fix: handle JSON bodies for proxied POST, PUT, DELETE APIs

Fixes an issue where proxied[1] APIs that took JSON content
on POST, PUT or DELETE would fail with a timeout.

The cause was a combination of when the Podium plugin runs in
Fastify's lifecycle[2], that Fastify ships a built-in content
parser for JSON[3], and that our proxy depended on the request
ReadableStream emitting data in order to work.

Our proxy would end up coming in too late, after the request
stream had been consumed.

The fix is to remove the content type parser for proxied routes,
since we in any case aren't interested in the request contents
at the layout level.

[1]: https://podium-lib.io/docs/guides/proxying
[2]: https://fastify.dev/docs/latest/Reference/Lifecycle/
[3]: https://fastify.dev/docs/latest/Reference/ContentTypeParser/

Author: wkillerud

lib/layout-plugin.js

@@ -78,6 +78,12 @@ export default fp(
                 '/*',
             );
 
+            // Remove the built-in application/json parser in Fastify from
+            // the proxy routes instance, otherwise the request stream is
+            // already consumed at this point when we try to proxy it,
+            // leading to failing requests (timeouts).
+            instance.removeAllContentTypeParsers();
+
             // Allow all content types for proxy requests
             // https://github.com/fastify/fastify/blob/master/docs/ContentTypeParser.md#catch-all
             instance.addContentTypeParser('*', (req, payload, cb) => {

tests/layout-plugin.test.js

@@ -143,7 +143,43 @@ tap.test(
 );
 
 tap.test(
-    'POST to "proxy" url - should proxy the request to the Podlets target endpoint',
+    'POST to "proxy" url - should proxy the request to the Podlets target endpoint for application/json',
+    async (t) => {
+        const podlet = new PodletServer();
+        const service = await podlet.listen();
+
+        const layout = new Server(service);
+        const address = await layout.listen();
+
+        // Make sure layout has manifest so proxy endpoints are mounted
+        await request({ address, pathname: '/' });
+
+        // Request proxy endpoint
+        const result = await fetch(
+            new URL('/podium-resource/component/localApi', address),
+            {
+                body: JSON.stringify({
+                    message: 'Message for proxied localApi',
+                }),
+                method: 'POST',
+                headers: {
+                    'content-type': 'application/json',
+                },
+            },
+        );
+
+        const body = await result.json();
+        t.equal(body.payload, '{"message":"Message for proxied localApi"}');
+        t.equal(body.body, 'POST proxy target');
+
+        await layout.close();
+        await podlet.close();
+        t.end();
+    },
+);
+
+tap.test(
+    'POST to "proxy" url - should proxy the request to the Podlets target endpoint for application/x-www-form-urlencoded',
     async (t) => {
         const podlet = new PodletServer();
         const service = await podlet.listen();