[kinetics] Track undeclared third body usage

include/cantera/kinetics/Kinetics.h

@@ -1625,6 +1625,9 @@ protected:
     //! See skipUndeclaredThirdBodies()
     bool m_skipUndeclaredThirdBodies = false;
 
+    //! Flag indicating whether reactions include undeclared third bodies
+    bool m_hasUndeclaredThirdBodies = false;
+
     //! reference to Solution
     std::weak_ptr<Solution> m_root;
 };

src/kinetics/BulkKinetics.cpp

@@ -88,6 +88,8 @@ void BulkKinetics::addThirdBody(shared_ptr<Reaction> r)
             throw CanteraError("BulkKinetics::addThirdBody", "Found third-body"
                 " efficiency for undefined species '{}' while adding reaction '{}'",
                 name, r->equation());
+        } else {
+            m_hasUndeclaredThirdBodies = true;
         }
     }
     m_multi_concm.install(nReactions() - 1, efficiencies,

src/kinetics/Kinetics.cpp

@@ -643,6 +643,9 @@ AnyMap Kinetics::parameters()
         if (nReactions() == 0) {
             out["reactions"] = "none";
         }
+        if (m_hasUndeclaredThirdBodies) {
+            out["skip-undeclared-third-bodies"] = true;
+        }
     }
     return out;
 }