Add value for constraints with a custom var_value function

src/constraints.jl

@@ -588,6 +588,11 @@ function value(con_ref::ConstraintRef{Model, <:_MOICON}; result::Int = 1)
     return reshape_vector(_constraint_primal(con_ref, result), con_ref.shape)
 end
 
+function value(con_ref::ConstraintRef{Model, <:_MOICON}, var_value::Function)
+    f = jump_function(constraint_object(con_ref))
+    return reshape_vector(value.(f, Ref(var_value)), con_ref.shape)
+end
+
 # Returns the value of MOI.ConstraintPrimal in a type-stable way
 function _constraint_primal(
     con_ref::ConstraintRef{

src/variables.jl

@@ -767,6 +767,10 @@ function value(v::VariableRef; result::Int = 1)::Float64
     return MOI.get(owner_model(v), MOI.VariablePrimal(result), v)
 end
 
+function value(v::VariableRef, var_value::Function)
+    return var_value(v)
+end
+
 """
     has_values(model::Model; result::Int = 1)
 

test/constraint.jl

@@ -663,6 +663,21 @@ function test_Model_add_to_function_constant_vector(::Any, ::Any)
     @test JuMP.moi_set(con) == MOI.Nonnegatives(2)
 end
 
+function test_Model_value_constraint_var(ModelType, ::Any)
+    model = ModelType()
+    @variable(model, x[1:2])
+    @constraint(model, c1, x[1] + x[2] <= 3.0)
+    @constraint(model, c2, x[1]^2 + x[2]^2 <= 3.0)
+    @constraint(model, c3, [1.0, x[1], x[2]] in SecondOrderCone())
+
+    vals = Dict(x[1] => 1.0, x[2] => 2.0)
+    f = vidx -> vals[vidx]
+
+    @test value(c1, f) === 3.0 # Affine expression
+    @test value(c2, f) === 5.0 # Quadratic expression
+    @test value(c3, f) == [1.0, 1.0, 2.0] # Vector expression
+end
+
 function _test_shadow_price_util(model_string, constraint_dual, constraint_shadow)
     model = Model()
     MOIU.loadfromstring!(backend(model), model_string)

test/variable.jl

@@ -713,6 +713,17 @@ function test_Model_value(::Any, ::Any)
     @test value(JuMP._MA.Zero()) === 0.0
 end
 
+function test_Model_value_var(ModelType, ::Any)
+    model = ModelType()
+    @variable(model, x[1:2])
+
+    vals = Dict(x[1] => 1.0, x[2] => 2.0)
+    f = vidx -> vals[vidx]
+
+    @test value(x[1], f) === 1.0
+    @test value(x[2], f) === 2.0
+end
+
 function test_Model_relax_integrality(::Any, ::Any)
     model = Model()
     @variable(model, x, Bin)