From 3ce529883c7ab4e42dd4fac7a3e801912aa5c3da Mon Sep 17 00:00:00 2001
From: phi <phi.friday@gmail.com>
Date: Sun, 8 Sep 2024 20:08:28 +0900
Subject: [PATCH] fix: allow null target_func

---
 bayes_opt/acquisition.py           | 2 +-
 bayes_opt/bayesian_optimization.py | 4 ++--
 bayes_opt/target_space.py          | 7 +++++--
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/bayes_opt/acquisition.py b/bayes_opt/acquisition.py
index 6d330df0..1cf22c9f 100644
--- a/bayes_opt/acquisition.py
+++ b/bayes_opt/acquisition.py
@@ -804,7 +804,7 @@ def _copy_target_space(self, target_space: TargetSpace) -> TargetSpace:
         keys = target_space.keys
         pbounds = {key: bound for key, bound in zip(keys, target_space.bounds)}
         target_space_copy = TargetSpace(
-            None,  # FIXME
+            None,
             pbounds=pbounds,
             constraint=target_space.constraint,
             allow_duplicate_points=target_space._allow_duplicate_points,
diff --git a/bayes_opt/bayesian_optimization.py b/bayes_opt/bayesian_optimization.py
index 46017105..bb7e93b5 100644
--- a/bayes_opt/bayesian_optimization.py
+++ b/bayes_opt/bayesian_optimization.py
@@ -79,7 +79,7 @@ class BayesianOptimization(Observable):
 
     Parameters
     ----------
-    f: function
+    f: function or None.
         Function to be maximized.
 
     pbounds: dict
@@ -110,7 +110,7 @@ class BayesianOptimization(Observable):
 
     def __init__(
         self,
-        f: Callable[..., float],
+        f: Callable[..., float] | None,
         pbounds: Mapping[str, tuple[float, float]],
         acquisition_function: AcquisitionFunction | None = None,
         constraint: Constraint | None = None,
diff --git a/bayes_opt/target_space.py b/bayes_opt/target_space.py
index a1036886..955e581c 100644
--- a/bayes_opt/target_space.py
+++ b/bayes_opt/target_space.py
@@ -33,7 +33,7 @@ class TargetSpace:
 
     Parameters
     ----------
-    target_func : function
+    target_func : function or None.
         Function to be maximized.
 
     pbounds : dict
@@ -64,7 +64,7 @@ class TargetSpace:
 
     def __init__(
         self,
-        target_func: Callable[..., float],
+        target_func: Callable[..., float] | None,
         pbounds: Mapping[str, tuple[float, float]],
         constraint: ConstraintModel | None = None,
         random_state: int | np.random.RandomState | None = None,
@@ -406,6 +406,9 @@ def probe(self, params: Any) -> float | tuple[float, float | NDArray[Float]]:
             return self._cache[_hashable(x.ravel())]
 
         dict_params = self.array_to_params(x)
+        if self.target_func is None:
+            error_msg = "No target function has been provided."
+            raise ValueError(error_msg)
         target = self.target_func(**dict_params)
 
         if self._constraint is None: