feat: mark variables introduced by AP transforms with metadata

Author: AayushSabharwal

lib/ModelingToolkitBase/src/systems/analysis_points.jl

@@ -459,6 +459,7 @@ function get_analysis_variable(var, name, iv; perturb = true)
         pvar = unwrap(only(@variables $name(iv)::T))
         default = zero(T)
     end
+    pvar = SU.setmetadata(pvar, AnalysisVariable, true)
     return pvar, default
 end
 

lib/ModelingToolkitBase/src/variables.jl

@@ -45,6 +45,12 @@ struct VariableMisc end
 struct VariableUnshifted end
 struct VariableShift end
 struct VariableTimeDomain end
+"""
+    $TYPEDEF
+
+Metadata key used to mark variables introduced by analysis point transformations.
+"""
+struct AnalysisVariable end
 
 Symbolics.option_to_metadata_type(::Val{:unit}) = VariableUnit
 Symbolics.option_to_metadata_type(::Val{:connect}) = VariableConnectType