From adbe2337f5ba849bf6ff4f61794887b9c1944157 Mon Sep 17 00:00:00 2001
From: Jussi Timperi <236182+Ban3@users.noreply.github.com>
Date: Fri, 27 May 2022 18:11:53 +0300
Subject: [PATCH] fix(tone_convert): don't append tone number to empty input
 (#279)

---
 pypinyin/style/_tone_convert.py    | 2 +-
 tests/contrib/test_tone_convert.py | 2 ++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/pypinyin/style/_tone_convert.py b/pypinyin/style/_tone_convert.py
index cdbea82..244a302 100644
--- a/pypinyin/style/_tone_convert.py
+++ b/pypinyin/style/_tone_convert.py
@@ -545,7 +545,7 @@ def tone3_to_tone2(tone3, v_to_u=False):
 
 def _improve_tone3(tone3, neutral_tone_with_five=False):
     number = _get_number_from_pinyin(tone3)
-    if number is None and neutral_tone_with_five:
+    if number is None and neutral_tone_with_five and tone3 != '':
         tone3 = '{}5'.format(tone3)
     return tone3
 
diff --git a/tests/contrib/test_tone_convert.py b/tests/contrib/test_tone_convert.py
index f3bac25..67dcf58 100644
--- a/tests/contrib/test_tone_convert.py
+++ b/tests/contrib/test_tone_convert.py
@@ -118,6 +118,8 @@ def test_tone_tone3(pinyin, result):
 @mark.parametrize('pinyin,neutral_tone_with_five,result', [
     ['shang', False, 'shang'],
     ['shang', True, 'shang5'],
+    ['', False, ''],
+    ['', True, '']
 ])
 def test_tone_tone3_with_neutral_tone_with_five(
         pinyin, neutral_tone_with_five, result):