Fix base not working with server actions (#12280)

Co-authored-by: Fredrik Löwenhamn <fredrik.lowenhamn@gmail.com>

packages/astro/src/actions/runtime/virtual/get-action.ts

@@ -12,7 +12,7 @@ export async function getAction(
 	path: string,
 ): Promise<ActionClient<unknown, ActionAccept, ZodType>> {
 	const pathKeys = path
-		.replace('/_actions/', '')
+		.replace(/^.*\/_actions\//, '')
 		.split('.')
 		.map((key) => decodeURIComponent(key));
 	// @ts-expect-error virtual module

packages/astro/templates/actions.mjs

@@ -92,7 +92,7 @@ async function handleAction(param, path, context) {
 			headers.set('Content-Length', '0');
 		}
 	}
-	const rawResult = await fetch(`/_actions/${path}`, {
+	const rawResult = await fetch(`${import.meta.env.BASE_URL.replace(/\/$/, "")}/_actions/${path}`, {
 		method: 'POST',
 		body,
 		headers,

packages/astro/test/actions.test.js

@@ -466,6 +466,30 @@ describe('Astro Actions', () => {
 	});
 });
 
+it('Base path should be used', async () => {
+	const fixture = await loadFixture({
+		root: './fixtures/actions/',
+		adapter: testAdapter(),
+		base: "/base"
+	});
+	const devServer = await fixture.startDevServer();
+	const formData = new FormData();
+	formData.append('channel', 'bholmesdev');
+	formData.append('comment', 'Hello, World!');
+	const res = await fixture.fetch('/base/_actions/comment', {
+		method: 'POST',
+		body: formData,
+	});
+
+	assert.equal(res.ok, true);
+	assert.equal(res.headers.get('Content-Type'), 'application/json+devalue');
+
+	const data = devalue.parse(await res.text());
+	assert.equal(data.channel, 'bholmesdev');
+	assert.equal(data.comment, 'Hello, World!');
+	await devServer.stop()
+});
+
 /**
  * Follow an expected redirect response.
  *