From dfad9ca8c246414c76e970c1a4e28bad221c0c65 Mon Sep 17 00:00:00 2001
From: Oscar Dowson <o.dowson@gmail.com>
Date: Mon, 19 Oct 2026 17:41:47 +1300
Subject: [PATCH] [FileFormats.MPS] throw an error when the function constant
 is not zero

---
 src/FileFormats/MPS/write.jl     |  6 ++++
 test/FileFormats/MPS/test_MPS.jl | 58 ++++++++++++++++++++++++++++----
 2 files changed, 58 insertions(+), 6 deletions(-)

diff --git a/src/FileFormats/MPS/write.jl b/src/FileFormats/MPS/write.jl
index fc37bac531..d2de1a5470 100644
--- a/src/FileFormats/MPS/write.jl
+++ b/src/FileFormats/MPS/write.jl
@@ -260,6 +260,9 @@ function _collect_coefficients(
     for index in MOI.get(model, MOI.ListOfConstraintIndices{F,S}())
         row_name = MOI.get(model, MOI.ConstraintName(), index)
         func = MOI.get(model, MOI.ConstraintFunction(), index)
+        if !iszero(func.constant)
+            throw(MOI.ScalarFunctionConstantNotZero{T,F,S}(func.constant))
+        end
         _extract_terms(var_to_column, coefficients, row_name, func)
     end
     return
@@ -281,6 +284,9 @@ function _collect_indicator(
         func = MOI.get(model, MOI.ConstraintFunction(), index)
         funcs = MOI.Utilities.eachscalar(func)
         z = convert(MOI.VariableIndex, funcs[1])
+        if !iszero(func.constants[2])
+            throw(MOI.ScalarFunctionConstantNotZero{T,F,S}(func.constants[2]))
+        end
         _extract_terms(var_to_column, coefficients, row_name, funcs[2])
         condition = _activation_condition(S)
         var_name = _var_name(model, z, var_to_column[z], options.generic_names)
diff --git a/test/FileFormats/MPS/test_MPS.jl b/test/FileFormats/MPS/test_MPS.jl
index 44e88b318f..6203ffca19 100644
--- a/test/FileFormats/MPS/test_MPS.jl
+++ b/test/FileFormats/MPS/test_MPS.jl
@@ -13,12 +13,9 @@ import MathOptInterface.FileFormats: MPS
 import OrderedCollections: OrderedDict
 
 function runtests()
-    for name in names(@__MODULE__; all = true)
-        if startswith("$(name)", "test_")
-            @testset "$name" begin
-                getfield(@__MODULE__, name)()
-            end
-        end
+    is_test(name) = startswith("$name", "test_")
+    @testset "$name" for name in filter(is_test, names(@__MODULE__; all = true))
+        getfield(@__MODULE__, name)()
     end
     return
 end
@@ -1926,6 +1923,55 @@ function test_semi_reading_2()
     return
 end
 
+function test_scalar_function_constant_not_zero()
+    for input in [
+        """
+        variables: x
+        c: 1.0 * x + 2.0 >= 3.0
+        """,
+        """
+        variables: x
+        c: 1.0 * x * x + 2.0 >= 3.0
+        """,
+        """
+        variables: x
+        c: 1.0 * x + 2.0 <= 3.0
+        """,
+        """
+        variables: x
+        c: 1.0 * x * x + 2.0 <= 3.0
+        """,
+        """
+        variables: x
+        c: 1.0 * x + 2.0 == 3.0
+        """,
+        """
+        variables: x
+        c: 1.0 * x * x + 2.0 == 3.0
+        """,
+        """
+        variables: x, z
+        c: [z, 1.0 * x + 2.0] in Indicator{ACTIVATE_ON_ONE}(LessThan(1.0))
+        z in ZeroOne()
+        """,
+        """
+        variables: x, z
+        c: [z, 1.0 * x + 2.0] in Indicator{ACTIVATE_ON_ONE}(GreaterThan(1.0))
+        z in ZeroOne()
+        """,
+        """
+        variables: x, z
+        c: [z, 1.0 * x + 2.0] in Indicator{ACTIVATE_ON_ONE}(EqualTo(1.0))
+        z in ZeroOne()
+        """,
+    ]
+        model = MPS.Model()
+        MOI.Utilities.loadfromstring!(model, input)
+        @test_throws(MOI.ScalarFunctionConstantNotZero, sprint(write, model))
+    end
+    return
+end
+
 end  # TestMPS
 
 TestMPS.runtests()