Bug 1823354 - Implement URL.canParse() r=emilio

Implemented URL.canParse() static function for checking if a URL can be
parsed (instead of having to try wrap the constructor).

Avoids using an ErrorResult/Throws as it is not specified, and for
performance (see spec issue from linked PR).

All WPT tests for it now pass.

Spec PR: whatwg/url#763
WPT tests: https://wpt.fyi/results/url/url-statics-canparse.any.html

Differential Revision: https://phabricator.services.mozilla.com/D179617

dom/url/URL.cpp

@@ -131,6 +131,34 @@ bool URL::IsValidURL(const GlobalObject& aGlobal, const nsAString& aURL,
   return URLWorker::IsValidURL(aGlobal, aURL, aRv);
 }
 
+bool URL::CanParse(const GlobalObject& aGlobal, const nsAString& aURL,
+                   const Optional<nsAString>& aBase) {
+  nsCOMPtr<nsIURI> baseUri;
+  if (aBase.WasPassed()) {
+    // Don't use NS_ConvertUTF16toUTF8 because that doesn't let us handle OOM.
+    nsAutoCString base;
+    if (!AppendUTF16toUTF8(aBase.Value(), base, fallible)) {
+      // Just return false with OOM errors as no ErrorResult.
+      return false;
+    }
+
+    nsresult rv = NS_NewURI(getter_AddRefs(baseUri), base);
+    if (NS_FAILED(rv)) {
+      // Invalid base URL, return false.
+      return false;
+    }
+  }
+
+  nsAutoCString urlStr;
+  if (!AppendUTF16toUTF8(aURL, urlStr, fallible)) {
+    // Just return false with OOM errors as no ErrorResult.
+    return false;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  return NS_SUCCEEDED(NS_NewURI(getter_AddRefs(uri), urlStr, nullptr, baseUri));
+}
+
 URLSearchParams* URL::SearchParams() {
   CreateSearchParamsIfNeeded();
   return mSearchParams;

dom/url/URL.h

@@ -69,6 +69,9 @@ class URL final : public URLSearchParamsObserver, public nsWrapperCache {
   static bool IsValidURL(const GlobalObject& aGlobal, const nsAString& aURL,
                          ErrorResult& aRv);
 
+  static bool CanParse(const GlobalObject& aGlobal, const nsAString& aURL,
+                       const Optional<nsAString>& aBase);
+
   void GetHref(nsAString& aHref) const;
 
   void SetHref(const nsAString& aHref, ErrorResult& aRv);

dom/webidl/URL.webidl

@@ -19,6 +19,8 @@ interface URL {
   [Throws]
   constructor(USVString url, optional USVString base);
 
+  static boolean canParse(USVString url, optional USVString base);
+
   [SetterThrows]
   stringifier attribute USVString href;
   readonly attribute USVString origin;