LibWeb/IDB: Implement is_valid_key_path

Author: https://github.com/stelar7
Commit: https://github.com/LadybirdBrowser/ladybird/commit/0979a154fdd
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4077
Reviewed-by: https://github.com/AtkinsSJ
Reviewed-by: https://github.com/gmta ✅

Libraries/LibWeb/IndexedDB/Internal/Algorithms.cpp

@@ -589,4 +589,36 @@ JS::Value convert_a_key_to_a_value(JS::Realm& realm, GC::Ref<Key> key)
     VERIFY_NOT_REACHED();
 }
 
+// https://w3c.github.io/IndexedDB/#valid-key-path
+bool is_valid_key_path(KeyPath const& path)
+{
+    // A valid key path is one of:
+    return path.visit(
+        [](String const& value) -> bool {
+            // * An empty string.
+            if (value.is_empty())
+                return true;
+
+            // FIXME: * An identifier, which is a string matching the IdentifierName production from the ECMAScript Language Specification [ECMA-262].
+            return true;
+
+            // FIXME: * A string consisting of two or more identifiers separated by periods (U+002E FULL STOP).
+            return true;
+
+            return false;
+        },
+        [](Vector<String> const& values) -> bool {
+            // * A non-empty list containing only strings conforming to the above requirements.
+            if (values.is_empty())
+                return false;
+
+            for (auto const& value : values) {
+                if (!is_valid_key_path(value))
+                    return false;
+            }
+
+            return true;
+        });
+}
+
 }