From 23403291e53533def8b82b48039dbb091f4c2742 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 27 Dec 2022 17:40:48 +0100
Subject: [PATCH 01/15] FIX get config from dispatcher thread in delayed by
 default

---
 sklearn/_config.py     | 27 +++++++++++++++++++++------
 sklearn/utils/fixes.py | 18 +++++++++++-------
 2 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index e4c398c9c5444..b59922d366acc 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -4,7 +4,7 @@
 from contextlib import contextmanager as contextmanager
 import threading
 
-_global_config = {
+_global_config_default = {
     "assume_finite": bool(os.environ.get("SKLEARN_ASSUME_FINITE", False)),
     "working_memory": int(os.environ.get("SKLEARN_WORKING_MEMORY", 1024)),
     "print_changed_only": True,
@@ -17,19 +17,31 @@
     "transform_output": "default",
 }
 _threadlocal = threading.local()
+_thread_config = {}
 
 
 def _get_threadlocal_config():
-    """Get a threadlocal **mutable** configuration. If the configuration
-    does not exist, copy the default global configuration."""
+    """Get a threadlocal **mutable** configuration.
+
+    If the configuration does not exist, copy the default global configuration.
+    The configuration is also registered to in a global dictionary where the
+    key is the thread id.
+    """
     if not hasattr(_threadlocal, "global_config"):
-        _threadlocal.global_config = _global_config.copy()
+        _threadlocal.global_config = _global_config_default.copy()
+        _thread_config[threading.get_ident()] = _threadlocal.global_config
     return _threadlocal.global_config
 
 
-def get_config():
+def get_config(thread_id=None):
     """Retrieve current values for configuration set by :func:`set_config`.
 
+    Parameters
+    ----------
+    thread_id : int, default=None
+        The thread id from which to retrieve the configuration. If `None`,
+        the current thread id is used.
+
     Returns
     -------
     config : dict
@@ -42,7 +54,10 @@ def get_config():
     """
     # Return a copy of the threadlocal configuration so that users will
     # not be able to modify the configuration with the returned dict.
-    return _get_threadlocal_config().copy()
+    if thread_id is None:
+        return _get_threadlocal_config().copy()
+    _get_threadlocal_config()
+    return _thread_config[thread_id].copy()
 
 
 def set_config(
diff --git a/sklearn/utils/fixes.py b/sklearn/utils/fixes.py
index b43afa950a163..811f4c30da72c 100644
--- a/sklearn/utils/fixes.py
+++ b/sklearn/utils/fixes.py
@@ -14,6 +14,7 @@
 from importlib import resources
 import functools
 import sys
+import threading
 
 import sklearn
 import numpy as np
@@ -107,22 +108,25 @@ def _eigh(*args, **kwargs):
 
 
 # remove when https://github.com/joblib/joblib/issues/1071 is fixed
-def delayed(function):
+def delayed(func, thread_id=threading.get_ident()):
     """Decorator used to capture the arguments of a function."""
 
-    @functools.wraps(function)
-    def delayed_function(*args, **kwargs):
-        return _FuncWrapper(function), args, kwargs
+    def decorate(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kwargs):
+            return _FuncWrapper(func, thread_id=thread_id), args, kwargs
 
-    return delayed_function
+        return wrapper
+
+    return decorate(func)
 
 
 class _FuncWrapper:
     """ "Load the global configuration before calling the function."""
 
