make StringIO like other file objects in that readline(-1) has no effect #7348
diff --git a/Lib/StringIO.py b/Lib/StringIO.py
index 054ad4c..340fae1 100644
--- a/Lib/StringIO.py
+++ b/Lib/StringIO.py
@@ -158,7 +158,7 @@
newpos = self.len
else:
newpos = i+1
- if length is not None:
+ if length is not None and length > 0:
if self.pos + length < newpos:
newpos = self.pos + length
r = self.buf[self.pos:newpos]
diff --git a/Lib/test/test_StringIO.py b/Lib/test/test_StringIO.py
index f5a177e..d10255d 100644
--- a/Lib/test/test_StringIO.py
+++ b/Lib/test/test_StringIO.py
@@ -28,6 +28,8 @@
eq(self._fp.read(10), self._line[:10])
eq(self._fp.readline(), self._line[10:] + '\n')
eq(len(self._fp.readlines(60)), 2)
+ self._fp.seek(0)
+ eq(self._fp.readline(-1), self._line + '\n')
def test_writes(self):
f = self.MODULE.StringIO()