AK: Provide a few mutable JSON object/array accessors

We have mutable accessors on the JsonValue class already. This will be
needed for interaction with Firefox's DevTools, where we will want to
mutate the serialized DOM tree we receive from WebContent.

AK/JsonArray.h

@@ -80,6 +80,13 @@ public:
 
     [[nodiscard]] ByteString to_byte_string() const { return serialized<StringBuilder>(); }
 
+    template<typename Callback>
+    void for_each(Callback callback)
+    {
+        for (auto& value : m_values)
+            callback(value);
+    }
+
     template<typename Callback>
     void for_each(Callback callback) const
     {
@@ -87,6 +94,14 @@ public:
             callback(value);
     }
 
+    template<FallibleFunction<JsonValue&> Callback>
+    ErrorOr<void, CallbackErrorType<Callback>> try_for_each(Callback&& callback)
+    {
+        for (auto& value : m_values)
+            TRY(callback(value));
+        return {};
+    }
+
     template<FallibleFunction<JsonValue const&> Callback>
     ErrorOr<void, CallbackErrorType<Callback>> try_for_each(Callback&& callback) const
     {
@@ -95,6 +110,7 @@ public:
         return {};
     }
 
+    [[nodiscard]] Vector<JsonValue>& values() { return m_values; }
     [[nodiscard]] Vector<JsonValue> const& values() const { return m_values; }
 
     void ensure_capacity(size_t capacity) { m_values.ensure_capacity(capacity); }

AK/JsonObject.cpp

@@ -47,6 +47,14 @@ bool JsonObject::is_empty() const
     return m_members.is_empty();
 }
 
+Optional<JsonValue&> JsonObject::get(StringView key)
+{
+    auto it = m_members.find(key);
+    if (it == m_members.end())
+        return {};
+    return it->value;
+}
+
 Optional<JsonValue const&> JsonObject::get(StringView key) const
 {
     auto it = m_members.find(key);
@@ -116,6 +124,14 @@ Optional<ByteString> JsonObject::get_byte_string(StringView key) const
     return {};
 }
 
+Optional<JsonObject&> JsonObject::get_object(StringView key)
+{
+    auto maybe_value = get(key);
+    if (maybe_value.has_value() && maybe_value->is_object())
+        return maybe_value->as_object();
+    return {};
+}
+
 Optional<JsonObject const&> JsonObject::get_object(StringView key) const
 {
     auto maybe_value = get(key);
@@ -124,6 +140,14 @@ Optional<JsonObject const&> JsonObject::get_object(StringView key) const
     return {};
 }
 
+Optional<JsonArray&> JsonObject::get_array(StringView key)
+{
+    auto maybe_value = get(key);
+    if (maybe_value.has_value() && maybe_value->is_array())
+        return maybe_value->as_array();
+    return {};
+}
+
 Optional<JsonArray const&> JsonObject::get_array(StringView key) const
 {
     auto maybe_value = get(key);

AK/JsonObject.h

@@ -52,6 +52,7 @@ public:
     [[nodiscard]] bool has_array(StringView key) const;
     [[nodiscard]] bool has_object(StringView key) const;
 
+    Optional<JsonValue&> get(StringView key);
     Optional<JsonValue const&> get(StringView key) const;
 
     template<Integral T>
@@ -76,7 +77,10 @@ public:
 
     Optional<ByteString> get_byte_string(StringView key) const;
 
+    Optional<JsonObject&> get_object(StringView key);
     Optional<JsonObject const&> get_object(StringView key) const;
+
+    Optional<JsonArray&> get_array(StringView key);
     Optional<JsonArray const&> get_array(StringView key) const;
 
     Optional<double> get_double_with_precision_loss(StringView key) const;