Add one-arg observed dispatch

Author: YingboMa

src/structural_transformation/codegen.jl

@@ -318,14 +318,20 @@ function build_torn_function(sys;
             sol_states = sol_states,
             var2assignment = var2assignment
 
-            function generated_observed(obsvar, u, p, t)
+            function generated_observed(obsvar, args...)
                 obs = get!(dict, value(obsvar)) do
                     build_observed_function(state, obsvar, var_eq_matching, var_sccs,
                                             is_solver_state_idxs, assignments, deps,
                                             sol_states, var2assignment,
                                             checkbounds = checkbounds)
                 end
-                obs(u, p, t)
+                if args === ()
+                    let obs = obs
+                        (u, p, t) -> obs(u, p, t)
+                    end
+                else
+                    obs(args...)
+                end
             end
         end
 

src/systems/diffeqs/abstractodesystem.jl

@@ -328,20 +328,32 @@ function DiffEqBase.ODEFunction{iip, specialize}(sys::AbstractODESystem, dvs = s
     obs = observed(sys)
     observedfun = if steady_state
         let sys = sys, dict = Dict()
-            function generated_observed(obsvar, u, p, t = Inf)
+            function generated_observed(obsvar, args...)
                 obs = get!(dict, value(obsvar)) do
                     build_explicit_observed_function(sys, obsvar)
                 end
-                obs(u, p, t)
+                if args === ()
+                    let obs = obs
+                        (u, p, t = Inf) -> obs(u, p, t)
+                    end
+                else
+                    length(args) == 2 ? obs(args..., Inf) : obs(args...)
+                end
             end
         end
     else
         let sys = sys, dict = Dict()
-            function generated_observed(obsvar, u, p, t)
+            function generated_observed(obsvar, args...)
                 obs = get!(dict, value(obsvar)) do
                     build_explicit_observed_function(sys, obsvar; checkbounds = checkbounds)
                 end
-                obs(u, p, t)
+                if args === ()
+                    let obs = obs
+                        (u, p, t) -> obs(u, p, t)
+                    end
+                else
+                    obs(args...)
+                end
             end
         end
     end
@@ -424,11 +436,17 @@ function DiffEqBase.DAEFunction{iip}(sys::AbstractODESystem, dvs = states(sys),
 
     obs = observed(sys)
     observedfun = let sys = sys, dict = Dict()
-        function generated_observed(obsvar, u, p, t)
+        function generated_observed(obsvar, args...)
             obs = get!(dict, value(obsvar)) do
                 build_explicit_observed_function(sys, obsvar; checkbounds = checkbounds)
             end
-            obs(u, p, t)
+            if args === ()
+                let obs = obs
+                    (u, p, t) -> obs(u, p, t)
+                end
+            else
+                obs(args...)
+            end
         end
     end