AK: Make HashMap::get(Key) return an Optional<Value>.

This allows HashMap::get() to be used for value types that cannot be default
constructed (e.g NonnullOwnPtr.)

AK/HashMap.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <AK/HashTable.h>
+#include <AK/Optional.h>
 #include <AK/StdLibExtras.h>
 #include <AK/Vector.h>
 #include <AK/kstdio.h>
@@ -51,21 +52,27 @@ public:
 
     IteratorType begin() { return m_table.begin(); }
     IteratorType end() { return m_table.end(); }
-    IteratorType find(const K& key) { return m_table.find(KeyTraits::hash(key), [&](auto& entry) { return KeyTraits::equals(key, entry.key); }); }
+    IteratorType find(const K& key)
+    {
+        return m_table.find(KeyTraits::hash(key), [&](auto& entry) { return KeyTraits::equals(key, entry.key); });
+    }
 
     ConstIteratorType begin() const { return m_table.begin(); }
     ConstIteratorType end() const { return m_table.end(); }
-    ConstIteratorType find(const K& key) const { return m_table.find(KeyTraits::hash(key), [&](auto& entry) { return KeyTraits::equals(key, entry.key); }); }
+    ConstIteratorType find(const K& key) const
+    {
+        return m_table.find(KeyTraits::hash(key), [&](auto& entry) { return KeyTraits::equals(key, entry.key); });
+    }
 
     void ensure_capacity(int capacity) { m_table.ensure_capacity(capacity); }
 
     void dump() const { m_table.dump(); }
 
-    V get(const K& key) const
+    Optional<V> get(const K& key) const
     {
         auto it = find(key);
         if (it == end())
-            return V();
+            return {};
         return (*it).value;
     }
 

AK/Optional.h

@@ -103,7 +103,9 @@ public:
         return fallback;
     }
 
+    operator bool() const { return has_value(); }
+
 private:
-    char m_storage[sizeof(T)] __attribute__((aligned(sizeof(T))));
+    char m_storage[sizeof(T)];
     bool m_has_value { false };
 };

Applications/Terminal/main.cpp

@@ -184,7 +184,8 @@ int main(int argc, char** argv)
         font_menu->add_action(GAction::create(font_name, [&terminal, &config](const GAction& action) {
             terminal.set_font(GFontDatabase::the().get_by_name(action.text()));
             auto metadata = GFontDatabase::the().get_metadata_by_name(action.text());
-            config->write_entry("Text", "Font", metadata.path);
+            ASSERT(metadata.has_value());
+            config->write_entry("Text", "Font", metadata.value().path);
             config->sync();
             terminal.force_repaint();
         }));

DevTools/VisualBuilder/VBForm.cpp

@@ -93,7 +93,7 @@ VBWidget* VBForm::widget_at(const Point& position)
     auto* gwidget = child_at(position);
     if (!gwidget)
         return nullptr;
-    return m_gwidget_map.get(gwidget);
+    return m_gwidget_map.get(gwidget).value_or(nullptr);
 }
 
 void VBForm::grabber_mousedown_event(GMouseEvent& event, Direction grabber)

Kernel/KParams.cpp

@@ -29,7 +29,7 @@ KParams::KParams(const String& cmdline)
 
 String KParams::get(const String& key) const
 {
-    return m_params.get(key);
+    return m_params.get(key).value_or({});
 }
 
 bool KParams::has(const String& key) const

Libraries/LibCore/CArgsParser.cpp

@@ -10,7 +10,7 @@ bool CArgsParserResult::is_present(const String& arg_name) const
 
 String CArgsParserResult::get(const String& arg_name) const
 {
-    return m_args.get(arg_name);
+    return m_args.get(arg_name).value_or({});
 }
 
 const Vector<String>& CArgsParserResult::get_single_values() const

Libraries/LibCore/CHttpJob.cpp

@@ -92,7 +92,7 @@ void CHttpJob::on_socket_connected()
         buffer.append(payload.pointer(), payload.size());
 
         bool ok;
-        if (buffer.size() >= m_headers.get("Content-Length").to_int(ok) && ok) {
+        if (buffer.size() >= m_headers.get("Content-Length").value_or("0").to_int(ok) && ok) {
             m_state = State::Finished;
             break;
         }

Libraries/LibGUI/GEventLoop.cpp

@@ -266,7 +266,7 @@ void GWindowServerConnection::postprocess_bundles(Vector<IncomingMessageBundle>&
         }
         switch (event.type) {
         case WSAPI_ServerMessage::Type::Paint:
-            if (Size(event.paint.window_size) != latest_paint_size_for_window_id.get(event.window_id)) {
+            if (Size(event.paint.window_size) != latest_paint_size_for_window_id.get(event.window_id).value_or({})) {
                 ++coalesced_paints;
                 break;
             }
@@ -295,7 +295,7 @@ void GWindowServerConnection::postprocess_bundles(Vector<IncomingMessageBundle>&
             handle_window_entered_or_left_event(event, *window);
             break;
         case WSAPI_ServerMessage::Type::WindowResized:
-            if (Size(event.window.rect.size) != latest_size_for_window_id.get(event.window_id)) {
+            if (Size(event.window.rect.size) != latest_size_for_window_id.get(event.window_id).value_or({})) {
                 ++coalesced_resizes;
                 break;
             }

Libraries/LibGUI/GFontDatabase.h

@@ -20,10 +20,10 @@ public:
     void for_each_font(Function<void(const StringView&)>);
     void for_each_fixed_width_font(Function<void(const StringView&)>);
 
-    Metadata get_metadata_by_name(const StringView& name) const
+    Optional<Metadata> get_metadata_by_name(const StringView& name) const
     {
         return m_name_to_metadata.get(name);
-    };
+    }
 
 private:
     GFontDatabase();

Servers/LookupServer/main.cpp

@@ -157,9 +157,9 @@ int main(int argc, char** argv)
         for (auto& key : dns_custom_hostnames.keys()) {
             dbgprintf("Known hostname: '%s'\n", key.characters());
         }
-        if (dns_custom_hostnames.contains(hostname)) {
-            responses.append(dns_custom_hostnames.get(hostname));
-            dbgprintf("LookupServer: Found preconfigured host (from /etc/hosts): %s\n", responses[0].characters());
+        if (auto known_host = dns_custom_hostnames.get(hostname)) {
+            responses.append(known_host.value());
+            dbg() << "LookupServer: Found preconfigured host (from /etc/hosts): " << known_host.value();
         } else if (!hostname.is_empty()) {
             bool did_timeout;
             int retries = 3;