feat(NODE-7097): adopt built-in zstd support

src/deps.ts

@@ -1,3 +1,5 @@
+import * as zlib from 'zlib';
+
 import { type Stream } from './cmap/connect';
 import { MongoMissingDependencyError } from './error';
 import type { Callback } from './utils';
@@ -60,15 +62,49 @@ type ZStandardLib = {
 
 export type ZStandard = ZStandardLib | { kModuleError: MongoMissingDependencyError };
 
+function getBuiltInZstdLibrary(): ZStandardLib | null {
+  if (typeof zlib.zstdCompress !== 'function' || typeof zlib.zstdDecompress !== 'function') {
+    return null;
+  }
+
+  return {
+    compress(buf: Uint8Array, level?: number): Promise<Uint8Array> {
+      return new Promise((resolve, reject) => {
+        zlib.zstdCompress(
+          buf,
+          level == null ? {} : { params: { [zlib.constants.ZSTD_c_compressionLevel]: level } },
+          (error, result) => {
+            if (error) return reject(error);
+            resolve(result);
+          }
+        );
+      });
+    },
+    decompress(buf: Uint8Array): Promise<Uint8Array> {
+      return new Promise((resolve, reject) => {
+        zlib.zstdDecompress(buf, (error, result) => {
+          if (error) return reject(error);
+          resolve(result);
+        });
+      });
+    }
+  };
+}
+
 export function getZstdLibrary(): ZStandardLib | { kModuleError: MongoMissingDependencyError } {
+  const builtInZstdLibrary = getBuiltInZstdLibrary();
+  if (builtInZstdLibrary != null) {
+    return builtInZstdLibrary;
+  }
+
   let ZStandard: ZStandardLib | { kModuleError: MongoMissingDependencyError };
   try {
     // eslint-disable-next-line @typescript-eslint/no-require-imports
     ZStandard = require('@mongodb-js/zstd');
   } catch (error) {
     ZStandard = makeErrorModule(
       new MongoMissingDependencyError(
-        'Optional module `@mongodb-js/zstd` not found. Please install it to enable zstd compression',
+        'Built-in zstd support is unavailable and optional module `@mongodb-js/zstd` not found. Please use Node.js 22.15.0+ or install `@mongodb-js/zstd` to enable zstd compression',
         { cause: error, dependencyName: 'zstd' }
       )
     );

test/unit/assorted/optional_require.test.ts

@@ -1,6 +1,7 @@
 import { expect } from 'chai';
 import { existsSync } from 'fs';
 import { resolve } from 'path';
+import * as zlib from 'zlib';
 
 import {
   AuthContext,
@@ -16,6 +17,32 @@ function moduleExistsSync(moduleName) {
 }
 
 describe('optionalRequire', function () {
+  describe('Zstandard', function () {
+    it('supports built-in zstd when the addon is not installed', async function () {
+      const moduleName = '@mongodb-js/zstd';
+      if (moduleExistsSync(moduleName)) {
+        return this.skip();
+      }
+
+      const error = await compress(
+        { zlibCompressionLevel: 0, agreedCompressor: 'zstd' },
+        Buffer.from('test', 'utf8')
+      ).then(
+        () => null,
+        e => e
+      );
+
+      const hasBuiltInZstd =
+        typeof zlib.zstdCompress === 'function' && typeof zlib.zstdDecompress === 'function';
+
+      if (hasBuiltInZstd) {
+        expect(error).to.equal(null);
+      } else {
+        expect(error).to.be.instanceOf(MongoMissingDependencyError);
+      }
+    });
+  });
+
   describe('Snappy', function () {
     it('should error if not installed', async function () {
       const moduleName = 'snappy';

test/unit/cmap/wire_protocol/compression.test.ts

@@ -1,4 +1,3 @@
-import * as zstd from '@mongodb-js/zstd';
 import { expect } from 'chai';
 
 import { compress, Compressor, decompress } from '../../../mongodb';
@@ -13,8 +12,8 @@ describe('compression', function () {
 
         it('compresses the data', async function () {
           const data = await compress(options, buffer);
-          // decompress throws if the message is not zstd compresed
-          expect(await zstd.decompress(data)).to.deep.equal(buffer);
+          expect(data).to.not.deep.equal(buffer);
+          expect(await decompress(Compressor.zstd, data)).to.deep.equal(buffer);
         });
       });
     });