MagnetUri uri field invariant vulnerability

[coderabbitai]

Description

The MagnetUri struct has a potential invariant issue with its uri field that could lead to serialization problems.

Problem

The uri field is marked with #[serde(skip)], which means:

• It defaults to an empty string during direct struct/map deserialization
• The Serialize implementation returns self.uri directly
• If uri is empty, serializing produces an empty string

While the custom deserialize implementation (lines 93-101) properly sets uri via try_from(), this protection is bypassed if MagnetUri is deserialized directly outside the MetaInfo enum wrapper.

This could be a problem if we export the torrent twice back to back, as the second export might serialize an empty URI.

Suggested Solutions

1. Recommended: Make struct fields private, expose through accessors, and require all construction via TryFrom/parse(). Add #[serde(deserialize_with = "Self::deserialize")] on the struct to prevent direct deserialization bypass.

2. Alternative: Add fallback URI reconstruction in serialize() when uri.is_empty().

References

• PR: feat: Exportable engine state #166
• Comment: feat: Exportable engine state #166 (comment)
• Requester: @artrixdotdev