fix: add redirects for routes containing '__data.json' suffix (#5180)

* fix: add redirect for routes containing __data.json suffix

* fix: await for builder.createEntries to complete before writing redirects file

* chore: add changeset entry

* Update tasty-zebras-guess.md

Co-authored-by: Rich Harris <[email protected]>

Author: ericapisani

.changeset/tasty-zebras-guess.md

@@ -0,0 +1,5 @@
+---
+'@sveltejs/adapter-netlify': patch
+---
+
+fix: add redirects for routes containing `__data.json` suffix

packages/adapter-netlify/index.js

@@ -150,7 +150,7 @@ async function generate_edge_functions({ builder }) {
  * @param { boolean } params.split
  * @param { boolean } params.esm
  */
-function generate_lambda_functions({ builder, publish, split, esm }) {
+async function generate_lambda_functions({ builder, publish, split, esm }) {
 	builder.mkdirp('.netlify/functions-internal');
 
 	/** @type {string[]} */
@@ -177,7 +177,7 @@ function generate_lambda_functions({ builder, publish, split, esm }) {
 	if (split) {
 		builder.log.minor('Generating serverless functions...');
 
-		builder.createEntries((route) => {
+		await builder.createEntries((route) => {
 			const parts = [];
 			// Netlify's syntax uses '*' and ':param' as "splats" and "placeholders"
 			// https://docs.netlify.com/routing/redirects/redirect-options/#splats
@@ -211,6 +211,7 @@ function generate_lambda_functions({ builder, publish, split, esm }) {
 					writeFileSync(`.netlify/functions-internal/${name}.js`, fn);
 
 					redirects.push(`${pattern} /.netlify/functions/${name} 200`);
+					redirects.push(`${pattern}/__data.json /.netlify/functions/${name} 200`);
 				}
 			};
 		});