fix(cdp): implement Target.sendMessageToTarget for headless_chrome (#26) (#83)

headless_chrome (and older Puppeteer) wrap every CDP call inside
Target.sendMessageToTarget. Obscura was returning "Unknown Target
method" for the wrapper, which broke navigation through the high-level
client API even though the WebSocket itself connected.

Add a wrapper-level handler that:
1. Parses the inner JSON-encoded CDP request from params.message
2. Recursively dispatches it (boxed future to sidestep async-fn
   recursion limits) using the wrapper's sessionId so routing works
3. Re-emits the inner response as a Target.receivedMessageFromTarget
   event — the legacy contract these clients listen on instead of
   correlating responses by id
4. Returns {} for the wrapper itself

This addresses the headless_chrome leg of #26. The chromiumoxide
"data did not match any variant of untagged enum Message" decode
failure is a separate event/response shape issue — needs a focused
investigation against a chromiumoxide repro that's not in the issue,
so it's left out of this PR.

Generated by Ora Studio
Vibe coded by ousamabenyounes

Co-authored-by: Ora Studio <[email protected]>

crates/obscura-cdp/src/dispatch.rs

@@ -121,6 +121,14 @@ impl CdpContext {
 }
 
 pub async fn dispatch(req: &CdpRequest, ctx: &mut CdpContext) -> CdpResponse {
+    // headless_chrome (and older Puppeteer) wrap every CDP call inside
+    // Target.sendMessageToTarget. Unwrap and recurse BEFORE acquiring the
+    // V8 lock — the recursive dispatch will acquire it for the inner call,
+    // and tokio Mutex is not reentrant.
+    if req.method == "Target.sendMessageToTarget" {
+        return dispatch_send_message_to_target(req, ctx).await;
+    }
+
     // Issue #19: V8 fatal abort under concurrent CDP work.
     //
     // Every CDP handler below may end up calling into a per-Page `JsRuntime`
@@ -187,6 +195,63 @@ pub async fn dispatch(req: &CdpRequest, ctx: &mut CdpContext) -> CdpResponse {
     }
 }
 
+async fn dispatch_send_message_to_target(req: &CdpRequest, ctx: &mut CdpContext) -> CdpResponse {
+    let session_id = req
+        .params
+        .get("sessionId")
+        .and_then(|v| v.as_str())
+        .map(str::to_string);
+    let message = match req.params.get("message").and_then(|v| v.as_str()) {
+        Some(m) => m,
+        None => {
+            return CdpResponse::error(
+                req.id,
+                -32602,
+                "sendMessageToTarget requires a message string".into(),
+                req.session_id.clone(),
+            );
+        }
+    };
+
+    let inner: CdpRequest = match serde_json::from_str(message) {
+        Ok(r) => r,
+        Err(e) => {
+            return CdpResponse::error(
+                req.id,
+                -32700,
+                format!("sendMessageToTarget message is not a valid CDP request: {e}"),
+                req.session_id.clone(),
+            );
+        }
+    };
+
+    // Override the inner session with the one supplied by the wrapper so
+    // the inner dispatch routes against the right page. Boxing the future
+    // sidesteps the async-fn recursion limit.
+    let inner_with_session = CdpRequest {
+        id: inner.id,
+        method: inner.method.clone(),
+        params: inner.params,
+        session_id: session_id.clone().or(inner.session_id),
+    };
+    let inner_response = Box::pin(dispatch(&inner_with_session, ctx)).await;
+
+    // Re-emit the inner response as the legacy event headless_chrome (and
+    // older Puppeteer) listen for instead of correlating responses by id.
+    let inner_serialized = serde_json::to_string(&inner_response).unwrap_or_else(|_| "{}".into());
+    ctx.pending_events.push(CdpEvent {
+        method: "Target.receivedMessageFromTarget".to_string(),
+        params: json!({
+            "sessionId": session_id.clone().unwrap_or_default(),
+            "message": inner_serialized,
+            "targetId": session_id.clone().unwrap_or_default(),
+        }),
+        session_id: req.session_id.clone(),
+    });
+
+    CdpResponse::success(req.id, json!({}), req.session_id.clone())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -217,4 +282,60 @@ mod tests {
         assert_eq!(err.code, -32601);
         assert!(err.message.contains("Unknown domain"));
     }
+
+    #[tokio::test]
+    async fn send_message_to_target_unwraps_inner_call() {
+        let mut ctx = CdpContext::new();
+        let inner = json!({
+            "id": 42,
+            "method": "Browser.getVersion",
+            "params": {},
+        });
+        let outer = CdpRequest {
+            id: 99,
+            method: "Target.sendMessageToTarget".into(),
+            params: json!({
+                "sessionId": "sess-1",
+                "message": inner.to_string(),
+            }),
+            session_id: None,
+        };
+
+        let resp = dispatch(&outer, &mut ctx).await;
+        assert!(resp.error.is_none(), "wrapper must succeed: {:?}", resp.error);
+        assert_eq!(resp.id, 99);
+        assert_eq!(resp.result, Some(json!({})));
+
+        // headless_chrome reads the inner response from the
+        // receivedMessageFromTarget event, not from the wrapper response.
+        let evt = ctx
+            .pending_events
+            .iter()
+            .find(|e| e.method == "Target.receivedMessageFromTarget")
+            .expect("receivedMessageFromTarget event must be emitted");
+        assert_eq!(evt.params["sessionId"], "sess-1");
+        let inner_msg = evt.params["message"].as_str().expect("message is a string");
+        let parsed: serde_json::Value = serde_json::from_str(inner_msg).unwrap();
+        assert_eq!(parsed["id"], 42);
+        // Browser.getVersion returns a populated result object, not an error.
+        assert!(parsed.get("result").is_some(), "inner response carries result");
+        assert!(parsed.get("error").is_none(), "inner response is not an error");
+    }
+
+    #[tokio::test]
+    async fn send_message_to_target_rejects_invalid_message() {
+        let mut ctx = CdpContext::new();
+        let outer = CdpRequest {
+            id: 5,
+            method: "Target.sendMessageToTarget".into(),
+            params: json!({
+                "sessionId": "sess-1",
+                "message": "{not valid json",
+            }),
+            session_id: None,
+        };
+        let resp = dispatch(&outer, &mut ctx).await;
+        let err = resp.error.expect("malformed inner messages must error");
+        assert_eq!(err.code, -32700);
+    }
 }