From 203d3be200c9b607e5eaba82d9a267813a6700cd Mon Sep 17 00:00:00 2001
From: A Thousand Ships <96648715+AThousandShips@users.noreply.github.com>
Date: Thu, 18 Jan 2024 17:20:56 +0100
Subject: [PATCH] [Core] Add way to check if a signal has any connections

Added to `Object` and `Signal`
---
 core/object/object.cpp        | 19 +++++++++++++++++++
 core/object/object.h          |  1 +
 core/variant/callable.cpp     |  7 +++++++
 core/variant/callable.h       |  1 +
 core/variant/variant_call.cpp |  1 +
 doc/classes/Object.xml        |  8 ++++++++
 doc/classes/Signal.xml        |  6 ++++++
 scene/main/node.cpp           |  5 +++++
 scene/main/node.h             |  1 +
 9 files changed, 49 insertions(+)

diff --git a/core/object/object.cpp b/core/object/object.cpp
index 2d9d468d388..b3a4ec6e2ed 100644
--- a/core/object/object.cpp
+++ b/core/object/object.cpp
@@ -1457,6 +1457,24 @@ bool Object::is_connected(const StringName &p_signal, const Callable &p_callable
 	return s->slot_map.has(*p_callable.get_base_comparator());
 }
 
+bool Object::has_connections(const StringName &p_signal) const {
+	const SignalData *s = signal_map.getptr(p_signal);
+	if (!s) {
+		bool signal_is_valid = ClassDB::has_signal(get_class_name(), p_signal);
+		if (signal_is_valid) {
+			return false;
+		}
+
+		if (!script.is_null() && Ref<Script>(script)->has_script_signal(p_signal)) {
+			return false;
+		}
+
+		ERR_FAIL_V_MSG(false, "Nonexistent signal: " + p_signal + ".");
+	}
+
+	return !s->slot_map.is_empty();
+}
+
 void Object::disconnect(const StringName &p_signal, const Callable &p_callable) {
 	_disconnect(p_signal, p_callable);
 }
@@ -1697,6 +1715,7 @@ void Object::_bind_methods() {
 	ClassDB::bind_method(D_METHOD("connect", "signal", "callable", "flags"), &Object::connect, DEFVAL(0));
 	ClassDB::bind_method(D_METHOD("disconnect", "signal", "callable"), &Object::disconnect);
 	ClassDB::bind_method(D_METHOD("is_connected", "signal", "callable"), &Object::is_connected);
+	ClassDB::bind_method(D_METHOD("has_connections", "signal"), &Object::has_connections);
 
 	ClassDB::bind_method(D_METHOD("set_block_signals", "enable"), &Object::set_block_signals);
 	ClassDB::bind_method(D_METHOD("is_blocking_signals"), &Object::is_blocking_signals);
diff --git a/core/object/object.h b/core/object/object.h
index 1274247d716..763e2974b9d 100644
--- a/core/object/object.h
+++ b/core/object/object.h
@@ -932,6 +932,7 @@ public:
 	MTVIRTUAL Error connect(const StringName &p_signal, const Callable &p_callable, uint32_t p_flags = 0);
 	MTVIRTUAL void disconnect(const StringName &p_signal, const Callable &p_callable);
 	MTVIRTUAL bool is_connected(const StringName &p_signal, const Callable &p_callable) const;
+	MTVIRTUAL bool has_connections(const StringName &p_signal) const;
 
 	template <typename... VarArgs>
 	void call_deferred(const StringName &p_name, VarArgs... p_args) {
diff --git a/core/variant/callable.cpp b/core/variant/callable.cpp
index 9dff5c1e910..bb2d0313f66 100644
--- a/core/variant/callable.cpp
+++ b/core/variant/callable.cpp
@@ -545,6 +545,13 @@ bool Signal::is_connected(const Callable &p_callable) const {
 	return obj->is_connected(name, p_callable);
 }
 
