fix(runtime): preserve URL state in subclasses

changelog.d/11090-url-subclass-state.md

@@ -0,0 +1,3 @@
+### Fixed
+
+- Preserve parsed URL state when constructing classes that extend `URL`, including subclasses with an implicit constructor and constructors that explicitly call `super(...)`. URL subclasses now retain their own prototype and fields while exposing the expected URL properties and `instanceof` behavior.

crates/perry-codegen/src/expr/instance_misc1.rs

@@ -122,6 +122,7 @@ pub(crate) fn builtin_parent_reserved_class_id(name: &str) -> Option<u32> {
         "BigInt64Array" => 0xFFFF0039,
         "BigUint64Array" => 0xFFFF003A,
         "Function" => 0xFFFF00F0,
+        "URL" => 0xFFFF0063,
         // #10556: `class Sub extends EventEmitter {}` — same shape as the
         // Array/Map/Set/Error builtins above. Without this edge,
         // `new Sub() instanceof EventEmitter` never reaches the class-chain
@@ -554,6 +555,7 @@ pub(crate) fn lower(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
                 "ReadableStream" => 0xFFFF0060u32,
                 "WritableStream" => 0xFFFF0061u32,
                 "TransformStream" => 0xFFFF0062u32,
+                "URL" => 0xFFFF0063u32,
                 // node:stream/web codec stream constructors are heap
                 // ObjectHeader instances with runtime-owned class IDs.
                 "TextEncoderStream" => 0x7FFFFF30u32,

crates/perry-codegen/src/expr/this_super_call.rs

@@ -130,11 +130,10 @@ pub(crate) fn bind_derived_this_after_super(ctx: &mut FnCtx<'_>) {
 /// SuperCall arms) that can appear as a class heritage. `super(...)` to these
 /// must NOT be routed through the runtime-value dispatch path
 /// (`js_fetch_or_value_super`), which would invoke e.g. `Map()` without `new`
-/// and throw "Constructor requires 'new'". Perry cannot yet give a subclass
-/// instance the built-in's internal slots, so `super()` is a best-effort no-op
-/// here — enough that `class M extends Map { constructor(){ super(); } }`
-/// constructs without throwing. Refs class/subclass/builtin-objects/*/
-/// super-must-be-called.
+/// and throw "Constructor requires 'new'". Dedicated arms below either install
+/// the built-in state on the provisional receiver or construct a branded value
+/// with the subclass as `newTarget`. Refs class/subclass/builtin-objects/*/
+/// super-must-be-called and #10639.
 pub(crate) fn is_other_builtin_constructor_name(name: &str) -> bool {
     matches!(
         name,
@@ -152,6 +151,7 @@ pub(crate) fn is_other_builtin_constructor_name(name: &str) -> bool {
             | "String"
             | "Date"
             | "RegExp"
+            | "URL"
             | "Promise"
             | "Function"
             | "BigInt"
@@ -1183,6 +1183,7 @@ pub(crate) fn lower(ctx: &mut FnCtx<'_>, expr: &Expr) -> Result<String> {
                             | "String"
                             | "Date"
                             | "RegExp"
+                            | "URL"
                             | "Function"
                             | "BigInt"
                             | "Symbol"

crates/perry-codegen/src/lower_call/new.rs

@@ -1445,6 +1445,7 @@ fn lower_new_impl_inner<'a>(
                         | "String"
                         | "Date"
                         | "RegExp"
+                        | "URL"
                         | "Function"
                         | "BigInt"
                         | "Symbol"

crates/perry-runtime/src/object/class_registry/construct.rs

@@ -1771,6 +1771,7 @@ pub unsafe extern "C" fn js_new_function_construct_with_new_target(
                 | "Number"
                 | "String"
                 | "RegExp"
+                | "URL"
                 | "Function"
         ) {
             let scope = crate::gc::RuntimeHandleScope::new();

crates/perry-runtime/src/object/instanceof.rs

@@ -17,6 +17,7 @@ const CLASS_ID_SUBTLE_CRYPTO: u32 = 0xFFFF00C1;
 const CLASS_ID_CRYPTO_KEY: u32 = 0xFFFF00C2;
 /// `value instanceof Function` reserved id (see `js_instanceof`).
 const CLASS_ID_FUNCTION: u32 = 0xFFFF00F0;
+const CLASS_ID_URL: u32 = 0xFFFF0063;
 
 mod dynamic_dispatch;
 mod static_dispatch;
@@ -212,6 +213,7 @@ pub(crate) fn global_builtin_constructor_class_id(name: &str) -> u32 {
         "BigInt" => 0xFFFF00D3,
         "Symbol" => 0xFFFF00D4,
         "Date" => 0xFFFF0020,
+        "URL" => CLASS_ID_URL,
         "Error" => crate::error::CLASS_ID_ERROR,
         "TypeError" => crate::error::CLASS_ID_TYPE_ERROR,
         "RangeError" => crate::error::CLASS_ID_RANGE_ERROR,

crates/perry-runtime/src/object/instanceof/static_dispatch.rs

@@ -108,6 +108,15 @@ pub extern "C" fn js_instanceof(value: f64, class_id: u32) -> f64 {
             false_val
         };
     }
+    if class_id == CLASS_ID_URL {
+        let addr = value_addr(value);
+        let branded = addr != 0 && crate::url::is_url_object_shape(addr as *mut ObjectHeader);
+        return if branded || recorded_prototype_instanceof_builtin(value, "URL") == Some(true) {
+            true_val
+        } else {
+            false_val
+        };
+    }
     // Keep in sync with perry-codegen/src/expr/instance_misc1.rs.
     let classic_stream_name = match class_id {
         0xFFFF0070 => Some("Stream"),

test-files/test_gap_10639_url_subclass.ts

@@ -0,0 +1,38 @@
+// #10639: a URL subclass must receive URL's internal state while preserving
+// its declared prototype and fields. Both the implicit derived constructor and
+// a written `super(input, base)` call used to leave hostname/pathname undefined.
+
+class ImplicitUrl extends URL {
+  kind = "implicit";
+}
+
+const implicit = new ImplicitUrl("child?q=1", "https://example.com/base/");
+console.log(
+  "implicit:",
+  implicit.hostname,
+  implicit.pathname,
+  implicit.search,
+  implicit.kind,
+  implicit instanceof ImplicitUrl,
+  implicit instanceof URL,
+);
+
+class ExplicitUrl extends URL {
+  kind: string;
+
+  constructor(input: string, base: string) {
+    super(input, base);
+    this.kind = "explicit";
+  }
+}
+
+const explicit = new ExplicitUrl("../next#hash", "https://perry.dev/a/b/");
+console.log(
+  "explicit:",
+  explicit.hostname,
+  explicit.pathname,
+  explicit.hash,
+  explicit.kind,
+  explicit instanceof ExplicitUrl,
+  explicit instanceof URL,
+);