[gentoo-portage-dev] [PATCH] dispatch-conf: avoid symlink "File exists" error (535850)

[Zac Medico <zmedico@gentoo.org>]

Since commit f17448317166bfac42dc279b8795cd581c189582, an existing
symlink in /etc/config-archive could trigger a fatal "File exists"
error. Handle this by removing the destination file if it exists. This
was not necessary when dispatch-conf only supported regular files,
since shutil.copy2 would simply overwrite the regular destination file.

Fixes: f17448317166 ("dispatch-conf: symlink support for bug #485598")
X-Gentoo-Bug: 535850
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=535850
---
 pym/portage/dispatch_conf.py | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/pym/portage/dispatch_conf.py b/pym/portage/dispatch_conf.py
index b27e68b..7d55182 100644
--- a/pym/portage/dispatch_conf.py
+++ b/pym/portage/dispatch_conf.py
@@ -179,6 +179,12 @@ def rcs_archive(archive, curconf, newconf, mrgconf):
 	if curconf_st is not None and \
 		(stat.S_ISREG(curconf_st.st_mode) or
 		stat.S_ISLNK(curconf_st.st_mode)):
+		# Remove destination file in order to ensure that the following
+		# symlink or copy2 call won't fail (see bug #535850).
+		try:
+			os.unlink(archive)
+		except OSError:
+			pass
 		try:
 			if stat.S_ISLNK(curconf_st.st_mode):
 				os.symlink(os.readlink(curconf), archive)
@@ -208,6 +214,12 @@ def rcs_archive(archive, curconf, newconf, mrgconf):
 		if has_branch:
 			os.rename(archive, archive + '.dist')
 
+		# Remove destination file in order to ensure that the following
+		# symlink or copy2 call won't fail (see bug #535850).
+		try:
+			os.unlink(archive)
+		except OSError:
+			pass
 		try:
 			if stat.S_ISLNK(mystat.st_mode):
 				os.symlink(os.readlink(newconf), archive)
@@ -264,6 +276,12 @@ def file_archive(archive, curconf, newconf, mrgconf):
 	if curconf_st is not None and \
 		(stat.S_ISREG(curconf_st.st_mode) or
 		stat.S_ISLNK(curconf_st.st_mode)):
+		# Remove destination file in order to ensure that the following
+		# symlink or copy2 call won't fail (see bug #535850).
+		try:
+			os.unlink(archive)
+		except OSError:
+			pass
 		try:
 			if stat.S_ISLNK(curconf_st.st_mode):
 				os.symlink(os.readlink(curconf), archive)
@@ -285,6 +303,12 @@ def file_archive(archive, curconf, newconf, mrgconf):
 		stat.S_ISLNK(mystat.st_mode)):
 		# Save off new config file in the archive dir with .dist.new suffix
 		newconf_archive = archive + '.dist.new'
+		# Remove destination file in order to ensure that the following
+		# symlink or copy2 call won't fail (see bug #535850).
+		try:
+			os.unlink(newconf_archive)
+		except OSError:
+			pass
 		try:
 			if stat.S_ISLNK(mystat.st_mode):
 				os.symlink(os.readlink(newconf), newconf_archive)
-- 
2.0.5