[Net] Modularize multiplayer, expose MultiplayerAPI to extensions.

- RPC configurations are now dictionaries.
- Script.get_rpc_methods renamed to Script.get_rpc_config.
- Node.rpc[_id] and Callable.rpc now return an Error.
- Refactor MultiplayerAPI to allow extension.
- New MultiplayerAPI.rpc method with Array argument (for scripts).
- Move the default MultiplayerAPI implementation to a module.

2 files changed, 8 insertions, 5 deletions

diff --git a/core/variant/callable.cpp b/core/variant/callable.cpp
index f20ec4037a..8b9b5f41de 100644
--- a/core/variant/callable.cpp
+++ b/core/variant/callable.cpp
@@ -63,17 +63,19 @@ void Callable::call(const Variant **p_arguments, int p_argcount, Variant &r_retu
 	}
 }
 
-void Callable::rpc(int p_id, const Variant **p_arguments, int p_argcount, CallError &r_call_error) const {
+Error Callable::rpc(int p_id, const Variant **p_arguments, int p_argcount, CallError &r_call_error) const {
 	if (is_null()) {
 		r_call_error.error = CallError::CALL_ERROR_INSTANCE_IS_NULL;
 		r_call_error.argument = 0;
 		r_call_error.expected = 0;
+		return ERR_UNCONFIGURED;
 	} else if (!is_custom()) {
 		r_call_error.error = CallError::CALL_ERROR_INVALID_METHOD;
 		r_call_error.argument = 0;
 		r_call_error.expected = 0;
+		return ERR_UNCONFIGURED;
 	} else {
-		custom->rpc(p_id, p_arguments, p_argcount, r_call_error);
+		return custom->rpc(p_id, p_arguments, p_argcount, r_call_error);
 	}
 }
 
@@ -316,10 +318,11 @@ StringName CallableCustom::get_method() const {
 	ERR_FAIL_V_MSG(StringName(), vformat("Can't get method on CallableCustom \"%s\".", get_as_text()));
 }
 
-void CallableCustom::rpc(int p_peer_id, const Variant **p_arguments, int p_argcount, Callable::CallError &r_call_error) const {
+Error CallableCustom::rpc(int p_peer_id, const Variant **p_arguments, int p_argcount, Callable::CallError &r_call_error) const {
 	r_call_error.error = Callable::CallError::CALL_ERROR_INVALID_METHOD;
 	r_call_error.argument = 0;
 	r_call_error.expected = 0;
+	return ERR_UNCONFIGURED;
 }
 
 const Callable *CallableCustom::get_base_comparator() const {
diff --git a/core/variant/callable.h b/core/variant/callable.h
index bbcf5427ba..954365d010 100644
--- a/core/variant/callable.h
+++ b/core/variant/callable.h
@@ -71,7 +71,7 @@ public:
 	void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, CallError &r_call_error) const;
 	void call_deferred(const Variant **p_arguments, int p_argcount) const;
 
-	void rpc(int p_id, const Variant **p_arguments, int p_argcount, CallError &r_call_error) const;
+	Error rpc(int p_id, const Variant **p_arguments, int p_argcount, CallError &r_call_error) const;
 
 	_FORCE_INLINE_ bool is_null() const {
 		return method == StringName() && object == 0;
@@ -129,7 +129,7 @@ public:
 	virtual StringName get_method() const;
 	virtual ObjectID get_object() const = 0; //must always be able to provide an object
 	virtual void call(const Variant **p_arguments, int p_argcount, Variant &r_return_value, Callable::CallError &r_call_error) const = 0;
-	virtual void rpc(int p_peer_id, const Variant **p_arguments, int p_argcount, Callable::CallError &r_call_error) const;
+	virtual Error rpc(int p_peer_id, const Variant **p_arguments, int p_argcount, Callable::CallError &r_call_error) const;
 	virtual const Callable *get_base_comparator() const;
 
 	CallableCustom();