Raise an exception when serializing CQMs with bad labels

Closes #1358

dimod/constrained/constrained.py

@@ -1785,6 +1785,16 @@ def to_file(self, *,
  # put everything in a constraints/label/ directory
  lstr = json.dumps(serialize_variable(label))
 
+ # We want to disallow invalid filenames. We do this via a blacklist
+ # rather than a whitelist to be as permissive as possible. If we find enough
+ # other edge cases, we can switch in the future.
+ # Also, if we find that raising an error places an undue burden on users, we can
+ # switch to a scheme where invalid names are saved as files with generic directory
+ # labels.
+ if "/" in lstr:
+ # NULL actually passes fine because of the JSON dumps
+ raise ValueError("Cannot serialize constraint labels containing '/'")
+
  with zf.open(f'constraints/{lstr}/lhs', "w", force_zip64=True) as fdst:
  constraint.lhs._into_file(fdst)
 

releasenotes/notes/fix-constraint-labels-and-serialization-c0eb5e410293a63c.yaml

@@ -0,0 +1,6 @@
+---
+fixes:
+ - |
+ Raise an exception when serializing constrained quadratic models with constraint
+ labels that are not legal file names.
+ See `#1358 <https://github.com/dwavesystems/dimod/issues/1358>`_.

tests/test_constrained.py

@@ -1334,6 +1334,34 @@ def test_unused_variable(self):
  self.assertEqual(new.lower_bound(v), cqm.lower_bound(v))
  self.assertEqual(new.upper_bound(v), cqm.upper_bound(v))
 
+ def test_unusual_constraint_labels(self):
+ x, y = dimod.Binaries("xy")
+
+ with self.subTest("/"):
+ cqm = dimod.CQM()
+ cqm.add_constraint(x + y <= 5, label="hello/world")
+ with self.assertRaises(ValueError):
+ cqm.to_file()
+
+ # NULL actually works because it's passed through JSON
+ with self.subTest("NULL"):
+ cqm = dimod.CQM()
+ cqm.add_constraint(x + y <= 5, label="hello\0world")
+ with cqm.to_file() as f:
+ new = dimod.CQM.from_file(f)
+
+ self.assertEqual(list(new.constraints), ["hello\0world"])
+
+ # a few other potentially tricky characters, not exhaustive
+ for c in ";,\\>|😜+-&":
+ with self.subTest(c):
+ cqm = dimod.CQM()
+ cqm.add_constraint(x + y <= 5, label=f"hello{c}world")
+ with cqm.to_file() as f:
+ new = dimod.CQM.from_file(f)
+
+ self.assertEqual(list(new.constraints), [f"hello{c}world"])
+
 
 class TestSetObjective(unittest.TestCase):
  def test_bqm(self):