Merge pull request #81822 from nlupugla/nodepath-slice

Add `NodePath::slice` method

5 files changed, 97 insertions, 2 deletions

diff --git a/core/string/node_path.cpp b/core/string/node_path.cpp
index 32e4564c5e..8ae2efb787 100644
--- a/core/string/node_path.cpp
+++ b/core/string/node_path.cpp
@@ -92,6 +92,14 @@ StringName NodePath::get_subname(int p_idx) const {
 	return data->subpath[p_idx];
 }
 
+int NodePath::get_total_name_count() const {
+	if (!data) {
+		return 0;
+	}
+
+	return data->path.size() + data->subpath.size();
+}
+
 void NodePath::unref() {
 	if (data && data->refcount.unref()) {
 		memdelete(data);
@@ -229,6 +237,27 @@ StringName NodePath::get_concatenated_subnames() const {
 	return data->concatenated_subpath;
 }
 
+NodePath NodePath::slice(int p_begin, int p_end) const {
+	const int name_count = get_name_count();
+	const int total_count = get_total_name_count();
+
+	int begin = CLAMP(p_begin, -total_count, total_count);
+	if (begin < 0) {
+		begin += total_count;
+	}
+	int end = CLAMP(p_end, -total_count, total_count);
+	if (end < 0) {
+		end += total_count;
+	}
+	const int sub_begin = MAX(begin - name_count - 1, 0);
+	const int sub_end = MAX(end - name_count, 0);
+
+	const Vector<StringName> names = get_names().slice(begin, end);
+	const Vector<StringName> sub_names = get_subnames().slice(sub_begin, sub_end);
+	const bool absolute = is_absolute() && (begin == 0);
+	return NodePath(names, sub_names, absolute);
+}
+
 NodePath NodePath::rel_path_to(const NodePath &p_np) const {
 	ERR_FAIL_COND_V(!is_absolute(), NodePath());
 	ERR_FAIL_COND_V(!p_np.is_absolute(), NodePath());
@@ -331,7 +360,7 @@ NodePath NodePath::simplified() const {
 }
 
 NodePath::NodePath(const Vector<StringName> &p_path, bool p_absolute) {
-	if (p_path.size() == 0) {
+	if (p_path.size() == 0 && !p_absolute) {
 		return;
 	}
 
@@ -343,7 +372,7 @@ NodePath::NodePath(const Vector<StringName> &p_path, bool p_absolute) {
 }
 
 NodePath::NodePath(const Vector<StringName> &p_path, const Vector<StringName> &p_subpath, bool p_absolute) {
-	if (p_path.size() == 0 && p_subpath.size() == 0) {
+	if (p_path.size() == 0 && p_subpath.size() == 0 && !p_absolute) {
 		return;
 	}
 
diff --git a/core/string/node_path.h b/core/string/node_path.h
index 876d69924e..56799839d7 100644
--- a/core/string/node_path.h
+++ b/core/string/node_path.h
@@ -57,10 +57,12 @@ public:
 	StringName get_name(int p_idx) const;
 	int get_subname_count() const;
 	StringName get_subname(int p_idx) const;
+	int get_total_name_count() const;
 	Vector<StringName> get_names() const;
 	Vector<StringName> get_subnames() const;
 	StringName get_concatenated_names() const;
 	StringName get_concatenated_subnames() const;
+	NodePath slice(int p_begin, int p_end = INT_MAX) const;
 
 	NodePath rel_path_to(const NodePath &p_np) const;
 	NodePath get_as_property_path() const;
diff --git a/core/variant/variant_call.cpp b/core/variant/variant_call.cpp
index b551a7059e..503254d1d3 100644
--- a/core/variant/variant_call.cpp
+++ b/core/variant/variant_call.cpp
@@ -2033,6 +2033,7 @@ static void _register_variant_builtin_methods() {
 	bind_method(NodePath, get_subname, sarray("idx"), varray());
 	bind_method(NodePath, get_concatenated_names, sarray(), varray());
 	bind_method(NodePath, get_concatenated_subnames, sarray(), varray());
+	bind_method(NodePath, slice, sarray("begin", "end"), varray(INT_MAX));
 	bind_method(NodePath, get_as_property_path, sarray(), varray());
 	bind_method(NodePath, is_empty, sarray(), varray());
 
