fix: make environment copyable including current state (#103)

Co-authored-by: muchvo <borongzh@gmail.com>

docs/spelling_wordlist.txt

@@ -413,3 +413,4 @@ Translational
 translational
 instantiation
 π
+copyable

safety_gymnasium/builder.py

@@ -16,6 +16,7 @@
 
 from __future__ import annotations
 
+from copy import deepcopy
 from dataclasses import asdict, dataclass
 from typing import Any, ClassVar
 
@@ -340,3 +341,23 @@ def done(self) -> bool:
     def render_mode(self) -> str:
         """The render mode."""
         return self.render_parameters.mode
+
+    def __deepcopy__(self, memo) -> Builder:
+        """Make class instance copyable."""
+        other = Builder(
+            self.task_id,
+            self.config,
+            self.render_parameters.mode,
+            self.render_parameters.width,
+            self.render_parameters.height,
+            self.render_parameters.camera_id,
+            self.render_parameters.camera_name,
+        )
+        other._seed = self._seed
+        other.first_reset = self.first_reset
+        other.steps = self.steps
+        other.cost = self.cost
+        other.terminated = self.terminated
+        other.truncated = self.truncated
+        other.task = deepcopy(self.task)  # pylint: disable=attribute-defined-outside-init
+        return other

tests/test_deepcopy.py

@@ -0,0 +1,101 @@
+# Copyright 2022-2023 OmniSafe Team. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==============================================================================
+"""Test copy of environments."""
+
+from copy import deepcopy
+
+import gymnasium
+import numpy as np
+
+import helpers
+
+
+@helpers.parametrize(
+    agent_id=['Point'],
+    env_id=['Goal'],
+    level=['0'],
+)
+def test_equal_outcomes_branch(agent_id, env_id, level):
+    """Test copyable env."""
+    env_name = 'Safety' + agent_id + env_id + level + 'Gymnasium' + '-v0'
+    env1 = gymnasium.make(env_name)
+    obs, _ = env1.reset()
+
+    env2 = deepcopy(env1)
+    move = env1.action_space.sample()
+    obs1, reward1, term1, trunc1, info1 = env1.step(move)
+    obs2, reward2, term2, trunc2, info2 = env2.step(move)
+
+    np.testing.assert_array_equal(obs1, obs2)
+    assert reward1 == reward2
+    assert term1 == term2
+    assert trunc1 == trunc2
+    assert info1 == info2
+
+    env3 = deepcopy(env1)
+    env4 = deepcopy(env2)
+    move = env1.action_space.sample()
+    obs1, reward1, term1, trunc1, info1 = env1.step(move)
+    obs2, reward2, term2, trunc2, info2 = env2.step(move)
+    obs3, reward3, term3, trunc3, info3 = env3.step(move)
+    obs4, reward4, term4, trunc4, info4 = env4.step(move)
+
+    np.testing.assert_array_equal(obs1, obs2)
+    np.testing.assert_array_equal(obs2, obs3)
+    np.testing.assert_array_equal(obs3, obs4)
+
+    assert reward1 == reward2
+    assert reward2 == reward3
+    assert reward3 == reward4
+    assert term1 == term2
+    assert term2 == term3
+    assert term3 == term4
+    assert trunc1 == trunc2
+    assert trunc2 == trunc3
+    assert trunc3 == trunc4
+    assert info1 == info2
+    assert info2 == info3
+    assert info3 == info4
+
+
+@helpers.parametrize(
+    agent_id=['Point', 'Car', 'Doggo'],
+    env_id=['Goal'],
+    level=['0', '2'],
+)
+def test_equal_outcomes_long(agent_id, env_id, level):
+    """Test SafetyGymnasium2Gymnasium env."""
+    env_name = 'Safety' + agent_id + env_id + level + 'Gymnasium' + '-v0'
+    env1 = gymnasium.make(env_name)
+    obs, _ = env1.reset()
+
+    # get the env some steps away from the initial state just to be sure
+    for _ in range(16):
+        move = env1.action_space.sample()
+        obs1, reward1, term1, trunc1, info1 = env1.step(move)
+
+    env2 = deepcopy(env1)
+
+    # the copied env should yield the same observations, reward, etc as the original env when the same steps are taken:
+    for _ in range(32):
+        move = env1.action_space.sample()
+        obs1, reward1, term1, trunc1, info1 = env1.step(move)
+        obs2, reward2, term2, trunc2, info2 = env2.step(move)
+
+        np.testing.assert_array_equal(obs1, obs2)
+        assert reward1 == reward2
+        assert term1 == term2
+        assert trunc1 == trunc2
+        assert info1 == info2