Migrate Web Transport (#2324)

Co-authored-by: saschanaz <saschanaz@users.noreply.github.com>

Author: Bashamega

inputfiles/overridingTypes.jsonc

@@ -453,33 +453,6 @@
                 },
                 "overrideIndexSignatures": []
             },
-            "WebTransport": {
-                "methods": {
-                    "method": {
-                        "createUnidirectionalStream": {
-                            "signature": {
-                                "0": {
-                                    "subtype": {
-                                        "type": "WritableStream"
-                                    }
-                                }
-                            }
-                        }
-                    }
-                }
-            },
-            "WebTransportBidirectionalStream": {
-                "properties": {
-                    "property": {
-                        "readable": {
-                            "type": "ReadableStream"
-                        },
-                        "writable": {
-                            "type": "WritableStream"
-                        }
-                    }
-                }
-            },
             "Document": {
                 "methods": {
                     "method": {
@@ -1695,19 +1668,6 @@
                     ]
                 }
             },
-            "WebTransportDatagramDuplexStream": {
-                "properties": {
-                    "property": {
-                        // https://github.com/w3c/webtransport/pull/638 removed this but browsers still has this
-                        "writable": {
-                            "name": "writable",
-                            "type": "WritableStream",
-                            "readonly": true,
-                            "mdnUrl": "https://developer.mozilla.org/docs/Web/API/WebTransportDatagramDuplexStream/writable"
-                        }
-                    }
-                }
-            },
             "HTMLTableRowElement": {
                 "properties": {
                     "property": {

inputfiles/patches/webtransport.kdl

@@ -11,3 +11,23 @@ removals {
     member waitUntilAvailable // No implementation as of 2025-12.
   }
 }
+
+interface WebTransport {
+  // Only Gecko implements the return type as SendStream as of 2025-12
+  method createUnidirectionalStream signatureIndex=0 {
+    type {
+      type WritableStream
+    }
+  }
+}
+
+interface WebTransportBidirectionalStream {
+  // Only Gecko implements readable/writable as Receive/SendStream as of 2025-12
+  property readable type=ReadableStream
+  property writable type=WritableStream
+}
+
+interface WebTransportDatagramDuplexStream {
+  // https://github.com/w3c/webtransport/pull/638 removed this but browsers still have this
+  property writable type=WritableStream readonly=#true mdnUrl="https://developer.mozilla.org/docs/Web/API/WebTransportDatagramDuplexStream/writable"
+}

src/build/patches.ts

@@ -291,6 +291,7 @@ function handleProperty(child: Node): DeepPartial<Property> {
     ...handleTyped(typeNodes, child.properties?.type),
     ...optionalMember("readonly", "boolean", child.properties?.readonly),
     ...optionalMember("deprecated", "string", child.properties?.deprecated),
+    ...optionalMember("mdnUrl", "string", child.properties?.mdnUrl),
   };
 }