-    def __init__(self, function):
+    def __init__(self, function, thread_id=None):
         self.function = function
-        self.config = get_config()
+        self.config = get_config(thread_id=thread_id)
         update_wrapper(self, self.function)
 
     def __call__(self, *args, **kwargs):

From c7efddaef9f2a3b65d31e638515c81cad4909336 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 27 Dec 2022 17:57:27 +0100
Subject: [PATCH 02/15] use weakref

---
 sklearn/_config.py     | 13 +++++++------
 sklearn/utils/fixes.py |  8 ++++----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index b59922d366acc..07b471b16b9b8 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -3,6 +3,7 @@
 import os
 from contextlib import contextmanager as contextmanager
 import threading
+import weakref
 
 _global_config_default = {
     "assume_finite": bool(os.environ.get("SKLEARN_ASSUME_FINITE", False)),
@@ -17,7 +18,7 @@
     "transform_output": "default",
 }
 _threadlocal = threading.local()
-_thread_config = {}
+_thread_config = weakref.WeakKeyDictionary()  # type: ignore
 
 
 def _get_threadlocal_config():
@@ -29,11 +30,11 @@ def _get_threadlocal_config():
     """
     if not hasattr(_threadlocal, "global_config"):
         _threadlocal.global_config = _global_config_default.copy()
-        _thread_config[threading.get_ident()] = _threadlocal.global_config
+        _thread_config[threading.current_thread()] = _threadlocal.global_config
     return _threadlocal.global_config
 
 
-def get_config(thread_id=None):
+def get_config(thread=None):
     """Retrieve current values for configuration set by :func:`set_config`.
 
     Parameters
@@ -54,10 +55,10 @@ def get_config(thread_id=None):
     """
     # Return a copy of the threadlocal configuration so that users will
     # not be able to modify the configuration with the returned dict.
-    if thread_id is None:
+    if thread is None:
         return _get_threadlocal_config().copy()
-    _get_threadlocal_config()
-    return _thread_config[thread_id].copy()
+    _get_threadlocal_config()  # register the config to the thread if does not exist
+    return _thread_config[thread].copy()
 
 
 def set_config(
diff --git a/sklearn/utils/fixes.py b/sklearn/utils/fixes.py
index 811f4c30da72c..f7cd5189262fb 100644
--- a/sklearn/utils/fixes.py
+++ b/sklearn/utils/fixes.py
@@ -108,13 +108,13 @@ def _eigh(*args, **kwargs):
 
 
 # remove when https://github.com/joblib/joblib/issues/1071 is fixed
-def delayed(func, thread_id=threading.get_ident()):
+def delayed(func, thread=threading.current_thread()):
     """Decorator used to capture the arguments of a function."""
 
     def decorate(func):
         @functools.wraps(func)
         def wrapper(*args, **kwargs):
-            return _FuncWrapper(func, thread_id=thread_id), args, kwargs
+            return _FuncWrapper(func, thread=thread), args, kwargs
 
         return wrapper
 
@@ -124,9 +124,9 @@ def wrapper(*args, **kwargs):
 class _FuncWrapper:
     """ "Load the global configuration before calling the function."""
 
-    def __init__(self, function, thread_id=None):
+    def __init__(self, function, thread):
         self.function = function
-        self.config = get_config(thread_id=thread_id)
+        self.config = get_config(thread=thread)
         update_wrapper(self, self.function)
 
     def __call__(self, *args, **kwargs):

From 2d4e553e1d0054672fe927d6d8cb28bb8f95da7b Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 27 Dec 2022 18:00:43 +0100
Subject: [PATCH 03/15] doc stuff

---
 sklearn/_config.py | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index 07b471b16b9b8..0222b21d7f8ca 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -25,8 +25,8 @@ def _get_threadlocal_config():
     """Get a threadlocal **mutable** configuration.
 
     If the configuration does not exist, copy the default global configuration.
-    The configuration is also registered to in a global dictionary where the
-    key is the thread id.
+    The configuration is also registered to a global dictionary where the keys
+    are weak references to the thread objects.
     """
     if not hasattr(_threadlocal, "global_config"):
         _threadlocal.global_config = _global_config_default.copy()
@@ -39,9 +39,9 @@ def get_config(thread=None):
 
     Parameters
     ----------
-    thread_id : int, default=None
-        The thread id from which to retrieve the configuration. If `None`,
-        the current thread id is used.
+    thread : Thread, default=None
+        The thread for which to retrieve the configuration. If None, the
+        configuration of the current thread is returned.
 
