Empty vss.url is documented as disabled but aborts startup

[Kewe63]

Summary

The sample configuration says that an empty [vss].url disables VSS, but the startup argument resolver preserves the empty string and validates it as a URL. A daemon started with the documented value exits before startup.

Affected commit / version

• Commit: af03c7f1a65135a429f05a5820600338215954dc
• Package version: 0.1.0
• Branch: dev

Environment

• Linux (WSL2)
• rustc 1.94.0
• cargo 1.94.0
• No network or daemon service was used

Expected behavior

Given the sample contract:

[vss]
url = ""

VSS should remain disabled and startup argument resolution should succeed.

Actual behavior

The empty string remains Some("") and is rejected by validate_vss_url:

Error: Invalid VSS configuration: VSS URL `` must start with http:// or https://

Minimal local regression test

#[test]
fn empty_vss_url_disables_vss() {
    let ua = resolve(&base(&[]), "[vss]\nurl = \"\"\n").unwrap();
    assert!(ua.vss_url.is_none());
}

Exact command and output

cargo +1.94.0 test --locked --lib \
  args::tests::empty_vss_url_disables_vss -- --exact --test-threads=1

running 1 test
... FAILED
InvalidVssConfig("VSS URL `` must start with http:// or https://")

A release binary invoked with a temporary storage directory and this config also exited 1 with the same error.

Root cause

• Sample contract:

  rgb-lightning-node/sample-config.toml

  Lines 126 to 128 in af03c7f

  	[vss]
  	# VSS server URL for cloud backup (empty = VSS disabled)
  	#url = ""

• Resolution/validation:

  rgb-lightning-node/src/args.rs

  Lines 262 to 269 in af03c7f

  	let vss_url = args.vss_url.or(vss.url);
  	let vss_allow_http = args.vss_allow_http || vss.allow_http.unwrap_or(false);
  	let vss_allow_empty_restore =
  	args.vss_allow_empty_restore || vss.allow_empty_restore.unwrap_or(false);
  	// Reject http:// URLs unless the host is loopback or allow_http is set.
  	if let Some(url) = &vss_url {
  	crate::utils::validate_vss_url(url, vss_allow_http)?;
  	}

args.vss_url.or(vss.url) preserves Some(""), then validation treats it as a malformed URL instead of the documented disabled sentinel.

Concrete user impact

Uncommenting the documented sample value prevents the self-hosted daemon from starting instead of leaving VSS disabled.

Fork / upstream assessment

This configuration surface is UTEXO-specific and absent from the compared upstream master commit e4008278c80495ea8a8514580b899e771feff872.

Duplicate-check evidence and limitations

I searched open and closed UTEXO and upstream issues/PRs, issue comments, review comments, commit history, and current open PR path overlaps using the config key, exact error, empty/blank URL wording, and validator name. No matching report or fix was found. PRs #139 and #140 touch the same files but contain no VSS URL hunk. Private maintainer discussions are not visible.

Suggested fix direction

Normalize an empty (preferably trimmed-empty) config value to None before URL validation, and retain a focused startup/config regression test.