From: Cody Maloney <cmaloney@users.noreply.github.com>
Date: Wed, 24 Jul 2024 06:14:35 +0000 (-0700)
Subject: GH-120754: Add more tests around seek + readall (#122103)
X-Git-Tag: v3.14.0a1~1007
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=9eb734111be90399fb6ae2f717d736abb8e518cb;p=thirdparty%2FPython%2Fcpython.git

GH-120754: Add more tests around seek + readall (#122103)

In the process of speeding up readall, A number of related tests
(ex. large file tests in test_zipfile) found problems with the
change I was making. This adds I/O tests to specifically test these
cases to help ensure they don't regress and hopefully make debugging
easier.

This is part of the improvements from
https://github.com/python/cpython/pull/121593#issuecomment-2222261986
---

diff --git a/Lib/test/test_largefile.py b/Lib/test/test_largefile.py
index 849b6cb3e50a..41f7b70e5cfe 100644
--- a/Lib/test/test_largefile.py
+++ b/Lib/test/test_largefile.py
@@ -141,6 +141,9 @@ class TestFileMethods(LargeFileTest):
             f.truncate(1)
             self.assertEqual(f.tell(), 0)       # else pointer moved
             f.seek(0)
+            # Verify readall on a truncated file is well behaved. read()
+            # without a size can be unbounded, this should get just the byte
+            # that remains.
             self.assertEqual(len(f.read()), 1)  # else wasn't truncated
 
     def test_seekable(self):
@@ -151,6 +154,22 @@ class TestFileMethods(LargeFileTest):
                 f.seek(pos)
                 self.assertTrue(f.seekable())
 
+    @bigmemtest(size=size, memuse=2, dry_run=False)
+    def test_seek_readall(self, _size):
+        # Seek which doesn't change position should readall successfully.
+        with self.open(TESTFN, 'rb') as f:
+            self.assertEqual(f.seek(0, os.SEEK_CUR), 0)
+            self.assertEqual(len(f.read()), size + 1)
+
+        # Seek which changes (or might change) position should readall
+        # successfully.
+        with self.open(TESTFN, 'rb') as f:
+            self.assertEqual(f.seek(20, os.SEEK_SET), 20)
+            self.assertEqual(len(f.read()), size - 19)
+
+        with self.open(TESTFN, 'rb') as f:
+            self.assertEqual(f.seek(-3, os.SEEK_END), size - 2)
+            self.assertEqual(len(f.read()), 3)
 
 def skip_no_disk_space(path, required):
     def decorator(fun):