From 3a9ca873c7fc16558506b1af341c73eb8371c56e Mon Sep 17 00:00:00 2001
From: KotlinIsland <kotlinisland@users.noreply.github.com>
Date: Thu, 9 Feb 2023 15:59:49 +1000
Subject: [PATCH 1/2] blackd: fix issue for mishandling single character input

---
 CHANGES.md             | 2 ++
 src/blackd/__init__.py | 3 ++-
 tests/test_blackd.py   | 6 ++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index c7ecc396214..1264294a828 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -41,6 +41,8 @@
 
 <!-- Changes to blackd -->
 
+- fix a bug where a single character would cause a 500 (#3558)
+
 ### Integrations
 
 <!-- For example, Docker, GitHub Actions, pre-commit, editors -->
diff --git a/src/blackd/__init__.py b/src/blackd/__init__.py
index ba4750b8298..e478c276a5f 100644
--- a/src/blackd/__init__.py
+++ b/src/blackd/__init__.py
@@ -146,7 +146,8 @@ async def handle(request: web.Request, executor: Executor) -> web.Response:
         )
 
         # Preserve CRLF line endings
-        if req_str[req_str.find("\n") - 1] == "\r":
+        nl = req_str.find("\n")
+        if nl > 0 and req_str[nl - 1] == "\r":
             formatted_str = formatted_str.replace("\n", "\r\n")
             # If, after swapping line endings, nothing changed, then say so
             if formatted_str == req_str:
diff --git a/tests/test_blackd.py b/tests/test_blackd.py
index 5b6461f7685..85408326f80 100644
--- a/tests/test_blackd.py
+++ b/tests/test_blackd.py
@@ -240,3 +240,9 @@ async def test_normalizes_line_endings(self) -> None:
             response = await self.client.post("/", data=data)
             self.assertEqual(await response.text(), expected)
             self.assertEqual(response.status, 200)
+
+    @unittest_run_loop
+    async def test_single_character(self) -> None:
+        response = await self.client.post("/", data="1")
+        self.assertEqual(await response.text(), "1\n")
+        self.assertEqual(response.status, 200)

From 3629df9f1d99e9597b51558d0628f8d9de313cab Mon Sep 17 00:00:00 2001
From: Shantanu <12621235+hauntsaninja@users.noreply.github.com>
Date: Thu, 7 Sep 2023 00:01:45 -0700
Subject: [PATCH 2/2] Update CHANGES.md

---
 CHANGES.md | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/CHANGES.md b/CHANGES.md
index ad803537040..af2364d5eb3 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -43,7 +43,7 @@
 
 <!-- Changes to blackd -->
 
-- fix a bug where a single character would cause a 500 (#3558)
+- Fix an issue in `blackd` with single character input (#3558)
 
 ### Integrations