From 1ecb57dd7dd516d3ecedf7e58ba84520281fbd00 Mon Sep 17 00:00:00 2001
From: Ben Li-Sauerwine <bsauerwine@gmail.com>
Date: Wed, 27 Jul 2022 03:26:26 -0400
Subject: [PATCH] Fix out of scope error when "dest" variable is undefined

Fixes #413 whereby the NamedTemporaryFile "dest" was out of scope in the
error handling portion of rewrite.

The problem was initially fixed in #414 but it got reverted because of a
linter error. This new commit works around that linter error.
---
 src/dotenv/main.py | 20 +++++++++-----------
 tests/test_main.py |  7 +++++++
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/dotenv/main.py b/src/dotenv/main.py
index 83ea3239..43248819 100644
--- a/src/dotenv/main.py
+++ b/src/dotenv/main.py
@@ -125,19 +125,17 @@ def rewrite(
     path: Union[str, os.PathLike],
     encoding: Optional[str],
 ) -> Iterator[Tuple[IO[str], IO[str]]]:
-    try:
-        if not os.path.isfile(path):
-            with open(path, "w+", encoding=encoding) as source:
-                source.write("")
-        with tempfile.NamedTemporaryFile(mode="w+", delete=False, encoding=encoding) as dest:
+    if not os.path.isfile(path):
+        with open(path, mode="w", encoding=encoding) as source:
+            source.write("")
+    with tempfile.NamedTemporaryFile(mode="w", encoding=encoding, delete=False) as dest:
+        try:
             with open(path, encoding=encoding) as source:
-                yield (source, dest)  # type: ignore
-    except BaseException:
-        if os.path.isfile(dest.name):
+                yield (source, dest)
+        except BaseException:
             os.unlink(dest.name)
-        raise
-    else:
-        shutil.move(dest.name, path)
+            raise
+    shutil.move(dest.name, path)
 
 
 def set_key(
diff --git a/tests/test_main.py b/tests/test_main.py
index 82c73ba1..9c895851 100644
--- a/tests/test_main.py
+++ b/tests/test_main.py
@@ -178,6 +178,13 @@ def test_unset_encoding(dotenv_file):
         assert f.read() == ""
 
 
+def test_set_key_unauthorized_file(dotenv_file):
+    os.chmod(dotenv_file, 0o000)
+
+    with pytest.raises(PermissionError):
+        dotenv.set_key(dotenv_file, "a", "x")
+
+
 def test_unset_non_existent_file(tmp_path):
     nx_file = str(tmp_path / "nx")
     logger = logging.getLogger("dotenv.main")