Call final_touch in optimize in CachingOptimizer

src/Utilities/cachingoptimizer.jl

@@ -298,6 +298,7 @@ MOI.is_empty(m::CachingOptimizer) = MOI.is_empty(m.model_cache)
 
 function MOI.optimize!(m::CachingOptimizer)
     if m.mode == AUTOMATIC && m.state == EMPTY_OPTIMIZER
+        final_touch(m.model_cache, nothing)
         # Here is a special case for callbacks: we can't use the two-argument
         # call to optimize! because we need the `optimizer_to_model_map` to be
         # set _prior_ to starting the optimization process. Therefore, we need

test/Utilities/cachingoptimizer.jl

@@ -914,6 +914,38 @@ function test_copy_optimizer_attributes_2887()
     return
 end
 
+mutable struct FinalTouchDetector <: MOI.ModelLike
+    index_map::Any
+end
+
+function MOI.Utilities.final_touch(model::FinalTouchDetector, index_map)
+    model.index_map = index_map
+    return
+end
+function MOI.copy_to(::MOI.Utilities.MockOptimizer, ::FinalTouchDetector)
+    return MOI.Utilities.IndexMap()
+end
+function MOI.get(::FinalTouchDetector, ::MOI.ListOfOptimizerAttributesSet)
+    return MOI.AbstractOptimizerAttribute[]
+end
+function MOI.get(::FinalTouchDetector, ::MOI.ListOfModelAttributesSet)
+    return MOI.AbstractModelAttribute[]
+end
+
+function test_final_touch_optimize()
+    model = MOI.Utilities.CachingOptimizer(
+        FinalTouchDetector(missing),
+        MOI.Utilities.MockOptimizer(MOI.Utilities.Model{Float64}()),
+    )
+    MOI.Utilities.attach_optimizer(model)
+    @test model.model_cache.index_map === nothing
+    MOI.Utilities.final_touch(model, missing)
+    @test model.model_cache.index_map === missing
+    MOI.Utilities.reset_optimizer(model)
+    MOI.optimize!(model)
+    @test model.model_cache.index_map === nothing
+end
+
 end  # module
 
 TestCachingOptimizer.runtests()