[tune] Support callable objects in variant generation (#6849)

* minorcallable

* format

python/ray/tune/suggest/variant_generator.py

@@ -2,7 +2,6 @@ import copy
 import logging
 import numpy
 import random
-import types
 
 from ray.tune import TuneError
 from ray.tune.sample import sample_from
@@ -126,7 +125,7 @@ def _generate_variants(spec):
     grid_vars = []
     lambda_vars = []
     for path, value in unresolved.items():
-        if isinstance(value, types.FunctionType):
+        if callable(value):
             lambda_vars.append((path, value))
         else:
             grid_vars.append((path, value))

python/ray/tune/tests/test_var.py

@@ -1,5 +1,6 @@
 import os
 import numpy as np
+import random
 import unittest
 
 import ray
@@ -210,6 +211,29 @@ class VariantGeneratorTest(unittest.TestCase):
         self.assertEqual(trials[0].config, {"x": 100, "y": 1})
         self.assertEqual(trials[1].config, {"x": 200, "y": 1})
 
+    def testDependentGridSearchCallable(self):
+        class Normal:
+            def __call__(self, _config):
+                return random.normalvariate(mu=0, sigma=1)
+
+        class Single:
+            def __call__(self, _config):
+                return 20
+
+        trials = self.generate_trials({
+            "run": "PPO",
+            "config": {
+                "x": grid_search(
+                    [tune.sample_from(Normal()),
+                     tune.sample_from(Normal())]),
+                "y": tune.sample_from(Single()),
+            },
+        }, "dependent_grid_search")
+        trials = list(trials)
+        self.assertEqual(len(trials), 2)
+        self.assertEqual(trials[0].config["y"], 20)
+        self.assertEqual(trials[1].config["y"], 20)
+
     def testNestedValues(self):
         trials = self.generate_trials({
             "run": "PPO",