LibWeb: Accept array pairs in URLSearchParams constructor

Userland/Libraries/LibWeb/URL/URLSearchParams.cpp

@@ -66,24 +66,45 @@ Vector<QueryParam> url_decode(StringView input)
     return output;
 }
 
-DOM::ExceptionOr<NonnullRefPtr<URLSearchParams>> URLSearchParams::create_with_global_object(Bindings::WindowObject&, String const& init)
+DOM::ExceptionOr<NonnullRefPtr<URLSearchParams>> URLSearchParams::create_with_global_object(Bindings::WindowObject&, Variant<Vector<Vector<String>>, String> const& init)
 {
     // 1. If init is a string and starts with U+003F (?), then remove the first code point from init.
-    StringView stripped_init = init.substring_view(init.starts_with('?'));
+    // NOTE: We do this when we know that it's a string on step 3 of initialization.
+
     // 2. Initialize this with init.
 
     // URLSearchParams init from this point forward
 
-    // TODO
     // 1. If init is a sequence, then for each pair in init:
-    // a. If pair does not contain exactly two items, then throw a TypeError.
-    // b. Append a new name-value pair whose name is pair’s first item, and value is pair’s second item, to query’s list.
+    if (init.has<Vector<Vector<String>>>()) {
+        auto const& init_sequence = init.get<Vector<Vector<String>>>();
+
+        Vector<QueryParam> list;
+        list.ensure_capacity(init_sequence.size());
+
+        for (auto const& pair : init_sequence) {
+            // a. If pair does not contain exactly two items, then throw a TypeError.
+            if (pair.size() != 2)
+                return DOM::SimpleException { DOM::SimpleExceptionType::TypeError, String::formatted("Expected only 2 items in pair, got {}", pair.size()) };
+
+            // b. Append a new name-value pair whose name is pair’s first item, and value is pair’s second item, to query’s list.
+            list.append(QueryParam { .name = pair[0], .value = pair[1] });
+        }
+
+        return URLSearchParams::create(move(list));
+    }
 
     // TODO
     // 2. Otherwise, if init is a record, then for each name → value of init, append a new name-value pair whose name is name and value is value, to query’s list.
 
     // 3. Otherwise:
     // a. Assert: init is a string.
+    // NOTE: `get` performs `VERIFY(has<T>())`
+    auto const& init_string = init.get<String>();
+
+    // See NOTE at the start of this function.
+    StringView stripped_init = init_string.substring_view(init_string.starts_with('?'));
+
     // b. Set query’s list to the result of parsing init.
     return URLSearchParams::create(url_decode(stripped_init));
 }