[POC] Allow array in nonlinear expressions

Author: blegat

src/nlp_expr.jl

@@ -575,6 +575,8 @@ function moi_function(f::GenericNonlinearExpr{V}) where {V}
     for i in length(f.args):-1:1
         if f.args[i] isa GenericNonlinearExpr{V}
             push!(stack, (ret, i, f.args[i]))
+        elseif f.args[i] isa AbstractArray
+            ret.args[i] = moi_function.(f.args[i])
         else
             ret.args[i] = moi_function(f.args[i])
         end
@@ -586,6 +588,8 @@ function moi_function(f::GenericNonlinearExpr{V}) where {V}
         for j in length(arg.args):-1:1
             if arg.args[j] isa GenericNonlinearExpr{V}
                 push!(stack, (child, j, arg.args[j]))
+            elseif arg.args[j] isa AbstractArray
+                child.args[j] = moi_function.(arg.args[j])
             else
                 child.args[j] = moi_function(arg.args[j])
             end
@@ -611,6 +615,8 @@ function jump_function(model::GenericModel, f::MOI.ScalarNonlinearFunction)
             for child in reverse(arg.args)
                 push!(stack, (new_ret, child))
             end
+        elseif arg isa AbstractArray
+            push!(parent.args, jump_function.(model, arg))
         else
             push!(parent.args, jump_function(model, arg))
         end

test/test_nlp_expr.jl

@@ -6,6 +6,7 @@
 module TestNLPExpr
 
 using JuMP
+using LinearAlgebra
 using Test
 
 import LinearAlgebra
@@ -1232,4 +1233,14 @@ function test_extension_euler_to_exp(
     return
 end
 
+function test_array()
+    model = Model()
+    @variable(model, x)
+    op_norm = NonlinearOperator(:det, det)
+    @objective(model, Min, op_norm([x]))
+    f = MOI.get(model, MOI.ObjectiveFunction{MOI.ScalarNonlinearFunction}())
+    @test f.head == :norm
+    @test f.args == [[index(x)]]
+end
+
 end  # module