From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Wed, 8 Jul 2020 21:18:38 +0000 (-0700)
Subject: bpo-40597: Allow email.contextmanager set_content() to set a null string. (GH-20542)
X-Git-Tag: v3.8.4~8
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c1c50345933efca42169f03d79ff4fe3d9c06bdc;p=thirdparty%2FPython%2Fcpython.git

bpo-40597: Allow email.contextmanager set_content() to set a null string. (GH-20542)

(cherry picked from commit 4fa61a7732923f92de0f7830c12da48c4cec937f)

Co-authored-by: Mark Sapiro <mark@msapiro.net>
---

diff --git a/Lib/email/contentmanager.py b/Lib/email/contentmanager.py
index 2b4b8757f46f..b91fb0e5bca7 100644
--- a/Lib/email/contentmanager.py
+++ b/Lib/email/contentmanager.py
@@ -146,7 +146,7 @@ def _encode_text(string, charset, cte, policy):
     def normal_body(lines): return b'\n'.join(lines) + b'\n'
     if cte==None:
         # Use heuristics to decide on the "best" encoding.
-        if max(len(x) for x in lines) <= policy.max_line_length:
+        if max((len(x) for x in lines), default=0) <= policy.max_line_length:
             try:
                 return '7bit', normal_body(lines).decode('ascii')
             except UnicodeDecodeError:
diff --git a/Lib/test/test_email/test_contentmanager.py b/Lib/test/test_email/test_contentmanager.py
index 64dca2d017e6..f4f6bb715acd 100644
--- a/Lib/test/test_email/test_contentmanager.py
+++ b/Lib/test/test_email/test_contentmanager.py
@@ -303,6 +303,19 @@ class TestRawDataManager(TestEmailBase):
         self.assertEqual(m.get_payload(decode=True).decode('utf-8'), content)
         self.assertEqual(m.get_content(), content)
 
+    def test_set_text_plain_null(self):
+        m = self._make_message()
+        content = ''
+        raw_data_manager.set_content(m, content)
+        self.assertEqual(str(m), textwrap.dedent("""\
+            Content-Type: text/plain; charset="utf-8"
+            Content-Transfer-Encoding: 7bit
+
+
+            """))
+        self.assertEqual(m.get_payload(decode=True).decode('utf-8'), '\n')
+        self.assertEqual(m.get_content(), '\n')
+
     def test_set_text_html(self):
         m = self._make_message()
         content = "<p>Simple message.</p>\n"
diff --git a/Misc/NEWS.d/next/Library/2020-05-30-12-44-29.bpo-39384.Iqxy3q.rst b/Misc/NEWS.d/next/Library/2020-05-30-12-44-29.bpo-39384.Iqxy3q.rst
new file mode 100644
index 000000000000..482ae624da07
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2020-05-30-12-44-29.bpo-39384.Iqxy3q.rst
@@ -0,0 +1 @@
+Fixed email.contentmanager to allow set_content() to set a null string.