Refactor tests and imports to throw import error on environment creation

minigrid/__init__.py

@@ -5,6 +5,7 @@
 from minigrid import minigrid_env, wrappers
 from minigrid.core import roomgrid
 from minigrid.core.world_object import Wall
+from minigrid.envs.wfc.config import WFC_PRESETS
 
 __version__ = "2.3.0"
 
@@ -567,21 +568,11 @@ def register_minigrid_envs():
 
     # WaveFunctionCollapse
     # ----------------------------------------
-    try:
-        import imageio
-        import networkx
-
-        from minigrid.envs.wfc.config import WFC_PRESETS
-
-        for name in WFC_PRESETS.keys():
-            register(
-                id=f"MiniGrid-WFC-{name}-v0",
-                entry_point="minigrid.envs:WFCEnv",
-                kwargs={"wfc_config": name},
-            )
-    except ImportError:
-        print(
-            "networkx and/or imageio not found, skipping registering WFC environments"
+    for name in WFC_PRESETS.keys():
+        register(
+            id=f"MiniGrid-WFC-{name}-v0",
+            entry_point="minigrid.envs.wfc:WFCEnv",
+            kwargs={"wfc_config": name},
         )
 
     # BabyAI - Language based levels - GoTo

minigrid/envs/__init__.py

@@ -25,4 +25,3 @@
 from minigrid.envs.redbluedoors import RedBlueDoorEnv
 from minigrid.envs.unlock import UnlockEnv
 from minigrid.envs.unlockpickup import UnlockPickupEnv
-from minigrid.envs.wfc import WFCEnv

minigrid/envs/wfc/__init__.py

@@ -6,4 +6,19 @@
     WFC_PRESETS_SLOW,
     WFCConfig,
 )
-from minigrid.envs.wfc.wfcenv import WFCEnv
+
+# This is wrapped in a try-except block so the presets can be accessed for registration
+# Otherwise, importing here will fail when networkx is not installed
+try:
+    from minigrid.envs.wfc.wfcenv import WFCEnv
+except ImportError:
+
+    class WFCEnv:
+        """Dummy class to give a helpful error message when dependencies are missing"""
+
+        def __init__(self, *args, **kwargs):
+            from gymnasium.error import DependencyNotInstalled
+
+            raise DependencyNotInstalled(
+                'WFC dependencies are missing, please run `pip install "minigrid[wfc]"`'
+            )

minigrid/envs/wfc/config.py

@@ -3,16 +3,8 @@
 from dataclasses import asdict, dataclass
 from pathlib import Path
 
-from gymnasium.error import DependencyNotInstalled
 from typing_extensions import Literal
 
-try:
-    import imageio
-except ImportError as e:
-    raise DependencyNotInstalled(
-        'imageio is missing, please run `pip install "minigrid[wfc]"`'
-    ) from e
-
 PATTERN_PATH = Path(__file__).parent / "patterns"
 
 
@@ -48,8 +40,16 @@ class WFCConfig:
 
     @property
     def wfc_kwargs(self):
+        try:
+            from imageio.v2 import imread
+        except ImportError as e:
+            from gymnasium.error import DependencyNotInstalled
+
+            raise DependencyNotInstalled(
+                'imageio is missing, please run `pip install "minigrid[wfc]"`'
+            ) from e
         kwargs = asdict(self)
-        kwargs["image"] = imageio.v2.imread(kwargs.pop("pattern_path"))[:, :, :3]
+        kwargs["image"] = imread(kwargs.pop("pattern_path"))[:, :, :3]
         return kwargs
 
 

tests/utils.py

@@ -1,6 +1,8 @@
 """Finds all the specs that we can test with"""
 from __future__ import annotations
 
+from importlib.util import find_spec
+
 import gymnasium as gym
 import numpy as np
 
@@ -13,6 +15,14 @@
     )
 ]
 
+if find_spec("imageio") is None or find_spec("networkx") is None:
+    # Do not test WFC environments if dependencies are not installed
+    all_testing_env_specs = [
+        env_spec
+        for env_spec in all_testing_env_specs
+        if not env_spec.entry_point.startswith("minigrid.envs.wfc")
+    ]
+
 minigrid_testing_env_specs = [
     env_spec
     for env_spec in all_testing_env_specs