     Returns
     -------
@@ -55,9 +55,9 @@ def get_config(thread=None):
     """
     # Return a copy of the threadlocal configuration so that users will
     # not be able to modify the configuration with the returned dict.
+    threadlocal_config = _get_threadlocal_config()
     if thread is None:
-        return _get_threadlocal_config().copy()
-    _get_threadlocal_config()  # register the config to the thread if does not exist
+        return threadlocal_config.copy()
     return _thread_config[thread].copy()
 
 

From 3c03261112973ca056e1251e80f135a7b5dc2566 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 27 Dec 2022 18:18:27 +0100
Subject: [PATCH 04/15] TST add test for delayed

---
 sklearn/utils/tests/test_fixes.py | 41 +++++++++++++++++++++++++++++--
 1 file changed, 39 insertions(+), 2 deletions(-)

diff --git a/sklearn/utils/tests/test_fixes.py b/sklearn/utils/tests/test_fixes.py
index 3566897da5efc..c4c579257086b 100644
--- a/sklearn/utils/tests/test_fixes.py
+++ b/sklearn/utils/tests/test_fixes.py
@@ -4,15 +4,18 @@
 # License: BSD 3 clause
 
 import math
+import threading
 
 import numpy as np
 import pytest
 import scipy.stats
 
+from joblib import Parallel
+
+import sklearn
 from sklearn.utils._testing import assert_array_equal
 
-from sklearn.utils.fixes import _object_dtype_isnan
-from sklearn.utils.fixes import loguniform
+from sklearn.utils.fixes import _object_dtype_isnan, delayed, loguniform
 
 
 @pytest.mark.parametrize("dtype, val", ([object, 1], [object, "a"], [float, 1]))
@@ -46,3 +49,37 @@ def test_loguniform(low, high, base):
     assert loguniform(base**low, base**high).rvs(random_state=0) == loguniform(
         base**low, base**high
     ).rvs(random_state=0)
+
+
+def test_delayed_fetching_right_config():
+    """Check that `delayed` function fetches the right config associated to
+    the main thread.
+
+    Non-regression test for:
+    https://github.com/scikit-learn/scikit-learn/issues/25239
+    """
+
+    def get_working_memory():
+        return sklearn.get_config()["working_memory"]
+
+    n_iter = 10
+
+    # by default, we register the main thread and we should retrieve the
+    # parameters defined within the context manager
+    with sklearn.config_context(working_memory=123):
+        results = Parallel(n_jobs=2, pre_dispatch=4)(
+            delayed(get_working_memory)() for _ in range(n_iter)
+        )
+
+    assert results == [123] * n_iter
+
+    # simulate that we refer to another thread
+    local_thread = threading.Thread(target=sklearn.get_config)
+    local_thread.start()
+    local_thread.join()
+    with sklearn.config_context(working_memory=123):
+        results = Parallel(n_jobs=2, pre_dispatch=4)(
+            delayed(get_working_memory, thread=local_thread)() for _ in range(n_iter)
+        )
+
+    assert results == [get_working_memory()] * n_iter

From cd38957bd198b92286f79baa8384b9f47c648697 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 28 Dec 2022 10:31:51 +0100
Subject: [PATCH 05/15] TST add more test in config

---
 sklearn/tests/test_config.py | 43 ++++++++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/sklearn/tests/test_config.py b/sklearn/tests/test_config.py
index a0b8f29662b69..e84ffbec54d8e 100644
--- a/sklearn/tests/test_config.py
+++ b/sklearn/tests/test_config.py
@@ -1,4 +1,5 @@
 import time
+import threading
 from concurrent.futures import ThreadPoolExecutor
 
 from joblib import Parallel
@@ -120,15 +121,15 @@ def test_config_threadsafe_joblib(backend):
     should be the same as the value passed to the function. In other words,
     it is not influenced by the other job setting assume_finite to True.
     """
-    assume_finites = [False, True]
-    sleep_durations = [0.1, 0.2]
+    assume_finites = [False, True, False, True]
+    sleep_durations = [0.1, 0.2, 0.1, 0.2]
 
