test: ensure PRECHECKS are working for static file handling

tests/01_static_files.test.ts

@@ -477,6 +477,124 @@ Deno.test({
 	}
 });
 
+Deno.test({
+	name: 'allow overriding prechecks',
+	permissions: {
+		env: true,
+		read: true,
+		write: true,
+		net: true
+	},
+
+	sanitizeResources: false,
+	sanitizeOps: false,
+
+	fn: async () => {
+		let test_server_info: EPHEMERAL_SERVER | null = null;
+		const cwd = Deno.cwd();
+
+		const static_file_handler = await import('../handlers/static.ts');
+		const PREVIOUS_PRECHECKS = static_file_handler.PRECHECKS.PUT?.slice(0);
+		try {
+			Deno.chdir('./tests/www');
+			test_server_info = await get_ephemeral_listen_server();
+
+			const PRECHECKS = static_file_handler.PRECHECKS.PUT = PREVIOUS_PRECHECKS ? [...PREVIOUS_PRECHECKS] : [];
+			PRECHECKS.push((request: Request): Response | undefined => {
+				const has_required_header = request.headers.get('x-required-header');
+
+				if (!has_required_header) {
+					return Response.json({
+						error: {
+							message: 'Missing required header.',
+							cause: 'missing_required_header'
+						}
+					}, {
+						status: 400
+					});
+				}
+			});
+
+			const failed_put_body = new FormData();
+			failed_put_body.append(
+				'file',
+				new File(['this is the test content for precheck overrides'], 'test_put_upload_that_should_fail.txt')
+			);
+			const failed_put_response = await fetch(
+				`http://${test_server_info.hostname}:${test_server_info.port}/files/test_put_upload_that_should_fail.txt`,
+				{
+					method: 'PUT',
+					body: failed_put_body
+				}
+			);
+
+			asserts.assert(!failed_put_response.ok);
+
+			const failed_body = await failed_put_response.json();
+			asserts.assert(failed_body);
+			asserts.assert(failed_body.error);
+			asserts.assertEquals(failed_body.error.cause, 'missing_required_header');
+
+			const successful_put_body = new FormData();
+			successful_put_body.append(
+				'file',
+				new File(['this is the test content for precheck overrides'], 'test_put_upload_that_should_not_fail.txt')
+			);
+			const successful_put_response = await fetch(
+				`http://${test_server_info.hostname}:${test_server_info.port}/files/test_put_upload_that_should_not_fail.txt`,
+				{
+					method: 'PUT',
+					headers: {
+						'x-required-header': 'true'
+					},
+					body: successful_put_body
+				}
+			);
+
+			asserts.assert(successful_put_response.ok);
+
+			const successful_body = await successful_put_response.json();
+			asserts.assert(successful_body);
+			asserts.assert(successful_body.written);
+			asserts.assertEquals(
+				successful_body.written[0],
+				`http://${test_server_info.hostname}:${test_server_info.port}/files/test_put_upload_that_should_not_fail.txt`
+			);
+
+			const get_response = await fetch(
+				`http://${test_server_info.hostname}:${test_server_info.port}/files/test_put_upload_that_should_not_fail.txt`,
+				{
+					method: 'GET'
+				}
+			);
+
+			asserts.assert(get_response.ok);
+			asserts.assert(get_response.body);
+
+			const local_download_path = path.join(Deno.cwd(), 'files', 'test_put_upload_that_should_not_fail.txt-downloaded');
+			await ensureFile(local_download_path);
+
+			const file = await Deno.open(local_download_path, { truncate: true, write: true });
+			await get_response.body.pipeTo(file.writable);
+
+			const download_content = await Deno.readTextFile(local_download_path);
+			asserts.assert(download_content);
+			asserts.assertEquals(download_content, 'this is the test content for precheck overrides');
+
+			await Deno.remove(local_download_path);
+			asserts.assert(!fs.existsSync(local_download_path));
+		} finally {
+			if (PREVIOUS_PRECHECKS) {
+				static_file_handler.PRECHECKS.PUT = PREVIOUS_PRECHECKS;
+			}
+			Deno.chdir(cwd);
+			if (test_server_info) {
+				await test_server_info?.server?.stop();
+			}
+		}
+	}
+});
+
 Deno.test({
 	name: 'these methods should not work on static files',
 	permissions: {