Fix typo and ensure backwards compatibility for changed property names

Changes to the name of the `navmesh` and `navpoly` properties on
`NavigationRegion` caused navigation data to be lost on load.
This PR creates uses `_set`/`_get` to handle compatibility with the
older names on load, preserving the data.

Also fixes a typo on `get_vertices_per_polygon` in `NavigationMesh`,
and renames the property to remove the `polygon_` prefix which doesn't
match the setter/getter.

Co-authored-by: Rémi Verschelde <rverschelde@gmail.com>

2 files changed, 24 insertions, 0 deletions

diff --git a/scene/2d/navigation_region_2d.cpp b/scene/2d/navigation_region_2d.cpp
index e030628110..675ef7c780 100644
--- a/scene/2d/navigation_region_2d.cpp
+++ b/scene/2d/navigation_region_2d.cpp
@@ -309,6 +309,25 @@ void NavigationRegion2D::_bind_methods() {
 	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "travel_cost"), "set_travel_cost", "get_travel_cost");
 }
 
+#ifndef DISABLE_DEPRECATED
+// Compatibility with earlier 4.0 betas.
+bool NavigationRegion2D::_set(const StringName &p_name, const Variant &p_value) {
+	if (p_name == "navpoly") {
+		set_navigation_polygon(p_value);
+		return true;
+	}
+	return false;
+}
+
+bool NavigationRegion2D::_get(const StringName &p_name, Variant &r_ret) const {
+	if (p_name == "navpoly") {
+		r_ret = get_navigation_polygon();
+		return true;
+	}
+	return false;
+}
+#endif // DISABLE_DEPRECATED
+
 NavigationRegion2D::NavigationRegion2D() {
 	set_notify_transform(true);
 
diff --git a/scene/2d/navigation_region_2d.h b/scene/2d/navigation_region_2d.h
index 216e6088bc..45029fd95f 100644
--- a/scene/2d/navigation_region_2d.h
+++ b/scene/2d/navigation_region_2d.h
@@ -50,6 +50,11 @@ protected:
 	void _notification(int p_what);
 	static void _bind_methods();
 
+#ifndef DISABLE_DEPRECATED
+	bool _set(const StringName &p_name, const Variant &p_value);
+	bool _get(const StringName &p_name, Variant &r_ret) const;
+#endif // DISABLE_DEPRECATED
+
 public:
 #ifdef TOOLS_ENABLED
 	virtual Rect2 _edit_get_rect() const override;