Adds support base64 encoding in Netlify Functions (#3592)

* Adding support for base64 encoded responses in Netlify Functions

* chore: add changeset

* removing the regex check for a more simple header-based check

* nit: cleaning up the readme a bit

3 files changed, 86 insertions, 0 deletions

diff --git a/packages/integrations/netlify/test/functions/base64-response.test.js b/packages/integrations/netlify/test/functions/base64-response.test.js
new file mode 100644
index 000000000..10d43b046
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/base64-response.test.js
@@ -0,0 +1,64 @@
+import { expect } from 'chai';
+import { loadFixture, testIntegration } from './test-utils.js';
+import netlifyAdapter from '../../dist/index.js';
+
+describe('Base64 Responses', () => {
+	/** @type {import('../../../astro/test/test-utils').Fixture} */
+	let fixture;
+
+	before(async () => {
+		fixture = await loadFixture({
+			root: new URL('./fixtures/base64-response/', import.meta.url).toString(),
+			experimental: {
+				ssr: true,
+			},
+			adapter: netlifyAdapter({
+				dist: new URL('./fixtures/base64-response/dist/', import.meta.url),
+				binaryMediaTypes: ['font/otf']
+			}),
+			site: `http://example.com`,
+			integrations: [testIntegration()],
+		});
+		await fixture.build();
+	});
+
+	it('Can return base64 encoded strings', async () => {
+		const entryURL = new URL(
+			'./fixtures/base64-response/.netlify/functions-internal/entry.mjs',
+			import.meta.url
+		);
+		const { handler } = await import(entryURL);
+		const resp = await handler({
+			httpMethod: 'GET',
+			headers: {},
+			rawUrl: 'http://example.com/image',
+			body: '{}',
+			isBase64Encoded: false,
+		});
+		expect(resp.statusCode, 'successful response').to.equal(200);
+		expect(resp.isBase64Encoded, 'includes isBase64Encoded flag').to.be.true;
+
+		const buffer = Buffer.from(resp.body, 'base64');
+		expect(buffer.toString(), 'decoded base64 string matches').to.equal('base64 test string');
+	});
+
+	it('Can define custom binaryMediaTypes', async () => {
+		const entryURL = new URL(
+			'./fixtures/base64-response/.netlify/functions-internal/entry.mjs',
+			import.meta.url
+		);
+		const { handler } = await import(entryURL);
+		const resp = await handler({
+			httpMethod: 'GET',
+			headers: {},
+			rawUrl: 'http://example.com/font',
+			body: '{}',
+			isBase64Encoded: false,
+		});
+		expect(resp.statusCode, 'successful response').to.equal(200);
+		expect(resp.isBase64Encoded, 'includes isBase64Encoded flag').to.be.true;
+
+		const buffer = Buffer.from(resp.body, 'base64');
+		expect(buffer.toString(), 'decoded base64 string matches').to.equal('base64 test font');
+	});
+});
diff --git a/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/font.js b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/font.js
new file mode 100644
index 000000000..3ec4c8364
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/font.js
@@ -0,0 +1,11 @@
+
+export function get() {
+	const buffer = Buffer.from('base64 test font', 'utf-8')
+
+  return new Response(buffer, {
+    status: 200,
+		headers: {
+			'Content-Type': 'font/otf'
+		}
+  });
+}
diff --git a/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/image.js b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/image.js
new file mode 100644
index 000000000..ca3b4d9d3
--- /dev/null
+++ b/packages/integrations/netlify/test/functions/fixtures/base64-response/src/pages/image.js
@@ -0,0 +1,11 @@
+
+export function get() {
+	const buffer = Buffer.from('base64 test string', 'utf-8')
+
+  return new Response(buffer, {
+    status: 200,
+		headers: {
+			'content-type': 'image/jpeg;foo=foo'
+		}
+  });
+}