fix: fix cons_expr and expr fields of OptimizationFunction

Author: AayushSabharwal

src/problems/optimizationproblem.jl

@@ -58,10 +58,10 @@ function SciMLBase.OptimizationFunction{iip}(sys::System;
         else
             _cons_h = cons_hess_prototype = nothing
         end
-        cons_expr = cstr
+        cons_expr = Code.toexpr.(expand.([eq.lhs for eq in Symbolics.canonical_form.(cstr)]))
     end
 
-    obj_expr = cost(sys)
+    obj_expr = Code.toexpr(expand(cost(sys)))
 
     observedfun = ObservedFunctionCache(
         sys; expression, eval_expression, eval_module, checkbounds, cse)

test/optimizationsystem.jl

@@ -64,6 +64,8 @@ end
     sys = complete(sys)
     prob = OptimizationProblem(sys, [x => 0.0, y => 0.0, a => 1.0, b => 1.0],
         grad = true, hess = true, cons_j = true, cons_h = true)
+    @test prob.f.cons_expr isa Vector{Expr}
+    @test prob.f.expr isa Expr
     @test prob.f.sys === sys
     sol = solve(prob, IPNewton())
     @test sol.objective < 1.0