diff --git a/doc/classes/NodePath.xml b/doc/classes/NodePath.xml
index fa6f158b6e..6e0799e796 100644
--- a/doc/classes/NodePath.xml
+++ b/doc/classes/NodePath.xml
@@ -199,6 +199,16 @@
 				Returns [code]true[/code] if the node path has been constructed from an empty [String] ([code]""[/code]).
 			</description>
 		</method>
+		<method name="slice" qualifiers="const">
+			<return type="NodePath" />
+			<param index="0" name="begin" type="int" />
+			<param index="1" name="end" type="int" default="2147483647" />
+			<description>
+				Returns the slice of the [NodePath], from [param begin] (inclusive) to [param end] (exclusive), as a new [NodePath].
+				The absolute value of [param begin] and [param end] will be clamped to the sum of [method get_name_count] and [method get_subname_count], so the default value for [param end] makes it slice to the end of the [NodePath] by default (i.e. [code]path.slice(1)[/code] is a shorthand for [code]path.slice(1, path.get_name_count() + path.get_subname_count())[/code]).
+				If either [param begin] or [param end] are negative, they will be relative to the end of the [NodePath] (i.e. [code]path.slice(0, -2)[/code] is a shorthand for [code]path.slice(0, path.get_name_count() + path.get_subname_count() - 2)[/code]).
+			</description>
+		</method>
 	</methods>
 	<operators>
 		<operator name="operator !=">
diff --git a/tests/core/string/test_node_path.h b/tests/core/string/test_node_path.h
index 031a33c570..bdbc578e85 100644
--- a/tests/core/string/test_node_path.h
+++ b/tests/core/string/test_node_path.h
@@ -167,6 +167,59 @@ TEST_CASE("[NodePath] Empty path") {
 			node_path_empty.is_empty(),
 			"The node path should be considered empty.");
 }
+
+TEST_CASE("[NodePath] Slice") {
+	const NodePath node_path_relative = NodePath("Parent/Child:prop");
+	const NodePath node_path_absolute = NodePath("/root/Parent/Child:prop");
+	CHECK_MESSAGE(
+			node_path_relative.slice(0, 2) == NodePath("Parent/Child"),
+			"The slice lower bound should be inclusive and the slice upper bound should be exclusive.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(3) == NodePath(":prop"),
+			"Slicing on the length of the path should return the last entry.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(1, 3) == NodePath("Child:prop"),
+			"Slicing should include names and subnames.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(-1) == NodePath(":prop"),
+			"Slicing on -1 should return the last entry.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(0, -1) == NodePath("Parent/Child"),
+			"Slicing up to -1 should include the second-to-last entry.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(-2, -1) == NodePath("Child"),
+			"Slicing from negative to negative should treat lower bound as inclusive and upper bound as exclusive.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(0, 10) == NodePath("Parent/Child:prop"),
+			"Slicing past the length of the path should work like slicing up to the last entry.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(-10, 2) == NodePath("Parent/Child"),
+			"Slicing negatively past the length of the path should work like slicing from the first entry.");
+	CHECK_MESSAGE(
+			node_path_relative.slice(1, 1) == NodePath(""),
+			"Slicing with a lower bound equal to upper bound should return empty path.");
+
+	CHECK_MESSAGE(
+			node_path_absolute.slice(0, 2) == NodePath("/root/Parent"),
+			"Slice from beginning of an absolute path should be an absolute path.");
+	CHECK_MESSAGE(
+			node_path_absolute.slice(1, 4) == NodePath("Parent/Child:prop"),
+			"Slice of an absolute path that does not start at the beginning should be a relative path.");
+	CHECK_MESSAGE(
+			node_path_absolute.slice(3, 4) == NodePath(":prop"),
+			"Slice of an absolute path that does not start at the beginning should be a relative path.");
+
+	CHECK_MESSAGE(
+			NodePath("").slice(0, 1) == NodePath(""),
+			"Slice of an empty path should be an empty path.");
+	CHECK_MESSAGE(
+			NodePath("").slice(-1, 2) == NodePath(""),
+			"Slice of an empty path should be an empty path.");
+	CHECK_MESSAGE(
+			NodePath("/").slice(-1, 2) == NodePath("/"),
+			"Slice of an empty absolute path should be an empty absolute path.");
+}
+
 } // namespace TestNodePath
 
 #endif // TEST_NODE_PATH_H