fetch: add force parameter (bug 697566)

Add a force parameter which forces download even when a file already
exists in DISTDIR (and no digests are available to verify it). This
avoids the need to remove the existing file in advance, which makes
it possible to atomically replace the file and avoid interference
with concurrent processes. This is useful when using FETCHCOMMAND to
fetch a mirror's layout.conf file, for the purposes of bug 697566.

Bug: https://bugs.gentoo.org/697566
Reviewed-by: Michał Górny <mgorny@gentoo.org>
Signed-off-by: Zac Medico <zmedico@gentoo.org>

1 files changed, 37 insertions, 3 deletions

diff --git a/lib/portage/tests/ebuild/test_fetch.py b/lib/portage/tests/ebuild/test_fetch.py
index f50fea0dd..538fb1754 100644
--- a/lib/portage/tests/ebuild/test_fetch.py
+++ b/lib/portage/tests/ebuild/test_fetch.py
@@ -119,10 +119,44 @@ class EbuildFetchTestCase(TestCase):
 				with open(foo_path, 'rb') as f:
 					self.assertNotEqual(f.read(), distfiles['foo'])
 
-				# Remove the stale file in order to forcefully update it.
-				os.unlink(foo_path)
+				# Use force=True to update the stale file.
+				self.assertTrue(bool(run_async(fetch, foo_uri, settings, try_mirrors=False, force=True)))
 
-				self.assertTrue(bool(run_async(fetch, foo_uri, settings, try_mirrors=False)))
+				with open(foo_path, 'rb') as f:
+					self.assertEqual(f.read(), distfiles['foo'])
+
+				# Test force=True with FEATURES=skiprocheck, using read-only DISTDIR.
+				# FETCHCOMMAND is set to temporarily chmod +w DISTDIR. Note that
+				# FETCHCOMMAND must perform atomic rename itself due to read-only
+				# DISTDIR.
+				with open(foo_path, 'wb') as f:
+					f.write(b'stale content\n')
+				orig_fetchcommand = settings['FETCHCOMMAND']
+				orig_distdir_mode = os.stat(settings['DISTDIR']).st_mode
+				temp_fetchcommand = os.path.join(eubin, 'fetchcommand')
+				with open(temp_fetchcommand, 'w') as f:
+					f.write("""
+					set -e
+					URI=$1
+					DISTDIR=$2
+					FILE=$3
+					trap 'chmod a-w "${DISTDIR}"' EXIT
+					chmod ug+w "${DISTDIR}"
+					%s
+					mv -f "${DISTDIR}/${FILE}.__download__" "${DISTDIR}/${FILE}"
+				""" % orig_fetchcommand.replace('${FILE}', '${FILE}.__download__'))
+				settings['FETCHCOMMAND'] = '"%s" "%s" "${URI}" "${DISTDIR}" "${FILE}"' % (BASH_BINARY, temp_fetchcommand)
+				settings.features.add('skiprocheck')
+				settings.features.remove('distlocks')
+				os.chmod(settings['DISTDIR'], 0o555)
+				try:
+					self.assertTrue(bool(run_async(fetch, foo_uri, settings, try_mirrors=False, force=True)))
+				finally:
+					settings['FETCHCOMMAND'] = orig_fetchcommand
+					os.chmod(settings['DISTDIR'], orig_distdir_mode)
+					settings.features.remove('skiprocheck')
+					settings.features.add('distlocks')
+					os.unlink(temp_fetchcommand)
 
 				with open(foo_path, 'rb') as f:
 					self.assertEqual(f.read(), distfiles['foo'])