Test modification errors

src/modifications.jl

@@ -1,6 +1,6 @@
 """
     struct ModifyConstraintNotAllowed{F<:AbstractFunction, S<:AbstractSet,
-                                             C<:AbstractFunctionModification} <: NotAllowedError
+                                      C<:AbstractFunctionModification} <: NotAllowedError
         constraint_index::ConstraintIndex{F, S}
         change::C
         message::String
@@ -10,15 +10,18 @@ An error indicating that the constraint modification `change` cannot be applied
 to the constraint of index `ci`.
 """
 struct ModifyConstraintNotAllowed{F<:AbstractFunction, S<:AbstractSet,
-                                         C<:AbstractFunctionModification} <: NotAllowedError
+                                  C<:AbstractFunctionModification} <: NotAllowedError
     constraint_index::ConstraintIndex{F, S}
     change::C
     message::String
 end
-function ModifyConstraintNotAllowed(ci::ConstraintIndex{F, S},
-                                change::AbstractFunctionModification) where {F<:AbstractFunction, S<:AbstractSet}
-    ModifyConstraintNotAllowed{F, S, typeof(change)}(ci, change, "")
+function ModifyConstraintNotAllowed(
+    ci::ConstraintIndex{F, S},
+    change::AbstractFunctionModification,
+    message="") where {F<:AbstractFunction, S<:AbstractSet}
+    ModifyConstraintNotAllowed{F, S, typeof(change)}(ci, change, message)
 end
+throw_modify_not_allowed(ci::ConstraintIndex, args...) = throw(ModifyConstraintNotAllowed(ci, args...))
 
 operation_name(err::ModifyConstraintNotAllowed{F, S}) where {F, S} = "Modifying the constraints $(err.constraint_index) with $(err.change)"
 
@@ -38,6 +41,7 @@ end
 function ModifyObjectiveNotAllowed(change::AbstractFunctionModification)
     ModifyObjectiveNotAllowed(change, "")
 end
+throw_modify_not_allowed(::ObjectiveFunction, args...) = throw(ModifyObjectiveNotAllowed(args...))
 
 operation_name(err::ModifyObjectiveNotAllowed) = "Modifying the objective function with $(err.change)"
 
@@ -75,12 +79,12 @@ modify(model, ObjectiveFunction{ScalarAffineFunction{Float64}}(), ScalarConstant
 """
 function modify end
 
-function modify(model::ModelLike, ci::ConstraintIndex{F, S},
-                 change::AbstractFunctionModification) where {F, S}
-    throw(ModifyConstraintNotAllowed(ci, change))
+function modify(model::ModelLike, ci::ConstraintIndex,
+                change::AbstractFunctionModification)
+    throw_modify_not_allowed(ci, change)
 end
 
-function modify(model::ModelLike, ::ObjectiveFunction,
-                 change::AbstractFunctionModification)
-    throw(ModifyObjectiveNotAllowed(change))
+function modify(model::ModelLike, attr::ObjectiveFunction,
+                change::AbstractFunctionModification)
+    throw_modify_not_allowed(attr, change)
 end

test/errors.jl

@@ -1,3 +1,9 @@
+using Test
+using MathOptInterface
+const MOI = MathOptInterface
+
+include("dummy.jl")
+
 @testset "Fallbacks for `set` methods" begin
     model = DummyModel()
 
@@ -182,6 +188,32 @@
             MOI.set(model, MOI.ConstraintSet(), ci, MOI.GreaterThan(1.0))
         end
     end
+
+    @testset "ModifyNotAllowed" begin
+        change = MOI.ScalarConstantChange(1.0)
+        @testset "Constraint" begin
+            err = MOI.ModifyConstraintNotAllowed(ci, change)
+            @test_throws err MOI.modify(model, ci, change)
+            @test sprint(showerror, err) == "MathOptInterface.ModifyConstraintNotAllowed{MathOptInterface.SingleVariable,MathOptInterface.EqualTo{Float64},MathOptInterface.ScalarConstantChange{Float64}}:" *
+            " Modifying the constraints MathOptInterface.ConstraintIndex{MathOptInterface.SingleVariable,MathOptInterface.EqualTo{Float64}}(1)" *
+            " with MathOptInterface.ScalarConstantChange{Float64}(1.0) cannot" *
+            " be performed. You may want to use a `CachingOptimizer` in" *
+            " `AUTOMATIC` mode or you may need to call `reset_optimizer`" *
+            " before doing this operation if the `CachingOptimizer` is in" *
+            " `MANUAL` mode."
+        end
+        @testset "Objective" begin
+            attr = MOI.ObjectiveFunction{MOI.SingleVariable}()
+            err = MOI.ModifyObjectiveNotAllowed(change)
+            @test_throws err MOI.modify(model, attr, change)
+            @test sprint(showerror, err) == "MathOptInterface.ModifyObjectiveNotAllowed{MathOptInterface.ScalarConstantChange{Float64}}:" *
+            " Modifying the objective function with MathOptInterface.ScalarConstantChange{Float64}(1.0)" *
+            " cannot be performed. You may want to use a `CachingOptimizer`" *
+            " in `AUTOMATIC` mode or you may need to call `reset_optimizer`" *
+            " before doing this operation if the `CachingOptimizer` is in" *
+            " `MANUAL` mode."
+        end
+    end
 end
 
 @testset "Error messages" begin