Bring back error handling for tee()

src/readable/mod.rs

@@ -259,10 +259,11 @@ impl ReadableStream {
     /// If the stream is already locked to a reader, then this returns an error
     /// along with the original `ReadableStream`.
     pub fn try_tee(self) -> Result<(ReadableStream, ReadableStream), (js_sys::Error, Self)> {
-        if self.is_locked() {
-            return Err((js_sys::Error::new("Already locked"), self));
-        }
-        let branches = self.as_raw().tee();
+        let branches = self
+            .as_raw()
+            .unchecked_ref::<sys::ReadableStreamExt>()
+            .try_tee()
+            .map_err(|err| (err, self))?;
         debug_assert_eq!(branches.length(), 2);
         let (left, right) = (branches.get(0), branches.get(1));
         Ok((

src/readable/sys.rs

@@ -1,7 +1,7 @@
 //! Raw bindings to JavaScript objects used
 //! by a [`ReadableStream`](https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream).
 //! These are re-exported from [web-sys](https://docs.rs/web-sys/0.3.64/web_sys/struct.ReadableStream.html).
-use js_sys::{Error, Object, Uint8Array};
+use js_sys::{Array, Error, Object, Uint8Array};
 use wasm_bindgen::prelude::*;
 pub use web_sys::ReadableByteStreamController;
 // Re-export from web-sys
@@ -27,6 +27,9 @@ extern "C" {
         this: &ReadableStreamExt,
         options: &ReadableStreamGetReaderOptions,
     ) -> Result<Object, Error>;
+
+    #[wasm_bindgen(method, catch, js_name = tee)]
+    pub(crate) fn try_tee(this: &ReadableStreamExt) -> Result<Array, Error>;
 }
 
 #[wasm_bindgen]