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/3d/navigation_region_3d.cpp b/scene/3d/navigation_region_3d.cpp
index 520bf0a1aa..86b78f847e 100644
--- a/scene/3d/navigation_region_3d.cpp
+++ b/scene/3d/navigation_region_3d.cpp
@@ -320,6 +320,25 @@ void NavigationRegion3D::_bind_methods() {
 	ADD_SIGNAL(MethodInfo("bake_finished"));
 }
 
+#ifndef DISABLE_DEPRECATED
+// Compatibility with earlier 4.0 betas.
+bool NavigationRegion3D::_set(const StringName &p_name, const Variant &p_value) {
+	if (p_name == "navmesh") {
+		set_navigation_mesh(p_value);
+		return true;
+	}
+	return false;
+}
+
+bool NavigationRegion3D::_get(const StringName &p_name, Variant &r_ret) const {
+	if (p_name == "navmesh") {
+		r_ret = get_navigation_mesh();
+		return true;
+	}
+	return false;
+}
+#endif // DISABLE_DEPRECATED
+
 void NavigationRegion3D::_navigation_changed() {
 	update_gizmos();
 	update_configuration_warnings();
diff --git a/scene/3d/navigation_region_3d.h b/scene/3d/navigation_region_3d.h
index 7dcfa9cfa4..811c0885a1 100644
--- a/scene/3d/navigation_region_3d.h
+++ b/scene/3d/navigation_region_3d.h
@@ -64,6 +64,11 @@ 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:
 	void set_enabled(bool p_enabled);
 	bool is_enabled() const;