Update

src/objective.jl

@@ -450,7 +450,10 @@ function set_objective_coefficient(
     coeff::Real,
 ) where {T}
     if _nlp_objective_function(model) !== nothing
-        error("A nonlinear objective is already set in the model")
+        error(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        )
     end
     coeff_t = convert(T, coeff)::T
     F = objective_function_type(model)
@@ -527,9 +530,14 @@ function set_objective_coefficient(
     coeffs::AbstractVector{<:Real},
 ) where {T}
     if _nlp_objective_function(model) !== nothing
-        error("A nonlinear objective is already set in the model")
-    elseif length(variables) != length(coeffs)
-        msg = "The number of variables and coefficients must match"
+        error(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        )
+    end
+    n, m = length(variables), length(coeffs)
+    if !(n == m)
+        msg = "The number of variables ($n) and coefficients ($m) must match"
         throw(DimensionMismatch(msg))
     end
     F = objective_function_type(model)
@@ -605,7 +613,10 @@ function set_objective_coefficient(
     coeff::Real,
 ) where {T}
     if _nlp_objective_function(model) !== nothing
-        error("A nonlinear objective is already set in the model")
+        error(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        )
     end
     coeff_t = convert(T, coeff)::T
     F = moi_function_type(objective_function_type(model))
@@ -685,12 +696,17 @@ function set_objective_coefficient(
     coeffs::AbstractVector{<:Real},
 ) where {T}
     if _nlp_objective_function(model) !== nothing
-        error("A nonlinear objective is already set in the model")
-    elseif !(length(variables_1) == length(variables_2) == length(coeffs))
-        msg = "The number of variables and coefficients must match"
+        error(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        )
+    end
+    n1, n2, m = length(variables_1), length(variables_2), length(coeffs)
+    if !(n1 == n2 == m)
+        msg = "The number of variables ($n1, $n2) and coefficients ($m) must match"
         throw(DimensionMismatch(msg))
     end
-    coeffs_t = convert.(T, coeffs)::AbstractVector{<:T}
+    coeffs_t = convert.(T, coeffs)
     F = moi_function_type(objective_function_type(model))
     _set_objective_coefficient(model, variables_1, variables_2, coeffs_t, F)
     model.is_model_dirty = true

src/variables.jl

@@ -2607,8 +2607,9 @@ function set_normalized_coefficient(
     variables::AbstractVector{<:AbstractVariableRef},
     coeffs::AbstractVector{<:Number},
 ) where {T,F<:Union{MOI.ScalarAffineFunction{T},MOI.ScalarQuadraticFunction{T}}}
-    if !(length(constraints) == length(variables) == length(coeffs))
-        msg = "The number of constraints, variables and coefficients must match"
+    c, n, m = length(constraints), length(variables), length(coeffs)
+    if !(c == n == m)
+        msg = "The number of constraints ($c), variables ($n) and coefficients ($m) must match"
         throw(DimensionMismatch(msg))
     end
     model = owner_model(first(constraints))
@@ -2764,13 +2765,10 @@ function set_normalized_coefficient(
     variables_2::AbstractVector{<:AbstractVariableRef},
     coeffs::AbstractVector{<:Number},
 ) where {T,F<:MOI.ScalarQuadraticFunction{T}}
-    dimension_match =
-        length(constraints) ==
-        length(variables_1) ==
-        length(variables_2) ==
-        length(coeffs)
-    if !dimension_match
-        msg = "The number of constraints, variables and coefficients must match"
+    c, m = length(constraints), length(coeffs)
+    n1, n2 = length(variables_1), length(variables_1)
+    if !(c == n1 == n2 == m)
+        msg = "The number of constraints ($c), variables ($n1, $n2) and coefficients ($m) must match"
         throw(DimensionMismatch(msg))
     end
     new_coeffs = convert.(T, coeffs)

test/test_constraint.jl

@@ -1001,7 +1001,7 @@ function test_change_coefficient_batch()
     @test isequal_canonical(constraint_object(quad_con).func, x^2 + 2x + 7y)
     @test_throws(
         DimensionMismatch(
-            "The number of constraints, variables and coefficients must match",
+            "The number of constraints (1), variables (2) and coefficients (2) must match",
         ),
         set_normalized_coefficient([con_ref], [x, y], [4, 5]),
     )
@@ -1868,7 +1868,7 @@ function test_set_normalized_coefficient_quadratic_batch()
     @test normalized_coefficient(con, x[1], x[2]) == 5.0
     @test_throws(
         DimensionMismatch(
-            "The number of constraints, variables and coefficients must match",
+            "The number of constraints (1), variables (2, 2) and coefficients (2) must match",
         ),
         set_normalized_coefficient([con], [x[1], x[1]], [x[1], x[2]], [4, 5]),
     )

test/test_objective.jl

@@ -55,7 +55,10 @@ function test_objective_coef_update_linear_objective_error()
     @variable(model, x[1:2])
     @NLobjective(model, Min, x[1] * x[2])
     @test_throws(
-        ErrorException("A nonlinear objective is already set in the model"),
+        ErrorException(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        ),
         set_objective_coefficient(model, x[1], 2),
     )
     return
@@ -66,7 +69,10 @@ function test_objective_coef_update_linear_objective_batch_error()
     @variable(model, x[1:2])
     @NLobjective(model, Min, x[1] * x[2])
     @test_throws(
-        ErrorException("A nonlinear objective is already set in the model"),
+        ErrorException(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        ),
         set_objective_coefficient(model, [x[1], x[2]], [2, 3]),
     )
     return
@@ -78,7 +84,7 @@ function test_objective_coef_update_linear_objective_batch_dimension_error()
     @objective(model, Min, x[1] * x[2])
     @test_throws(
         DimensionMismatch(
-            "The number of variables and coefficients must match",
+            "The number of variables (2) and coefficients (1) must match",
         ),
         set_objective_coefficient(model, [x[1], x[2]], [2]),
     )
@@ -321,7 +327,10 @@ function test_set_objective_coefficient_quadratic_error()
     @variable(model, x[1:2])
     @NLobjective(model, Min, x[1] * x[2])
     @test_throws(
-        ErrorException("A nonlinear objective is already set in the model"),
+        ErrorException(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        ),
         set_objective_coefficient(model, x[1], x[1], 2),
     )
     return
@@ -332,7 +341,10 @@ function test_set_objective_coefficient_quadratic_batch_error()
     @variable(model, x[1:2])
     @NLobjective(model, Min, x[1] * x[2])
     @test_throws(
-        ErrorException("A nonlinear objective is already set in the model"),
+        ErrorException(
+            "A nonlinear objective created by the legacy `@NLobjective` is " *
+            "set in the model. This does not support modification.",
+        ),
         set_objective_coefficient(model, [x[1]], [x[1]], [2]),
     )
     return
@@ -344,7 +356,7 @@ function test_set_objective_coefficient_quadratic_batch_dimension_error()
     @objective(model, Min, x[1] * x[2])
     @test_throws(
         DimensionMismatch(
-            "The number of variables and coefficients must match",
+            "The number of variables (1, 1) and coefficients (2) must match",
         ),
         set_objective_coefficient(model, [x[1]], [x[1]], [2, 3]),
     )