fix: raise ValueError when provided seed is out-of-bounds

src/lightning/fabric/utilities/seed.py

@@ -27,7 +27,8 @@ def seed_everything(seed: Optional[int] = None, workers: bool = False, verbose:
     Args:
         seed: the integer value seed for global random state in Lightning.
             If ``None``, it will read the seed from ``PL_GLOBAL_SEED`` env variable. If ``None`` and the
-            ``PL_GLOBAL_SEED`` env variable is not set, then the seed defaults to 0.
+            ``PL_GLOBAL_SEED`` env variable is not set, then the seed defaults to 0. If the seed is provided
+            as an integer but is not in bounds, a ValueError is raised.
         workers: if set to ``True``, will properly configure all dataloaders passed to the
             Trainer with a ``worker_init_fn``. If the user already provides such a function
             for their dataloaders, setting this argument will have no influence. See also:
@@ -50,8 +51,7 @@ def seed_everything(seed: Optional[int] = None, workers: bool = False, verbose:
         seed = int(seed)
 
     if not (min_seed_value <= seed <= max_seed_value):
-        rank_zero_warn(f"{seed} is not in bounds, numpy accepts from {min_seed_value} to {max_seed_value}")
-        seed = 0
+        raise ValueError(f"{seed} is not in bounds, numpy accepts from {min_seed_value} to {max_seed_value}")
 
     if verbose:
         log.info(rank_prefixed_message(f"Seed set to {seed}", _get_rank()))

tests/tests_fabric/utilities/test_seed.py

@@ -56,10 +56,9 @@ def test_invalid_seed():
 @mock.patch.dict(os.environ, {}, clear=True)
 @pytest.mark.parametrize("seed", [10e9, -10e9])
 def test_out_of_bounds_seed(seed):
-    """Ensure that we still fix the seed even if an out-of-bounds seed is given."""
-    with pytest.warns(UserWarning, match="is not in bounds"):
-        actual = seed_everything(seed)
-    assert actual == 0
+    """Ensure that a ValueError is raised if an out-of-bounds seed is given."""
+    with pytest.raises(ValueError, match="is not in bounds"):
+        seed_everything(seed)
 
 
 def test_reset_seed_no_op():