fix: coerce append/set arguments to USVStrings

Completes the review follow-up: append() and set() now run both
arguments through the same USVString coercion as the rest of the
binding, instead of casting them to strings blindly. A
number/boolean/object argument coerces via toString; a Symbol (or a
throwing toString) raises a TypeError before anything is appended or
replaced.

Author: adrian-niculescu

test-app/app/src/main/assets/app/tests/testURLSearchParamsImpl.js

@@ -443,6 +443,26 @@ describe("Test URLSearchParams ", function () {
         expect(params.get("a")).toBe("1");
     });
 
+    it("Test URLSearchParams coerces non-string arguments in append and set", function(){
+        const params = new URLSearchParams();
+        params.append(1, 2);
+        expect(params.get("1")).toBe("2");
+        params.set(true, { toString: function(){ return "x"; } });
+        expect(params.get("true")).toBe("x");
+        params.append("a", null);
+        expect(params.get("a")).toBe("null");
+    });
+
+    it("Test URLSearchParams append and set throw when an argument is a Symbol", function(){
+        const params = new URLSearchParams("a=1");
+        expect(function(){ params.append(Symbol("x"), "v"); }).toThrow();
+        expect(function(){ params.append("k", Symbol("x")); }).toThrow();
+        expect(function(){ params.set(Symbol("x"), "v"); }).toThrow();
+        expect(function(){ params.set("k", Symbol("x")); }).toThrow();
+        // Nothing was appended or replaced by the failed calls.
+        expect(params.toString()).toBe("a=1");
+    });
+
     // --- Brand checks: iterators require a genuine receiver. ---
 
     it("Test URLSearchParams entries/keys/values throw on a foreign receiver", function(){

test-app/runtime/src/main/cpp/URLSearchParamsImpl.cpp

@@ -543,9 +543,16 @@ namespace tns {
         if (ptr == nullptr) {
             return;
         }
-        auto key = ArgConverter::ConvertToString(args[0].As<v8::String>());
-        auto value = ArgConverter::ConvertToString(args[1].As<v8::String>());
-        ptr->GetURLSearchParams()->append(key.c_str(), value.c_str());
+        // Both arguments are USVStrings (url.bs:3860); a Symbol or throwing
+        // toString leaves the pending exception and aborts.
+        auto context = args.GetIsolate()->GetCurrentContext();
+        std::string key;
+        std::string value;
+        if (!ValueToString(context, args[0], key) ||
+            !ValueToString(context, args[1], value)) {
+            return;
+        }
+        ptr->GetURLSearchParams()->append(key, value);
     }
 
     void URLSearchParamsImpl::Delete(const v8::FunctionCallbackInfo<v8::Value> &args) {
@@ -708,13 +715,16 @@ namespace tns {
         if (ptr == nullptr) {
             return;
         }
-        auto key = args[0].As<v8::String>();
-        auto value = args[1].As<v8::String>();
-
-        ptr->GetURLSearchParams()->set(
-                ArgConverter::ConvertToString(key),
-                ArgConverter::ConvertToString(value)
-        );
+        // Both arguments are USVStrings (url.bs:3865); a Symbol or throwing
+        // toString leaves the pending exception and aborts.
+        auto context = args.GetIsolate()->GetCurrentContext();
+        std::string key;
+        std::string value;
+        if (!ValueToString(context, args[0], key) ||
+            !ValueToString(context, args[1], value)) {
+            return;
+        }
+        ptr->GetURLSearchParams()->set(key, value);
     }
 
     void URLSearchParamsImpl::GetSize(v8::Local<v8::String> property,