Properly handle base URL argument in URL constructor (#33)

Plus, more proper error handling for invalid URLs. "More proper" because we should generate more helpful error messages, but this is an improvement for now.

Author: tschneidereit

CHANGELOG.md

@@ -1,3 +1,10 @@
+## 0.2.1 (2021-08-27)
+
+### Fixes
+
+- Properly support `base` argument in `URL` constructor
+  [#33](https://github.com/fastly/js-compute-runtime/pull/33)
+
 ## 0.2.0 (2021-08-24)
 
 ### Enhancements

c-dependencies/js-compute-runtime/js-compute-builtins.cpp

@@ -3777,7 +3777,7 @@ namespace URL {
       auto str = encode(cx, base_val);
       if (!str.data) return nullptr;
 
-      JSUrl* base = jsurl::new_jsurl(&str);
+      base = jsurl::new_jsurl(&str);
       if (!base) {
         JS_ReportErrorUTF8(cx, "URL constructor: %s is not a valid URL.", (char*)str.data);
         return nullptr;
@@ -3794,6 +3794,11 @@ namespace URL {
       url = jsurl::new_jsurl(&str);
     }
 
+    if (!url) {
+      JS_ReportErrorUTF8(cx, "URL constructor: %s is not a valid URL.", (char*)str.data);
+      return nullptr;
+    }
+
     JS::SetReservedSlot(self, Slots::Url, JS::PrivateValue(url));
 
     return self;