[Bug Report] Minigrid environment fails to step when SymbolicObsWrapper is used

[zidanwang2025]

Describe the bug

The Minigrid environment fails to step when SymbolicObsWrapper is used.

Code example

import gymnasium as gym
from minigrid.wrappers import RGBImgObsWrapper, SymbolicObsWrapper, ImgObsWrapper
env = gym.make('MiniGrid-Empty-8x8-v0')
env = SymbolicObsWrapper(env)
obs, info = env.reset()
count = 0
for i in range(10000):
    action = env.action_space.sample()
    next_obs, reward, terminated, truncated, info = env.step(action)
    if (next_obs['image'] != obs['image']).any():
        count += 1
        obs = next_obs
print(count)

The count I got from this code is 0. While next_obs['direction'] changes,next_obs['image'] stays the same when env.step(action) is called. This does not happen when RGBImgObsWrapper(env) is used instead.

System Info

• minigrid was installed using pip install minigrid.
• macOS Monterey Version 12.3.1 is used.
• Python 3.8 is used.

Checklist

• [x] I have checked that there is no similar issue in the repo (required)

[rodrigodelazcano]

Thank you for finding this, I got to replicate it and I'll fix it soon.

[rodrigodelazcano]

@zidanwang2025 UPDATE: the wrapper is actually correct. The issue is that the encoded observation doesn't include the agent, and the map is static. If you try your code with a dynamic environment like MiniGrid-Dynamic-Obstacles-5x5-v0 you'll find that the Symbolic observation is different.

However, I'll modify the wrapper to include the agent in order to have the complete state of the environment.

[zidanwang2025]

Thanks for the update!!