feat: bundler (esbuild, nextjs) integration tests (#699)

Author: gabrielmfern

integrations/esbuild/.gitignore

@@ -0,0 +1 @@
+index.js

integrations/esbuild/index.ts

@@ -0,0 +1,3 @@
+import { Resend } from 'resend';
+
+new Resend('');

integrations/esbuild/package.json

@@ -0,0 +1,9 @@
+{
+  "dependencies": {
+    "esbuild": "0.25.11",
+    "resend": "../.."
+  },
+  "scripts": {
+    "build": "esbuild ./index.ts --bundle --platform=node --target=node18 --outfile=./index.js"
+  }
+}

integrations/integrations.spec.ts

@@ -0,0 +1,89 @@
+import { spawnSync } from 'node:child_process';
+import fs from 'node:fs';
+import os from 'node:os';
+import path from 'node:path';
+
+describe('integrations', () => {
+  const sdkPath = path.resolve(__dirname, '..');
+
+  beforeAll(() => {
+    const build = spawnSync('pnpm build', {
+      stdio: 'inherit',
+      cwd: path.resolve(__dirname, '..'),
+      shell: true,
+    });
+    if (build.status !== 0) {
+      throw new Error('SDK build failed');
+    }
+  });
+
+  /**
+   * Create an extra temporary copy of the given integration so that there's no `@react-email/render` module resolution from the resend-node's devDependencies
+   *
+   * Also modifies the package.json to point to the SDK with an absolute path.
+   */
+  async function prepareTemporaryIntegrationCopy(integrationPath: string) {
+    const temporaryIntegrationPath = await fs.promises.mkdtemp(
+      path.join(
+        os.tmpdir(),
+        `resend-node-integration-${path.basename(integrationPath)}`,
+      ),
+    );
+    await fs.promises.cp(
+      path.resolve(__dirname, integrationPath),
+      temporaryIntegrationPath,
+      {
+        recursive: true,
+      },
+    );
+
+    const testingLockPackageJson: { dependencies: Record<string, string> } =
+      JSON.parse(
+        await fs.promises.readFile(
+          path.resolve(temporaryIntegrationPath, 'package.json'),
+          'utf8',
+        ),
+      );
+    testingLockPackageJson.dependencies.resend = sdkPath;
+    await fs.promises.writeFile(
+      path.resolve(temporaryIntegrationPath, 'package.json'),
+      JSON.stringify(testingLockPackageJson, null, 2),
+    );
+
+    return temporaryIntegrationPath;
+  }
+
+  test('nextjs', { timeout: 30_000 }, async () => {
+    const temporaryNextAppPath =
+      await prepareTemporaryIntegrationCopy('./nextjs');
+
+    const buildInstall = spawnSync(
+      'npm install --install-links && npm run build',
+      {
+        stdio: 'inherit',
+        cwd: temporaryNextAppPath,
+        shell: true,
+      },
+    );
+    if (buildInstall.status !== 0) {
+      throw new Error('next.js build failed');
+    }
+  });
+
+  test('esbuild', { timeout: 30_000 }, async () => {
+    const temporaryEsbuildAppPath =
+      await prepareTemporaryIntegrationCopy('./esbuild');
+
+    const buildInstall = spawnSync(
+      'npm install --install-links && npm run build',
+      {
+        stdio: 'inherit',
+        cwd: temporaryEsbuildAppPath,
+        shell: true,
+      },
+    );
+    if (buildInstall.status !== 0) {
+      throw new Error('esbuild build failed');
+    }
+  });
+});

integrations/nextjs/.gitignore

@@ -0,0 +1,42 @@
+# See https://help.github.com/articles/ignoring-files/ for more about ignoring files.
+
+# dependencies
+package-lock.json
+/node_modules
+/.pnp
+.pnp.*
+.yarn/*
+!.yarn/patches
+!.yarn/plugins
+!.yarn/releases
+!.yarn/versions
+
+# testing
+/coverage
+
+# next.js
+/.next/
+/out/
+
+# production
+/build
+
+# misc
+.DS_Store
+*.pem
+
+# debug
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+.pnpm-debug.log*
+
+# env files (can opt-in for committing if needed)
+.env*
+
+# vercel
+.vercel
+
+# typescript
+*.tsbuildinfo
+next-env.d.ts

integrations/nextjs/app/route.js

@@ -0,0 +1,7 @@
+import { Resend } from 'resend';
+
+export function GET() {
+  new Resend('');
+
+  return new Response('Hello from this API route!', { status: 200 });
+}

integrations/nextjs/next.config.js

@@ -0,0 +1 @@
+module.exports = {};

integrations/nextjs/package.json

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+{
+  "dependencies": {
+    "next": "15.5.6",
+    "react": "19.2.0",
+    "react-dom": "19.2.0",
+    "resend": "../.."
+  },
+  "scripts": {
+    "build": "next build"
+  }
+}

package.json

@@ -31,11 +31,13 @@
   },
   "scripts": {
     "build": "tsdown src/index.ts --format esm,cjs --dts",
+    "integration:nextjs": "cd ./integrations/nextjs && next build --turbopack",
     "lint": "biome check .",
     "lint:fix": "biome check . --write",
     "prepublishOnly": "pnpm run build",
     "test": "vitest run",
     "test:dev": "cross-env TEST_MODE=dev vitest run",
+    "test:integrations": "vitest run integrations",
     "test:record": "rimraf --glob \"**/__recordings__\" && cross-env TEST_MODE=record vitest run",
     "test:watch": "vitest",
     "typecheck": "tsc --noEmit"