Ask when the preselected storage cannot hold the content

[MickLesk]

✍️ Description

i had issues after rebuild my hdd / ssd storages on my node2 (replaced and ordered).
the default.vars naming a storage that no longer takes vztmpl hangs the run.

🚀  Creating a InvoiceShelf LXC using the above default settings
  ✔️  Storage space validated
  💡   Preselected storage 'local' does not support content 'vztmpl' (or not found)
^C

Nothing is drawn and nothing exits. The cause:

while true; do
  if [[ -z "${var_template_storage:-}" ]]; then
    if select_storage template; then ...; break; fi
  fi
done

var_template_storage is non-empty exactly when default.vars supplied it, which is the only way to reach this branch — so the body never runs, select_storage is never called, and there is no break. It spins until Ctrl+C. The container branch has no loop, but it silently keeps the unusable value and fails later.

🔗 Related Issue

None filed — reported directly with the transcript above.

✅ Prerequisites (X in brackets)

• Self-review completed
• Tested thoroughly – see below
• No security risks
• API.txt regenerated – _storage_preselect_recover is internal; no loader snapshot changes

🧪 Testing

_storage_preselect_recover and _write_storage_to_vars extracted from the files, select_storage and whiptail stubbed, against a synthetic default.vars:

#	Check	Result
1	invalid preselect → asks, yes → key rewritten, no duplicate, other keys untouched	PASS
2	user declines → file untouched	PASS
3	no default.vars in play → selects, writes nothing, rc 0	PASS
4	nothing selectable → rc 1, caller exits instead of looping	PASS
5	chosen storage equals the stale one → no prompt, no write	PASS
6	key absent from the file → nothing added	PASS
7	the replaced loop, bounded to 3s → still spinning, never asks	PASS

Not run on a Proxmox host. bash -n passes on both files.

🛠️ Type of Change (X in brackets)

• 🐞 Bug fix

[github-actions]

Try this branch

The engine and the scripts resolve independently, so a production script can
be run against the engine from this PR by setting one variable:

COMMUNITY_SCRIPTS_CORE_URL=https://raw.githubusercontent.com/community-scripts/core/fix/storage-preselect-invalid \
bash -c "$(curl -fsSL https://raw.githubusercontent.com/community-scripts/ProxmoxVED/main/ct/debian.sh)"

Swap ct/debian.sh for whatever exercises the change.

This PR touches pve/, so it needs a Proxmox VE host.

Run a script from a fork as well

curl -fsSL https://raw.githubusercontent.com/community-scripts/core/fix/storage-preselect-invalid/tools/run.sh |
  bash -s -- https://raw.githubusercontent.com/YOU/ProxmoxVED/your-branch ct/debian.sh \
             https://raw.githubusercontent.com/community-scripts/core/fix/storage-preselect-invalid

Note that run.sh is reached through a pipe, so the script it starts inherits
an exhausted stdin. Whiptail is fine — it opens /dev/tty — but a plain read
would see EOF. The single-variable form above does not have that problem.

Useful flags while testing

dev_mode=net logs every engine fetch with status and duration, which is the
quickest way to confirm the branch is really being used. dev_mode=keep stops a
failed build from deleting the container along with the evidence.

[MickLesk]