fix(js-runtime): set content-length header for POST/PUT with null body (

#928)

.changeset/breezy-cycles-glow.md

@@ -0,0 +1,7 @@
+---
+'@lagon/js-runtime': patch
+'@lagon/cli': patch
+'@lagon/serverless': patch
+---
+
+Set content-length header to 0 when body is null and method POST or PUT in `fetch()`

crates/runtime/tests/fetch.rs

@@ -607,3 +607,45 @@ async fn fetch_https() {
     )
     .await;
 }
+
+#[tokio::test]
+async fn fetch_set_content_length() {
+    utils::setup();
+    let server = Server::run();
+    server.expect(
+        Expectation::matching(all_of![
+            any_of![
+                request::method_path("POST", "/"),
+                request::method_path("PUT", "/")
+            ],
+            request::headers(contains(("content-length", "0")))
+        ])
+        .times(2)
+        .respond_with(status_code(200)),
+    );
+    let url = server.url("/");
+
+    let (send, receiver) = utils::create_isolate(IsolateOptions::new(format!(
+        "export async function handler() {{
+    await fetch('{url}', {{
+        method: 'POST',
+    }});
+
+    await fetch('{url}', {{
+        method: 'PUT',
+    }});
+
+    return new Response('Ok');
+}}"
+    )));
+    send(Request::default());
+
+    utils::assert_response(
+        &receiver,
+        Response::builder()
+            .header(CONTENT_TYPE, "text/plain;charset=UTF-8")
+            .body("Ok".into())
+            .unwrap(),
+    )
+    .await;
+}

packages/js-runtime/src/runtime/http/fetch.ts

@@ -1,6 +1,8 @@
 (globalThis => {
   const isHeadersObject = (headers?: HeadersInit): headers is Headers => !!headers && 'entries' in headers;
 
+  const FORCE_0_CONTENT_LENGTH_METHODS = ['POST', 'PUT'];
+
   globalThis.fetch = async (input, init) => {
     let headers: Map<string, string> | undefined = undefined;
 
@@ -29,6 +31,14 @@
       }
     }
 
+    if (body === undefined && init?.method && FORCE_0_CONTENT_LENGTH_METHODS.includes(init.method)) {
+      if (!headers) {
+        headers = new Map();
+      }
+
+      headers?.set('content-length', '0');
+    }
+
     const checkAborted = () => {
       if (init?.signal?.aborted) {
         throw new Error('Aborted');