-    items = Parallel(backend=backend, n_jobs=2)(
+    items = Parallel(backend=backend, n_jobs=2, pre_dispatch=2)(
         delayed(set_assume_finite)(assume_finite, sleep_dur)
         for assume_finite, sleep_dur in zip(assume_finites, sleep_durations)
     )
 
-    assert items == [False, True]
+    assert items == [False, True, False, True]
 
 
 def test_config_threadsafe():
@@ -136,8 +137,8 @@ def test_config_threadsafe():
     between threads. Same test as `test_config_threadsafe_joblib` but with
     `ThreadPoolExecutor`."""
 
-    assume_finites = [False, True]
-    sleep_durations = [0.1, 0.2]
+    assume_finites = [False, True, False, True]
+    sleep_durations = [0.1, 0.2, 0.1, 0.2]
 
     with ThreadPoolExecutor(max_workers=2) as e:
         items = [
@@ -145,4 +146,32 @@ def test_config_threadsafe():
             for output in e.map(set_assume_finite, assume_finites, sleep_durations)
         ]
 
-    assert items == [False, True]
+    assert items == [False, True, False, True]
+
+
+def test_get_config_thread_dependent():
+    """Check that we can retrieve the config file from a specific thread."""
+
+    def set_definitive_assume_finite(assume_finite, sleep_duration):
+        set_config(assume_finite=assume_finite)
+        time.sleep(sleep_duration)
+        return get_config()["assume_finite"]
+
+    thread = threading.Thread(target=set_definitive_assume_finite, args=(True, 0.1))
+    thread.start()
+    thread.join()
+
+    thread_specific_config = get_config(thread=thread)
+    assert thread_specific_config["assume_finite"] is True
+    main_thread_config = get_config()
+    assert main_thread_config["assume_finite"] is False
+
+    # check that we have 2 threads registered in the thread config dictionary
+    from sklearn._config import _thread_config
+
+    assert len(_thread_config) == 2
+
+    # delete the thread and check that the dictionary does keep a reference to it
+    # since we use a weakref dictionary
+    del thread
+    assert len(_thread_config) == 1

From 37ce3efb456e082b165b54e8854677612e02a382 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 28 Dec 2022 10:39:39 +0100
Subject: [PATCH 06/15] DOC add a changelog entry

---
 doc/whats_new/v1.2.rst | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/doc/whats_new/v1.2.rst b/doc/whats_new/v1.2.rst
index 6442979db402e..fdaa22798ae9c 100644
--- a/doc/whats_new/v1.2.rst
+++ b/doc/whats_new/v1.2.rst
@@ -9,9 +9,24 @@ Version 1.2.1
 
 **In Development**
 
+Changes impacting all modules
+-----------------------------
+
+- |Fix| Fix a bug that was ignoring the global configuration in estimators using
+  `n_jobs > 1`. This bug was triggered for the tasks not dispatch by the main
+  thread in `joblib` since :func:`sklearn.get_config` uses thread local configuration.
+  :pr:`25242` by :user:`Guillaume Lemaitre <glemaitre>`.
+
 Changelog
 ---------
 
+:mod:`sklearn`
+..............
+
+- |Enhancement| :func:`sklearn.get_config` takes a parameter `thread` allowing to
+  retrieve the local configuration of this specific `thread`.
+  :pr:`25242` by :user:`Guillaume Lemaitre <glemaitre>`.
+
 :mod:`sklearn.base`
 ...................
 

