[fix] handle missing server file for an action request

.changeset/witty-spies-occur.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/kit': patch
+---
+
+fix `enhance` error message when form action doesn't exist or csrf is enabled

packages/kit/src/runtime/server/index.js

@@ -17,6 +17,7 @@ import { redirect_json_response, render_data } from './data/index.js';
 import { add_cookies_to_headers, get_cookies } from './cookie.js';
 import { create_fetch } from './fetch.js';
 import { Redirect } from '../control.js';
+import { error, json } from '../../exports/index.js';
 
 /* global __SVELTEKIT_ADAPTER_NAME__ */
 
@@ -40,9 +41,11 @@ export async function respond(request, options, state) {
 			is_form_content_type(request);
 
 		if (forbidden) {
-			return new Response(`Cross-site ${request.method} form submissions are forbidden`, {
-				status: 403
-			});
+			const csrf_error = error(403, `Cross-site ${request.method} form submissions are forbidden`);
+			if (request.headers.get('accept') === 'application/json') {
+				return json(csrf_error.body, { status: csrf_error.status });
+			}
+			return new Response(csrf_error.body.message, { status: csrf_error.status });
 		}
 	}
 

packages/kit/src/runtime/server/page/actions.js

@@ -18,22 +18,31 @@ export function is_action_json_request(event) {
 /**
  * @param {import('types').RequestEvent} event
  * @param {import('types').SSROptions} options
- * @param {import('types').SSRNode['server']} server
+ * @param {import('types').SSRNode['server'] | undefined} server
  */
 export async function handle_action_json_request(event, options, server) {
-	const actions = server.actions;
+	const actions = server?.actions;
 
 	if (!actions) {
-		maybe_throw_migration_error(server);
+		if (server) {
+			maybe_throw_migration_error(server);
+		}
 		// TODO should this be a different error altogether?
-		return new Response('POST method not allowed. No actions exist for this page', {
-			status: 405,
-			headers: {
-				// https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/405
-				// "The server must generate an Allow header field in a 405 status code response"
-				allow: 'GET'
+		const no_actions_error = error(405, 'POST method not allowed. No actions exist for this page');
+		return action_json(
+			{
+				type: 'error',
+				error: await handle_error_and_jsonify(event, options, no_actions_error)
+			},
+			{
+				status: no_actions_error.status,
+				headers: {
+					// https://developer.mozilla.org/en-US/docs/Web/HTTP/Status/405
+					// "The server must generate an Allow header field in a 405 status code response"
+					allow: 'GET'
+				}
 			}
-		});
+		);
 	}
 
 	check_named_default_separate(actions);

packages/kit/src/runtime/server/page/index.js

@@ -40,9 +40,7 @@ export async function render_page(event, route, page, options, state, resolve_op
 
 	if (is_action_json_request(event)) {
 		const node = await options.manifest._.nodes[page.leaf]();
-		if (node.server) {
-			return handle_action_json_request(event, options, node.server);
-		}
+		return handle_action_json_request(event, options, node?.server);
 	}
 
 	try {