Expose captureCons and releaseCons on Model

Author: Joao-Dionisio

src/pyscipopt/scip.pxi

@@ -8568,7 +8568,31 @@ cdef class Model:
 
         """
         PY_SCIP_CALL(SCIPdelConsLocal(self._scip, cons.scip_cons))
-    
+
+    def captureCons(self, Constraint cons):
+        """
+        Increase the usage counter of a constraint. Must be matched by a releaseCons.
+
+        Parameters
+        ----------
+        cons : Constraint
+            constraint to capture
+
+        """
+        PY_SCIP_CALL(SCIPcaptureCons(self._scip, cons.scip_cons))
+
+    def releaseCons(self, Constraint cons):
+        """
+        Decrease the usage counter of a constraint; frees it when the counter reaches zero.
+
+        Parameters
+        ----------
+        cons : Constraint
+            constraint to release
+
+        """
+        PY_SCIP_CALL(SCIPreleaseCons(self._scip, &cons.scip_cons))
+
     def getValsLinear(self, Constraint cons):
         """
         Retrieve the coefficients of a linear constraint

src/pyscipopt/scip.pyi

@@ -922,6 +922,7 @@ class Model:
     def calcNodeselPriority(
         self, variable: Incomplete, branchdir: Incomplete, targetvalue: Incomplete
     ) -> Incomplete: ...
+    def captureCons(self, cons: Incomplete) -> Incomplete: ...
     def catchEvent(
         self, eventtype: Incomplete, eventhdlr: Incomplete
     ) -> Incomplete: ...
@@ -1487,6 +1488,7 @@ class Model:
     def readSolFile(self, filename: Incomplete) -> Incomplete: ...
     def redirectOutput(self) -> Incomplete: ...
     def relax(self) -> Incomplete: ...
+    def releaseCons(self, cons: Incomplete) -> Incomplete: ...
     def releaseRow(self, row: Incomplete) -> Incomplete: ...
     def repropagateNode(self, node: Incomplete) -> Incomplete: ...
     def resetParam(self, name: Incomplete) -> Incomplete: ...

tests/test_cons.py

@@ -368,3 +368,22 @@ def test_getValsLinear():
 @pytest.mark.skip(reason="TODO: test getRowLinear()")
 def test_getRowLinear():
     assert True
+
+
+def test_captureCons_releaseCons():
+    m = Model()
+    x = m.addVar("x")
+    c = m.addCons(x <= 1)
+
+    # Pair capture+release: problem still holds its own capture, so this is safe.
+    m.captureCons(c)
+    m.releaseCons(c)
+
+    # Model continues to function — problem's capture survived.
+    m.optimize()
+    assert m.getStatus() == "optimal"
+
+    with pytest.raises(TypeError):
+        m.captureCons("not a constraint")
+    with pytest.raises(TypeError):
+        m.releaseCons("not a constraint")