From 011a7ecd935b7deb7dd534204a268c11fdd8933a Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 28 Dec 2022 10:52:06 +0100
Subject: [PATCH 07/15] be nice with mypy

---
 sklearn/_config.py | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index 0222b21d7f8ca..1e0773501a5e5 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -1,9 +1,11 @@
 """Global configuration state and functions for management
 """
 import os
-from contextlib import contextmanager as contextmanager
 import threading
-import weakref
+
+from contextlib import contextmanager as contextmanager
+from typing import Dict
+from weakref import WeakKeyDictionary
 
 _global_config_default = {
     "assume_finite": bool(os.environ.get("SKLEARN_ASSUME_FINITE", False)),
@@ -18,7 +20,7 @@
     "transform_output": "default",
 }
 _threadlocal = threading.local()
-_thread_config = weakref.WeakKeyDictionary()  # type: ignore
+_thread_config = WeakKeyDictionary()  # type: WeakKeyDictionary[threading.Thread, Dict]
 
 
 def _get_threadlocal_config():

From 67a9f186ffcee1740602ba4ed68f78db9d37ec83 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 28 Dec 2022 10:57:55 +0100
Subject: [PATCH 08/15] avoid flake8 complain

---
 sklearn/_config.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index 1e0773501a5e5..6764b739a5d46 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -4,7 +4,7 @@
 import threading
 
 from contextlib import contextmanager as contextmanager
-from typing import Dict
+from typing import Dict  # noqa
 from weakref import WeakKeyDictionary
 
 _global_config_default = {

From e139fa71d771e2c27c4216c7df7874bc3494c565 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 28 Dec 2022 11:25:00 +0100
Subject: [PATCH 09/15] remove test that can fail with parallel execution

---
 sklearn/tests/test_config.py | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/sklearn/tests/test_config.py b/sklearn/tests/test_config.py
index e84ffbec54d8e..389512c742e30 100644
--- a/sklearn/tests/test_config.py
+++ b/sklearn/tests/test_config.py
@@ -165,13 +165,3 @@ def set_definitive_assume_finite(assume_finite, sleep_duration):
     assert thread_specific_config["assume_finite"] is True
     main_thread_config = get_config()
     assert main_thread_config["assume_finite"] is False
-
-    # check that we have 2 threads registered in the thread config dictionary
-    from sklearn._config import _thread_config
-
-    assert len(_thread_config) == 2
-
-    # delete the thread and check that the dictionary does keep a reference to it
-    # since we use a weakref dictionary
-    del thread
-    assert len(_thread_config) == 1

From cf16195a53a42cc2dc72d9e5bc67127ce85f1db1 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 3 Jan 2023 09:52:18 +0100
Subject: [PATCH 10/15] add thread argument to private function

---
 sklearn/utils/fixes.py            | 7 ++++++-
 sklearn/utils/tests/test_fixes.py | 8 ++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/sklearn/utils/fixes.py b/sklearn/utils/fixes.py
index f7cd5189262fb..69a18476a412e 100644
--- a/sklearn/utils/fixes.py
+++ b/sklearn/utils/fixes.py
@@ -108,8 +108,13 @@ def _eigh(*args, **kwargs):
 
 
 # remove when https://github.com/joblib/joblib/issues/1071 is fixed
-def delayed(func, thread=threading.current_thread()):
+def delayed(func):
     """Decorator used to capture the arguments of a function."""
+    return _delayed(func)
+
+
+def _delayed(func, thread=threading.current_thread()):
+    """Private function to expose the thread argument."""
 
     def decorate(func):
         @functools.wraps(func)
diff --git a/sklearn/utils/tests/test_fixes.py b/sklearn/utils/tests/test_fixes.py
index c4c579257086b..ccf8c94a5d35d 100644
--- a/sklearn/utils/tests/test_fixes.py
+++ b/sklearn/utils/tests/test_fixes.py
@@ -15,7 +15,7 @@
 import sklearn
 from sklearn.utils._testing import assert_array_equal
 
-from sklearn.utils.fixes import _object_dtype_isnan, delayed, loguniform
+from sklearn.utils.fixes import _delayed, _object_dtype_isnan, loguniform
 
 
 @pytest.mark.parametrize("dtype, val", ([object, 1], [object, "a"], [float, 1]))
@@ -52,7 +52,7 @@ def test_loguniform(low, high, base):
 
 
 def test_delayed_fetching_right_config():
-    """Check that `delayed` function fetches the right config associated to
+    """Check that `_delayed` function fetches the right config associated to
     the main thread.
 
