Make lupa an optional dependency.

kurobako/problem.py

@@ -2,14 +2,21 @@
 import copy
 import enum
 import json
-from lupa import LuaRuntime
 import numpy as np
 from typing import Any
 from typing import Dict
 from typing import List
 from typing import Optional
 from typing import Union
 
+try:
+    from lupa import LuaRuntime
+
+    _lupa_available = True
+except ImportError:
+    _lupa_available = False
+
+
 Self = Any
 
 
@@ -150,6 +157,11 @@ def is_constraint_satisfied(self, vars: List[Self], vals: List[Optional[float]])
         if self.constraint is None:
             return True
 
+        if not _lupa_available:
+            raise RuntimeError(
+                "Please install `lupa` to handle problems containing conditional search space."
+            )
+
         lua = LuaRuntime()
         for var, val in zip(vars, vals):
             if val is None:

setup.py

@@ -20,6 +20,6 @@ def get_long_description() -> str:
     url="https://github.com/sile/kurobako-py",
     license="MIT",
     packages=find_packages(),
-    install_requires=["lupa", "numpy"],
+    install_requires=["numpy"],
     extras_require={"checking": ["hacking", "mypy", "black"]},
 )