fix(NODE-5025): no type definitions for es module (#563)

Author: nbbeeken

Diff for: package.json

@@ -77,8 +77,14 @@
   "main": "./lib/bson.cjs",
   "module": "./lib/bson.mjs",
   "exports": {
-    "import": "./lib/bson.mjs",
-    "require": "./lib/bson.cjs",
+    "import": {
+      "types": "./bson.d.ts",
+      "default": "./lib/bson.mjs"
+    },
+    "require": {
+      "types": "./bson.d.ts",
+      "default": "./lib/bson.cjs"
+    },
     "react-native": "./lib/bson.cjs",
     "browser": "./lib/bson.mjs"
   },

Diff for: test/node/exports.test.ts

@@ -1,6 +1,8 @@
 import { expect } from 'chai';
 import * as BSON from '../register-bson';
 import { sorted, byStrings } from './tools/utils';
+import { readFile } from 'fs/promises';
+import { resolve } from 'path';
 
 const EXPECTED_EXPORTS = [
   // This is our added web indicator not a real export but a small exception for this test.
@@ -53,4 +55,43 @@ describe('bson entrypoint', () => {
     expect(BSON.EJSON).to.be.frozen;
     expect(Object.getPrototypeOf(BSON.EJSON)).to.be.null;
   });
+
+  context('package.json entrypoint', () => {
+    let pkg: typeof import('../../package.json');
+    before(async () => {
+      pkg = await readFile(resolve(__dirname, '../../package.json'), {
+        encoding: 'utf8'
+        // JSON.parse will preserve key order
+      }).then(c => JSON.parse(c));
+    });
+
+    it('maintains the order of keys in exports conditions', async () => {
+      expect(pkg).property('exports').is.a('object');
+      expect(pkg).nested.property('exports.import').is.a('object');
+      expect(pkg).nested.property('exports.require').is.a('object');
+
+      expect(
+        Object.keys(pkg.exports),
+        'Order matters in the exports fields. import/require need to proceed the "bundler" targets (RN/browser) and react-native MUST proceed browser'
+      ).to.deep.equal(['import', 'require', 'react-native', 'browser']);
+
+      // https://www.typescriptlang.org/docs/handbook/release-notes/typescript-4-7.html#packagejson-exports-imports-and-self-referencing
+      expect(
+        Object.keys(pkg.exports.import),
+        'TS docs say that `types` should ALWAYS proceed `default`'
+      ).to.deep.equal(['types', 'default']);
+      expect(
+        Object.keys(pkg.exports.require),
+        'TS docs say that `types` should ALWAYS proceed `default`'
+      ).to.deep.equal(['types', 'default']);
+
+      expect(Object.keys(pkg['compass:exports'])).to.deep.equal(['import', 'require']);
+    });
+
+    it('has the equivalent "bson.d.ts" value for all "types" specifiers', () => {
+      expect(pkg).property('types', 'bson.d.ts');
+      expect(pkg).nested.property('exports.import.types', './bson.d.ts');
+      expect(pkg).nested.property('exports.require.types', './bson.d.ts');
+    });
+  });
 });