     Non-regression test for:
@@ -68,7 +68,7 @@ def get_working_memory():
     # parameters defined within the context manager
     with sklearn.config_context(working_memory=123):
         results = Parallel(n_jobs=2, pre_dispatch=4)(
-            delayed(get_working_memory)() for _ in range(n_iter)
+            _delayed(get_working_memory)() for _ in range(n_iter)
         )
 
     assert results == [123] * n_iter
@@ -79,7 +79,7 @@ def get_working_memory():
     local_thread.join()
     with sklearn.config_context(working_memory=123):
         results = Parallel(n_jobs=2, pre_dispatch=4)(
-            delayed(get_working_memory, thread=local_thread)() for _ in range(n_iter)
+            _delayed(get_working_memory, thread=local_thread)() for _ in range(n_iter)
         )
 
     assert results == [get_working_memory()] * n_iter

From 52bf297596edd5d2df5e7d3e6ba5cb9e543f9740 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 3 Jan 2023 09:59:26 +0100
Subject: [PATCH 11/15] MAINT remove threadlocal

---
 sklearn/_config.py | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index 6764b739a5d46..4841b20e2e812 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -19,21 +19,22 @@
     "array_api_dispatch": False,
     "transform_output": "default",
 }
-_threadlocal = threading.local()
 _thread_config = WeakKeyDictionary()  # type: WeakKeyDictionary[threading.Thread, Dict]
 
 
-def _get_threadlocal_config():
-    """Get a threadlocal **mutable** configuration.
+def _get_thread_config(thread=None):
+    """Get a thread **mutable** configuration.
 
     If the configuration does not exist, copy the default global configuration.
     The configuration is also registered to a global dictionary where the keys
     are weak references to the thread objects.
     """
-    if not hasattr(_threadlocal, "global_config"):
-        _threadlocal.global_config = _global_config_default.copy()
-        _thread_config[threading.current_thread()] = _threadlocal.global_config
-    return _threadlocal.global_config
+    if thread is None:
+        thread = threading.current_thread()
+
+    if thread not in _thread_config:
+        _thread_config[thread] = _global_config_default.copy()
+    return _thread_config[thread]
 
 
 def get_config(thread=None):
@@ -55,12 +56,9 @@ def get_config(thread=None):
     config_context : Context manager for global scikit-learn configuration.
     set_config : Set global scikit-learn configuration.
     """
-    # Return a copy of the threadlocal configuration so that users will
-    # not be able to modify the configuration with the returned dict.
-    threadlocal_config = _get_threadlocal_config()
-    if thread is None:
-        return threadlocal_config.copy()
-    return _thread_config[thread].copy()
+    # Return a copy of the configuration so that users will not be able to
+    # modify the configuration with the returned dict.
+    return _get_thread_config(thread=thread).copy()
 
 
 def set_config(
@@ -157,7 +155,7 @@ def set_config(
     config_context : Context manager for global scikit-learn configuration.
     get_config : Retrieve current values of the global configuration.
     """
-    local_config = _get_threadlocal_config()
+    local_config = _get_thread_config()
 
     if assume_finite is not None:
         local_config["assume_finite"] = assume_finite

From 566560300fd8ad80c76a6e4b5b99472219ab32c7 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Tue, 3 Jan 2023 10:06:24 +0100
Subject: [PATCH 12/15] do not modify the API of get_config

---
 sklearn/_config.py           | 10 ++--------
 sklearn/tests/test_config.py | 10 ++++++----
 sklearn/utils/fixes.py       |  4 ++--
 3 files changed, 10 insertions(+), 14 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index 4841b20e2e812..2069a22b0ff76 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -37,15 +37,9 @@ def _get_thread_config(thread=None):
     return _thread_config[thread]
 
 
-def get_config(thread=None):
+def get_config():
     """Retrieve current values for configuration set by :func:`set_config`.
 
