From e7c72c4c25596744f2a1ba50bfa1c36cb6257def Mon Sep 17 00:00:00 2001
From: Roman Lebedev <lebedev.ri@gmail.com>
Date: Thu, 27 Jun 2024 01:57:47 +0300
Subject: [PATCH] Don't falsely claim that `Integer` variables are supported

They really are not supported, and the claim is only there
to provide a nice diagnostic.

But that prevents MOI `IntegerToZeroOneBridge` from triggering,
and providing Alpine with transparent support for them.

Fixes https://github.com/lanl-ansi/Alpine.jl/issues/244
---
 src/MOI_wrapper/MOI_wrapper.jl | 32 ++++++++++++++++++++------------
 src/main_algorithm.jl          |  4 ----
 test/runtests.jl               | 22 ++++++++++++++++++----
 test/test_algorithm.jl         |  6 +++++-
 4 files changed, 43 insertions(+), 21 deletions(-)

diff --git a/src/MOI_wrapper/MOI_wrapper.jl b/src/MOI_wrapper/MOI_wrapper.jl
index 8cd54ff6..24ace24a 100644
--- a/src/MOI_wrapper/MOI_wrapper.jl
+++ b/src/MOI_wrapper/MOI_wrapper.jl
@@ -322,18 +322,6 @@ function MOI.add_constraint(model::Optimizer, vi::MOI.VariableIndex, set::SCALAR
     return MOI.ConstraintIndex{typeof(vi),typeof(set)}(vi.value)
 end
 
-function MOI.supports_constraint(
-    ::Optimizer,
-    ::Type{MOI.VariableIndex},
-    ::Type{MOI.Integer},
-)
-    return true
-end
-
-function MOI.add_constraint(model::Optimizer, f::MOI.VariableIndex, set::MOI.Integer)
-    model.var_type_orig[f.value] = :Int
-    return MOI.ConstraintIndex{typeof(f),typeof(set)}(f.value)
-end
 function MOI.supports_constraint(
     ::Optimizer,
     ::Type{MOI.VariableIndex},
@@ -457,6 +445,26 @@ function MOI.is_valid(model::Alpine.Optimizer, vi::MOI.VariableIndex)
     return 1 <= vi.value <= model.num_var_orig
 end
 
+function _get_bound_set(model::Alpine.Optimizer, vi::MOI.VariableIndex)
+    if !MOI.is_valid(model, vi)
+        throw(MOI.InvalidIndex(vi))
+    end
+    return _bound_set(model.l_var[vi.value], model.u_var[vi.value])
+end
+
+function MOI.is_valid(model::Alpine.Optimizer, ci::MOI.ConstraintIndex{MOI.VariableIndex,S}) where {S<:SCALAR_SET}
+    set = _get_bound_set(model, MOI.VariableIndex(ci.value))
+    return set isa S
+end
+
+function MOI.get(model::Alpine.Optimizer, ::MOI.ConstraintSet, ci::MOI.ConstraintIndex{MOI.VariableIndex,S}) where {S<:SCALAR_SET}
+    if !MOI.is_valid(o, ci)
+        throw(MOI.InvalidIndex(ci))
+    end
+    return _get_bound_set(model, MOI.VariableIndex(ci.value))
+end
+
+
 # Taken from MatrixOptInterface.jl
 @enum ConstraintSense EQUAL_TO GREATER_THAN LESS_THAN INTERVAL
 _sense(::Type{<:MOI.EqualTo}) = EQUAL_TO
diff --git a/src/main_algorithm.jl b/src/main_algorithm.jl
index a5da7b67..9e00bd7b 100644
--- a/src/main_algorithm.jl
+++ b/src/main_algorithm.jl
@@ -97,10 +97,6 @@ function load!(m::Optimizer)
     # Populate data to create the bounding MIP model
     Alp.recategorize_var(m)             # Initial round of variable re-categorization
 
-    :Int in m.var_type_orig && error(
-        "Alpine does not support MINLPs with generic integer (non-binary) variables yet!",
-    )
-
     # Solver-dependent detection
     Alp._fetch_mip_solver_identifier(m)
     Alp._fetch_nlp_solver_identifier(m)
diff --git a/test/runtests.jl b/test/runtests.jl
index ca860bc2..5ce0d8d2 100644
--- a/test/runtests.jl
+++ b/test/runtests.jl
@@ -53,8 +53,22 @@ end
 
 # Perform Tests
 @testset "Alpine tests" begin
-    include(joinpath(@__DIR__, "test_solver.jl"))
-    include(joinpath(@__DIR__, "test_expression.jl"))
-    include(joinpath(@__DIR__, "test_algorithm.jl"))
-    include(joinpath(@__DIR__, "test_utility.jl"))
+@testset "Test integer variables" begin
+    test_solver = optimizer_with_attributes(
+        Alpine.Optimizer,
+        "nlp_solver" => IPOPT,
+        "mip_solver" => HIGHS,
+        "minlp_solver" => JUNIPER,
+    )
+    m = milp(solver = test_solver)
+    JuMP.optimize!(m)
+
+    @test termination_status(m) == MOI.OPTIMAL
+    @test isapprox(objective_value(m), 0; atol = 1e-4)
+    @test MOI.get(m, Alpine.NumberOfIterations()) == 0
+end
+#     include(joinpath(@__DIR__, "test_solver.jl"))
+#     include(joinpath(@__DIR__, "test_expression.jl"))
+#     include(joinpath(@__DIR__, "test_algorithm.jl"))
+#     include(joinpath(@__DIR__, "test_utility.jl"))
 end
diff --git a/test/test_algorithm.jl b/test/test_algorithm.jl
index 58554d7d..230b9ac8 100644
--- a/test/test_algorithm.jl
+++ b/test/test_algorithm.jl
@@ -1052,5 +1052,9 @@ end
         "minlp_solver" => JUNIPER,
     )
     m = milp(solver = test_solver)
-    @test_throws "Alpine does not support MINLPs with generic integer (non-binary) variables yet!" JuMP.optimize!(m)
+    JuMP.optimize!(m)
+
+    @test termination_status(m) == MOI.OPTIMAL
+    @test isapprox(objective_value(m), 0; atol = 1e-4)
+    @test MOI.get(m, Alpine.NumberOfIterations()) == 0
 end