Skip friends outside of included scope

src/uml/class_diagram_visitor.h

@@ -215,8 +215,15 @@ static enum CXChildVisitResult friend_class_visitor(
     enum CXChildVisitResult ret = CXChildVisit_Break;
     switch (cursor.kind()) {
         case CXCursor_TypeRef: {
+            if (!ctx->ctx->config.should_include(
+                    cursor.referenced().fully_qualified())) {
+                ret = CXChildVisit_Continue;
+                break;
+            }
+
             spdlog::info("Adding friend declaration: {}, {}", cursor,
                 cursor.referenced());
+
             class_relationship r;
             r.type = relationship_t::kFriendship;
             r.label = "<<friend>>";

tests/t00011/t00011.cc

@@ -1,3 +1,8 @@
+namespace external {
+class C {
+};
+}
+
 namespace clanguml {
 namespace t00011 {
 
@@ -7,6 +12,7 @@ class A {
 private:
     void foo() {}
     friend class B;
+    friend class external::C;
 };
 
 class B {