From 7b7ad27fafe89042f3317046a69e6f89dc2e7f33 Mon Sep 17 00:00:00 2001
From: James Lamb <jaylamb20@gmail.com>
Date: Sun, 15 Aug 2021 16:20:40 -0500
Subject: [PATCH 1/2] [python] add type hints to logging functions in basic.py

---
 python-package/lightgbm/basic.py | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/python-package/lightgbm/basic.py b/python-package/lightgbm/basic.py
index de408a4be4db..3ae31f87f6a0 100644
--- a/python-package/lightgbm/basic.py
+++ b/python-package/lightgbm/basic.py
@@ -12,7 +12,7 @@
 from os.path import getsize
 from pathlib import Path
 from tempfile import NamedTemporaryFile
-from typing import Any, Dict, Iterable, List, Optional, Set, Tuple, Union
+from typing import Any, Callable, Dict, Iterable, List, Optional, Set, Tuple, Union
 
 import numpy as np
 import scipy.sparse
@@ -34,17 +34,17 @@ def _get_sample_count(total_nrow: int, params: str):
 
 
 class _DummyLogger:
-    def info(self, msg):
+    def info(self, msg: str) -> None:
         print(msg)
 
-    def warning(self, msg):
+    def warning(self, msg: str) -> None:
         warnings.warn(msg, stacklevel=3)
 
 
-_LOGGER = _DummyLogger()
+_LOGGER: Union[_DummyLogger, Logger] = _DummyLogger()
 
 
-def register_logger(logger):
+def register_logger(logger: Logger) -> None:
     """Register custom logger.
 
     Parameters
@@ -58,9 +58,9 @@ def register_logger(logger):
     _LOGGER = logger
 
 
-def _normalize_native_string(func):
+def _normalize_native_string(func: Callable[[str], None]) -> Callable[[str], None]:
     """Join log messages from native library which come by chunks."""
-    msg_normalized = []
+    msg_normalized: List[str] = []
 
     @wraps(func)
     def wrapper(msg):
@@ -75,20 +75,20 @@ def wrapper(msg):
     return wrapper
 
 
-def _log_info(msg):
+def _log_info(msg: str) -> None:
     _LOGGER.info(msg)
 
 
-def _log_warning(msg):
+def _log_warning(msg: str) -> None:
     _LOGGER.warning(msg)
 
 
 @_normalize_native_string
-def _log_native(msg):
+def _log_native(msg: str) -> None:
     _LOGGER.info(msg)
 
 
-def _log_callback(msg):
+def _log_callback(msg: bytes) -> None:
     """Redirect logs from native library into Python."""
     _log_native(str(msg.decode('utf-8')))
 

From a1bec4ed1b1cd99290996dd7f4435855c14abb37 Mon Sep 17 00:00:00 2001
From: James Lamb <jaylamb20@gmail.com>
Date: Tue, 17 Aug 2021 22:23:15 -0500
Subject: [PATCH 2/2] add hints on wrapper

---
 python-package/lightgbm/basic.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/python-package/lightgbm/basic.py b/python-package/lightgbm/basic.py
index 3ae31f87f6a0..5d8efb950f00 100644
--- a/python-package/lightgbm/basic.py
+++ b/python-package/lightgbm/basic.py
@@ -63,7 +63,7 @@ def _normalize_native_string(func: Callable[[str], None]) -> Callable[[str], Non
     msg_normalized: List[str] = []
 
     @wraps(func)
-    def wrapper(msg):
+    def wrapper(msg: str) -> None:
         nonlocal msg_normalized
         if msg.strip() == '':
             msg = ''.join(msg_normalized)