+bool Signal::has_connections() const {
+	Object *obj = get_object();
+	ERR_FAIL_NULL_V(obj, false);
+
+	return obj->has_connections(name);
+}
+
 Array Signal::get_connections() const {
 	Object *obj = get_object();
 	if (!obj) {
diff --git a/core/variant/callable.h b/core/variant/callable.h
index 63757d9d6e4..e3c940a0e59 100644
--- a/core/variant/callable.h
+++ b/core/variant/callable.h
@@ -192,6 +192,7 @@ public:
 	Error connect(const Callable &p_callable, uint32_t p_flags = 0);
 	void disconnect(const Callable &p_callable);
 	bool is_connected(const Callable &p_callable) const;
+	bool has_connections() const;
 
 	Array get_connections() const;
 	Signal(const Object *p_object, const StringName &p_name);
diff --git a/core/variant/variant_call.cpp b/core/variant/variant_call.cpp
index 178c0bc4eca..63fb5e8d943 100644
--- a/core/variant/variant_call.cpp
+++ b/core/variant/variant_call.cpp
@@ -2121,6 +2121,7 @@ static void _register_variant_builtin_methods_misc() {
 	bind_method(Signal, disconnect, sarray("callable"), varray());
 	bind_method(Signal, is_connected, sarray("callable"), varray());
 	bind_method(Signal, get_connections, sarray(), varray());
+	bind_method(Signal, has_connections, sarray(), varray());
 
 	bind_custom(Signal, emit, _VariantCall::func_Signal_emit, false, Variant);
 
diff --git a/doc/classes/Object.xml b/doc/classes/Object.xml
index d0d0876108e..2767a11e806 100644
--- a/doc/classes/Object.xml
+++ b/doc/classes/Object.xml
@@ -824,6 +824,14 @@
 				Returns the name of the translation domain used by [method tr] and [method tr_n]. See also [TranslationServer].
 			</description>
 		</method>
+		<method name="has_connections" qualifiers="const">
+			<return type="bool" />
+			<param index="0" name="signal" type="StringName" />
+			<description>
+				Returns [code]true[/code] if any connection exists on the given [param signal] name.
+				[b]Note:[/b] In C#, [param signal] must be in snake_case when referring to built-in Godot methods. Prefer using the names exposed in the [code]SignalName[/code] class to avoid allocating a new [StringName] on each call.
+			</description>
+		</method>
 		<method name="has_meta" qualifiers="const">
 			<return type="bool" />
 			<param index="0" name="name" type="StringName" />
diff --git a/doc/classes/Signal.xml b/doc/classes/Signal.xml
index 7d6ff1e9b0c..65168d69806 100644
--- a/doc/classes/Signal.xml
+++ b/doc/classes/Signal.xml
@@ -109,6 +109,12 @@
 				Returns the ID of the object emitting this signal (see [method Object.get_instance_id]).
 			</description>
 		</method>
+		<method name="has_connections" qualifiers="const">
+			<return type="bool" />
+			<description>
+				Returns [code]true[/code] if any [Callable] is connected to this signal.
+			</description>
+		</method>
 		<method name="is_connected" qualifiers="const">
 			<return type="bool" />
 			<param index="0" name="callable" type="Callable" />
diff --git a/scene/main/node.cpp b/scene/main/node.cpp
index eb3448e1a2a..d921cc5b676 100644
--- a/scene/main/node.cpp
+++ b/scene/main/node.cpp
@@ -4019,4 +4019,9 @@ bool Node::is_connected(const StringName &p_signal, const Callable &p_callable)
 	return Object::is_connected(p_signal, p_callable);
 }
 
+bool Node::has_connections(const StringName &p_signal) const {
+	ERR_THREAD_GUARD_V(false);
+	return Object::has_connections(p_signal);
+}
+
 #endif
diff --git a/scene/main/node.h b/scene/main/node.h
index 4560ed085c1..298cbc7e595 100644
--- a/scene/main/node.h
+++ b/scene/main/node.h
@@ -797,6 +797,7 @@ public:
 	virtual Error connect(const StringName &p_signal, const Callable &p_callable, uint32_t p_flags = 0) override;
 	virtual void disconnect(const StringName &p_signal, const Callable &p_callable) override;
 	virtual bool is_connected(const StringName &p_signal, const Callable &p_callable) const override;
+	virtual bool has_connections(const StringName &p_signal) const override;
 #endif
 	Node();
 	~Node();