   "scripts": {
     "prepare": "microbundle --no-compress --jsx React.createElement --format modern,cjs",
+    "postprepare": "node postBuild.js",
     "dev": "microbundle watch --no-compress --jsx React.createElement --format modern,cjs",
     "test": "jest"
   },

packages/next-drupal/postBuild.js

@@ -0,0 +1,22 @@
+import { readdir, copyFile } from "node:fs/promises"
+
+const files = await readdir("./dist")
+const tasks = []
+for (const file of files) {
+  if (file.endsWith(".modern.js")) {
+    const base = file.replace(/\.modern\.js$/, "")
+
+    // Make a duplicate of the type definitions.
+    //
+    // From the TypeScript docs:
+    //
+    // "It’s important to note that the CommonJS entrypoint and the ES module
+    // entrypoint each needs its own declaration file, even if the contents are
+    // the same between them."
+    //
+    // @see https://www.typescriptlang.org/docs/handbook/esm-node.html#packagejson-exports-imports-and-self-referencing
+    tasks.push(copyFile(`./dist/${base}.d.ts`, `./dist/${base}.d.cts`))
+  }
+}
+await Promise.all(tasks)
+console.log(`Created unique *.d.cts files for CommonJS build.`)