[Utilities] Fix getter in UniversalFallback

src/FileFormats/MOF/nonlinear.jl

@@ -62,12 +62,9 @@ function write_nlpblock(
     model::Model,
     name_map::Dict{MOI.VariableIndex,String},
 ) where {T<:Object}
-    # TODO(odow): is there a better way of checking if the NLPBlock is set?
-    nlp_block = try
-        MOI.get(model, MOI.NLPBlock())
-    catch ex
-        @assert isa(ex, KeyError)
-        return  # No NLPBlock set.
+    nlp_block = MOI.get(model, MOI.NLPBlock())
+    if nlp_block === nothing
+        return
     end
     MOI.initialize(nlp_block.evaluator, [:ExprGraph])
     variables = MOI.get(model, MOI.ListOfVariableIndices())

src/FileFormats/NL/NL.jl

@@ -243,9 +243,10 @@ MOI.initialize(::_LinearNLPEvaluator, ::Vector{Symbol}) = nothing
 function MOI.copy_to(dest::Model, model::MOI.ModelLike)
     mapping = MOI.Utilities.IndexMap()
     # Initialize the NLP block.
-    nlp_block = try
+    has_nlp = MOI.NLPBlock() in MOI.get(model, MOI.ListOfModelAttributesSet())
+    nlp_block = if has_nlp
         MOI.get(model, MOI.NLPBlock())
-    catch
+    else
         MOI.NLPBlockData(MOI.NLPBoundsPair[], _LinearNLPEvaluator(), false)
     end
     if !(:ExprGraph in MOI.features_available(nlp_block.evaluator))

src/Utilities/print.jl

@@ -483,6 +483,9 @@ end
 function _nlp_block(model::MOI.ModelLike)
     try
         block = MOI.get(model, MOI.NLPBlock())
+        if block === nothing
+            return
+        end
         if :ExprGraph in MOI.features_available(block.evaluator)
             MOI.initialize(block.evaluator, [:ExprGraph])
         end

src/Utilities/universalfallback.jl

@@ -258,10 +258,12 @@ end
 
 # Attributes
 function _get(uf::UniversalFallback, attr::MOI.AbstractOptimizerAttribute)
-    return uf.optattr[attr]
+    return get(uf.optattr, attr, nothing)
 end
 
-_get(uf::UniversalFallback, attr::MOI.AbstractModelAttribute) = uf.modattr[attr]
+function _get(uf::UniversalFallback, attr::MOI.AbstractModelAttribute)
+    return get(uf.modattr, attr, nothing)
+end
 
 function _get(
     uf::UniversalFallback,

test/Utilities/universalfallback.jl

@@ -373,6 +373,13 @@ function test_show()
     return
 end
 
+function test_missing_attribute()
+    model = MOI.Utilities.UniversalFallback(MOI.Utilities.Model{Float64}())
+    @test MOI.get(model, MOI.Test.UnknownModelAttribute()) === nothing
+    @test MOI.get(model, MOI.TimeLimitSec()) === nothing
+    return
+end
+
 end  # module
 
 TestUniversalFallback.runtests()