fix(fetch) handle 100 continue (#5496)

* handle 100 continue

* move comment

* cleanup

* fmt

2 files changed, 69 insertions, 1 deletions

diff --git a/src/http_client_async.zig b/src/http_client_async.zig
index 79fe74899..b3c06df56 100644
--- a/src/http_client_async.zig
+++ b/src/http_client_async.zig
@@ -2637,6 +2637,14 @@ pub fn onData(this: *HTTPClient, comptime is_ssl: bool, incoming_data: []const u
             this.state.pending_response = response;
 
             var body_buf = to_read[@min(@as(usize, @intCast(response.bytes_read)), to_read.len)..];
+            // handle the case where we have a 100 Continue
+            if (response.status_code == 100) {
+                // we still can have the 200 OK in the same buffer sometimes
+                if (body_buf.len > 0) {
+                    this.onData(is_ssl, body_buf, ctx, socket);
+                }
+                return;
+            }
 
             var deferred_redirect: ?*URLBufferPool.Node = null;
             const can_continue = this.handleResponseMetadata(
@@ -3399,6 +3407,7 @@ pub fn handleResponseMetadata(
         this.proxy_tunneling = false;
     }
 
+    // if is no redirect or if is redirect == "manual" just proceed
     const is_redirect = response.status_code >= 300 and response.status_code <= 399;
     if (is_redirect) {
         if (this.redirect_type == FetchRedirect.follow and location.len > 0 and this.remaining_redirect_count > 0) {
@@ -3513,7 +3522,6 @@ pub fn handleResponseMetadata(
         }
     }
 
-    // if is no redirect or if is redirect == "manual" just proceed
     this.state.response_stage = if (this.state.transfer_encoding == .chunked) .body_chunk else .body;
     const content_length = this.state.content_length orelse 0;
     // if no body is expected we should stop processing
diff --git a/test/js/web/fetch/fetch.test.ts b/test/js/web/fetch/fetch.test.ts
index 4ef5d7bba..fc4ce7a18 100644
--- a/test/js/web/fetch/fetch.test.ts
+++ b/test/js/web/fetch/fetch.test.ts
@@ -5,6 +5,7 @@ import { mkfifo } from "mkfifo";
 import { tmpdir } from "os";
 import { join } from "path";
 import { gc, withoutAggressiveGC, gcTick } from "harness";
+import net from "net";
 
 const tmp_dir = mkdtempSync(join(realpathSync(tmpdir()), "fetch.test"));
 
@@ -1415,3 +1416,62 @@ it("cloned response headers are independent after accessing", () => {
   cloned.headers.set("content-type", "text/plain");
   expect(response.headers.get("content-type")).toBe("text/html; charset=utf-8");
 });
+
+it("should work with http 100 continue", async () => {
+  let server: net.Server | undefined;
+  try {
+    server = net.createServer(socket => {
+      socket.on("data", data => {
+        const lines = data.toString().split("\r\n");
+        for (const line of lines) {
+          if (line.length == 0) {
+            socket.write("HTTP/1.1 100 Continue\r\n\r\n");
+            socket.write("HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: 13\r\n\r\nHello, World!");
+            break;
+          }
+        }
+      });
+    });
+
+    const { promise: start, resolve } = Promise.withResolvers();
+    server.listen(8080, resolve);
+
+    await start;
+
+    const address = server.address() as net.AddressInfo;
+    const result = await fetch(`http://localhost:${address.port}`).then(r => r.text());
+    expect(result).toBe("Hello, World!");
+  } finally {
+    server?.close();
+  }
+});
+
+it("should work with http 100 continue on the same buffer", async () => {
+  let server: net.Server | undefined;
+  try {
+    server = net.createServer(socket => {
+      socket.on("data", data => {
+        const lines = data.toString().split("\r\n");
+        for (const line of lines) {
+          if (line.length == 0) {
+            socket.write(
+              "HTTP/1.1 100 Continue\r\n\r\nHTTP/1.1 200 OK\r\nContent-Type: text/plain\r\nContent-Length: 13\r\n\r\nHello, World!",
+            );
+            break;
+          }
+        }
+      });
+    });
+
+    const { promise: start, resolve } = Promise.withResolvers();
+    server.listen(8080, resolve);
+
+    await start;
+
+    const address = server.address() as net.AddressInfo;
+    const result = await fetch(`http://localhost:${address.port}`).then(r => r.text());
+    expect(result).toBe("Hello, World!");
+  } finally {
+    server?.close();
+  }
+});