-    Parameters
-    ----------
-    thread : Thread, default=None
-        The thread for which to retrieve the configuration. If None, the
-        configuration of the current thread is returned.
-
     Returns
     -------
     config : dict
@@ -58,7 +52,7 @@ def get_config(thread=None):
     """
     # Return a copy of the configuration so that users will not be able to
     # modify the configuration with the returned dict.
-    return _get_thread_config(thread=thread).copy()
+    return _get_thread_config().copy()
 
 
 def set_config(
diff --git a/sklearn/tests/test_config.py b/sklearn/tests/test_config.py
index 389512c742e30..ad7d41f2f81db 100644
--- a/sklearn/tests/test_config.py
+++ b/sklearn/tests/test_config.py
@@ -5,6 +5,8 @@
 from joblib import Parallel
 import pytest
 
+from sklearn._config import _get_thread_config
+
 from sklearn import get_config, set_config, config_context
 from sklearn.utils.fixes import delayed
 
@@ -149,19 +151,19 @@ def test_config_threadsafe():
     assert items == [False, True, False, True]
 
 
-def test_get_config_thread_dependent():
+def test_get_thread_config():
     """Check that we can retrieve the config file from a specific thread."""
 
     def set_definitive_assume_finite(assume_finite, sleep_duration):
         set_config(assume_finite=assume_finite)
         time.sleep(sleep_duration)
-        return get_config()["assume_finite"]
+        return _get_thread_config()["assume_finite"]
 
     thread = threading.Thread(target=set_definitive_assume_finite, args=(True, 0.1))
     thread.start()
     thread.join()
 
-    thread_specific_config = get_config(thread=thread)
+    thread_specific_config = _get_thread_config(thread=thread)
     assert thread_specific_config["assume_finite"] is True
-    main_thread_config = get_config()
+    main_thread_config = _get_thread_config()
     assert main_thread_config["assume_finite"] is False
diff --git a/sklearn/utils/fixes.py b/sklearn/utils/fixes.py
index 69a18476a412e..285b306f3fe74 100644
--- a/sklearn/utils/fixes.py
+++ b/sklearn/utils/fixes.py
@@ -21,7 +21,7 @@
 import scipy
 import scipy.stats
 import threadpoolctl
-from .._config import config_context, get_config
+from .._config import config_context, _get_thread_config
 from ..externals._packaging.version import parse as parse_version
 
 
@@ -131,7 +131,7 @@ class _FuncWrapper:
 
     def __init__(self, function, thread):
         self.function = function
-        self.config = get_config(thread=thread)
+        self.config = _get_thread_config(thread=thread)
         update_wrapper(self, self.function)
 
     def __call__(self, *args, **kwargs):

From e42793f293201db3baf51553143880bd0050c343 Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 4 Jan 2023 11:52:00 +0100
Subject: [PATCH 13/15] Apply suggestions from code review

Co-authored-by: Thomas J. Fan <thomasjpfan@gmail.com>
---
 sklearn/_config.py           | 2 +-
 sklearn/tests/test_config.py | 9 ++-------
 2 files changed, 3 insertions(+), 8 deletions(-)

diff --git a/sklearn/_config.py b/sklearn/_config.py
index 2069a22b0ff76..0f5f51ff20bc0 100644
--- a/sklearn/_config.py
+++ b/sklearn/_config.py
@@ -3,7 +3,7 @@
 import os
 import threading
 
-from contextlib import contextmanager as contextmanager
+from contextlib import contextmanager
 from typing import Dict  # noqa
 from weakref import WeakKeyDictionary
 
diff --git a/sklearn/tests/test_config.py b/sklearn/tests/test_config.py
index ad7d41f2f81db..e9248bcac34b1 100644
--- a/sklearn/tests/test_config.py
+++ b/sklearn/tests/test_config.py
@@ -152,14 +152,9 @@ def test_config_threadsafe():
 
 
 def test_get_thread_config():
-    """Check that we can retrieve the config file from a specific thread."""
+    """Check that we can retrieve the config from a specific thread."""
 
