Issue #6939: Fix file I/O objects in the `io` module to keep the original
file position when calling `truncate()`. It would previously change the
file position to the given argument, which goes against the tradition of
`ftruncate()` and other truncation APIs. Patch by Pascal Chambon.
diff --git a/Lib/io.py b/Lib/io.py
index 70f2aba..d090eec 100644
--- a/Lib/io.py
+++ b/Lib/io.py
@@ -880,7 +880,7 @@
elif pos < 0:
raise ValueError("negative truncate position %r" % (pos,))
del self._buffer[pos:]
- return self.seek(pos)
+ return pos
def readable(self):
return True
@@ -1215,8 +1215,7 @@
if pos is None:
pos = self.tell()
# Use seek to flush the read buffer.
- self.seek(pos)
- return BufferedWriter.truncate(self)
+ return BufferedWriter.truncate(self, pos)
def read(self, n=None):
if n is None:
@@ -1667,8 +1666,7 @@
self.flush()
if pos is None:
pos = self.tell()
- self.seek(pos)
- return self.buffer.truncate()
+ return self.buffer.truncate(pos)
def seek(self, cookie, whence=0):
if self.closed: