Enum PriorKeychainState 

enum PriorKeychainState {
    Existed(Zeroizing<String>),
    Absent,
    Unknown,
}

What a keychain entry held immediately before a write to it, so a later failure (the SQL write in muxbus_save, or a sibling field’s write in write_split_tokens) can be rolled back to that exact prior state. Three-way, not a bool: reagent P1 on #2260 caught a first version of this that collapsed Ok(None) (“genuinely no prior entry”) and Err (“the read itself failed, prior state UNKNOWN”) into the same None, so an unrelated transient read failure would make the rollback branch delete a real, valid, previously-stored credential it simply couldn’t read — turning a transient glitch into a forced full re-login. Unknown gets neither restore nor delete: we truly don’t know what was there, so the only safe move is to leave whatever the write just wrote and log loudly.

Variants

Existed(Zeroizing<String>)

Absent

Unknown

Implementations

impl PriorKeychainState

fn capture(key: &str) -> Self

fn restore(&self, key: &str) -> Result<(), String>