LpConstraint should have its own name (#806)

* LpConstraint should have its own name

* Add name to LpConstraint

* Add test for #805

Author: MBradbury

pulp/pulp.py

@@ -1061,9 +1061,8 @@ def __init__(self, e=None, sense=const.LpConstraintEQ, name=None, rhs=None):
         :param name: identifying string
         :param rhs: numerical value of constraint target
         """
-        self.expr = (
-            e if isinstance(e, LpAffineExpression) else LpAffineExpression(e, name=name)
-        )
+        self.expr = e if isinstance(e, LpAffineExpression) else LpAffineExpression(e)
+        self.name = name
         self.constant: float = self.expr.constant
         if rhs is not None:
             self.constant -= rhs
@@ -1265,12 +1264,15 @@ def fromDict(cls, _dict):
     from_dict = fromDict
 
     @property
-    def name(self):
-        return self.expr.name
+    def name(self) -> str | None:
+        return self.__name
 
     @name.setter
-    def name(self, v):
-        self.expr.name = v
+    def name(self, name: str | None):
+        if name is not None:
+            self.__name = name.translate(LpAffineExpression.trans)
+        else:
+            self.__name = None
 
     def isAtomic(self):
         return len(self) == 1 and self.constant == 0 and next(iter(self.values())) == 1

pulp/tests/test_pulp.py

@@ -1775,6 +1775,23 @@ def test_regression_794(self):
                     self.assertEqual(str(rhs), f"s_{t-1} + x_{t} - {demands[t-1]}")
                     self.assertEqual(expr.constant, -rhs.constant)
 
+        def test_regression_805(self):
+            # See: https://github.com/coin-or/pulp/issues/805
+
+            e = LpAffineExpression(1)
+            self.assertIsNone(e.name)
+
+            c = LpConstraint(e, name="Test2")
+            self.assertEqual(c.name, "Test2")
+            self.assertIsNone(c.expr.name)
+
+            e = LpAffineExpression(1, name="Test1")
+            self.assertEqual(e.name, "Test1")
+
+            c = LpConstraint(e, name="Test2")
+            self.assertEqual(c.name, "Test2")
+            self.assertEqual(c.expr.name, "Test1")
+
 
 class PULP_CBC_CMDTest(BaseSolverTest.PuLPTest):
     solveInst = PULP_CBC_CMD