-    def set_definitive_assume_finite(assume_finite, sleep_duration):
-        set_config(assume_finite=assume_finite)
-        time.sleep(sleep_duration)
-        return _get_thread_config()["assume_finite"]
-
-    thread = threading.Thread(target=set_definitive_assume_finite, args=(True, 0.1))
+    thread = threading.Thread(target=set_config, kwargs={"assume_finite": True})
     thread.start()
     thread.join()
 

From bb2b40dcd93e1ef2ad9e50f35d59dbce0f02f5fe Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 4 Jan 2023 11:52:27 +0100
Subject: [PATCH 14/15] DOC update changelog

---
 doc/whats_new/v1.2.rst | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/doc/whats_new/v1.2.rst b/doc/whats_new/v1.2.rst
index ccfc325c28fef..f67852a8c0b8c 100644
--- a/doc/whats_new/v1.2.rst
+++ b/doc/whats_new/v1.2.rst
@@ -13,20 +13,13 @@ Changes impacting all modules
 -----------------------------
 
 - |Fix| Fix a bug that was ignoring the global configuration in estimators using
-  `n_jobs > 1`. This bug was triggered for the tasks not dispatch by the main
+  `n_jobs > 1`. This bug was triggered for the tasks not dispatched by the main
   thread in `joblib` since :func:`sklearn.get_config` uses thread local configuration.
   :pr:`25242` by :user:`Guillaume Lemaitre <glemaitre>`.
 
 Changelog
 ---------
 
-:mod:`sklearn`
-..............
-
-- |Enhancement| :func:`sklearn.get_config` takes a parameter `thread` allowing to
-  retrieve the local configuration of this specific `thread`.
-  :pr:`25242` by :user:`Guillaume Lemaitre <glemaitre>`.
-
 :mod:`sklearn.base`
 ...................
 

From 379249e921048bc030163ee78a0ce64bc7b433be Mon Sep 17 00:00:00 2001
From: Guillaume Lemaitre <g.lemaitre58@gmail.com>
Date: Wed, 4 Jan 2023 13:44:23 +0100
Subject: [PATCH 15/15] Update doc/whats_new/v1.2.rst

Co-authored-by: Olivier Grisel <olivier.grisel@ensta.org>
---
 doc/whats_new/v1.2.rst | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/doc/whats_new/v1.2.rst b/doc/whats_new/v1.2.rst
index f67852a8c0b8c..ec91071681af2 100644
--- a/doc/whats_new/v1.2.rst
+++ b/doc/whats_new/v1.2.rst
@@ -12,9 +12,11 @@ Version 1.2.1
 Changes impacting all modules
 -----------------------------
 
-- |Fix| Fix a bug that was ignoring the global configuration in estimators using
-  `n_jobs > 1`. This bug was triggered for the tasks not dispatched by the main
-  thread in `joblib` since :func:`sklearn.get_config` uses thread local configuration.
+- |Fix| Fix a bug where the current configuration was ignored in estimators using
+  `n_jobs > 1`. This bug was triggered for tasks dispatched by the ancillary
+  thread of `joblib` as :func:`sklearn.get_config` used to access an empty thread
+  local configuration instead of the configuration visible from the thread where
+  `delayed` was first called.
   :pr:`25242` by :user:`Guillaume Lemaitre <glemaitre>`.
 
 Changelog