Model Writing Error Messages

[ccoffrin]

Given this model,

m = Model()
@variable(m, x)
@objective(m, Min, x^2)

The command, write_to_file(m, "model.lp") yields,

ERROR: MethodError: no method matching write_function(::IOStream, ::MathOptInterface.FileFormats.LP.Model{Float64}, ::MathOptInterface.ScalarQuadraticFunction{Float64}, ::Dict{MathOptInterface.VariableIndex,String})

The command, write_to_file(m, "model.mps") yields,

ERROR: MethodError: no method matching extract_terms(::MathOptInterface.FileFormats.MPS.Model{Float64}, ::Dict{String,Array{Tuple{String,Float64},1}}, ::String, ::MathOptInterface.ScalarQuadraticFunction{Float64}, ::Set{String})

Could these messages be improved? Maybe something like, format X does not support constraint type Y?

[odow]

These examples should have failed on the MOI.copy_to, but they didn't for some reason.

MathOptInterface.jl/src/FileFormats/LP/LP.jl

Lines 6 to 16 in 26e0af4

	MOI.Utilities.@model(Model,
	(MOI.ZeroOne, MOI.Integer),
	(MOI.EqualTo, MOI.GreaterThan, MOI.LessThan, MOI.Interval),
	(),
	(),
	(),
	(MOI.ScalarAffineFunction,),
	(),
	()
	)

[blegat]

MOIU.Model supports SingleVariable, ScalarAffineFunction and ScalarQuadraticFunction as objective by default:

MathOptInterface.jl/src/Utilities/model.jl

Lines 411 to 418 in 26e0af4

	function MOI.supports(
	model::AbstractModel{T},
	::MOI.ObjectiveFunction{<:Union{
	MOI.SingleVariable,
	MOI.ScalarAffineFunction{T},
	MOI.ScalarQuadraticFunction{T}}}) where T
	return true
	end

The following method should be added to the file MathOptInterface.jl/src/FileFormats/LP/LP.jl:

MOI.supports(::Model{T}, ::MOI.ObjectiveFunction{<:Union{MOI.SingleVariable, MOI.ScalarQuadraticFunction{T}}}) where T = false