collectstatic: do not crash on broken link (#56408)

tests/test_ctl.py

@@ -1,5 +1,6 @@
 import collections
 import os
+import shutil
 import sys
 from unittest import mock
 
@@ -63,7 +64,7 @@ def test_loading():
         cmd()
 
 
-def test_collectstatic(pub):
+def test_collectstatic(pub, tmp_path):
     CmdCollectStatic.collectstatic(pub)
     assert os.path.exists(os.path.join(pub.app_dir, 'collectstatic', 'css', 'required.png'))
     assert os.path.exists(os.path.join(pub.app_dir, 'collectstatic', 'js', 'qommon.forms.js'))
@@ -72,6 +73,20 @@ def test_collectstatic(pub):
     CmdCollectStatic.collectstatic(pub, clear=True, link=True)
     assert os.path.islink(os.path.join(pub.app_dir, 'collectstatic', 'css', 'required.png'))
 
+    # create a broken link
+    required_tmp = os.path.join(tmp_path, 'required.png')
+    required_link = os.path.join(pub.app_dir, 'collectstatic', 'css', 'required.png')
+    shutil.copy2(os.path.join(pub.app_dir, 'collectstatic', 'css', 'required.png'), required_tmp)
+    os.unlink(required_link)
+    os.symlink(required_tmp, required_link)
+    os.unlink(required_tmp)
+    # check that we have a broken link
+    assert os.path.islink(required_link) and not os.path.exists(required_link)
+    # still works if broken link exists
+    CmdCollectStatic.collectstatic(pub, link=True)
+    # link not broken any more
+    assert os.path.islink(required_link) and os.path.exists(required_link)
+
 
 def test_migrate(two_pubs):
     CmdMigrate().handle()

wcs/qommon/management/commands/collectstatic.py

@@ -78,7 +78,7 @@ class Command(BaseCommand):
                             continue
                         if not os.path.exists(dst_path):
                             os.makedirs(dst_path)
-                        if os.path.exists(dst_filename):
+                        if os.path.exists(dst_filename) or os.path.islink(dst_filename):
                             os.unlink(dst_filename)
                         if link:
                             os.symlink(src_filename, dst_filename)