[libvirt PATCH] scripts: Fix meson-install-symlink.py overwriting existing links

[Erik Skultety]

By default, symlink re-creation fails if the link already exists, more
specifically in case of meson-install-symlink.py:

Traceback (most recent call last):
  File "/<path_to_libvirt_repo>/scripts/meson-install-symlink.py",
    line 15, in <module>
        os.symlink(target, link)
FileExistsError: File exists: '../default.xml' -> 'default.xml'

Unfortunately, Python can't mimic "ln -sf", so we have to fix this
differently - create a temporary name which is then going to be used
for the temporary link followed by a rename with the original link's
name.
Note that this solution is racy as mktemp() doesn't guarantee
atomicity in link creation, so theoretically another process could come
and create a file with the same name as the temporary link name, but
a proper solution would be longer and not as elegant.

Signed-off-by: Erik Skultety <eskultet at redhat.com>
---
 scripts/meson-install-symlink.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/meson-install-symlink.py b/scripts/meson-install-symlink.py
index e38507072d..630dfc079f 100644
--- a/scripts/meson-install-symlink.py
+++ b/scripts/meson-install-symlink.py
@@ -2,6 +2,7 @@
 
 import os
 import sys
+import tempfile
 
 destdir = os.environ.get('DESTDIR', os.sep)
 dirname = sys.argv[1]
@@ -12,4 +13,7 @@ workdir = os.path.join(destdir, dirname.strip(os.sep))
 
 os.makedirs(workdir, exist_ok=True)
 os.chdir(workdir)
-os.symlink(target, link)
+
+templink = tempfile.mktemp(dir=workdir)
+os.symlink(target, templink)
+os.replace(templink, link)
-- 
2.26.2