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fix: Return error if too few snapshots for latest~N #459

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Merged
aawsome merged 1 commit into from
Jan 9, 2026
Merged

fix: Return error if too few snapshots for latest~N #459

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55 changes: 33 additions & 22 deletions crates/core/src/repofile/snapshotfile.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -714,7 +714,7 @@ impl SnapshotFile {
&requests.starts_with,
);
});
let latest = Self::latest_n_from_iter(max_n, iter);
let latest = Self::latest_n_from_iter(max_n, iter)?;
let vec_ids_starts_with = ids_starts_with.assert_found(&requests.starts_with)?;
Ok(requests.map_results(&latest, vec_ids_starts_with, vec_ids))
}
Expand All @@ -740,11 +740,29 @@ impl SnapshotFile {
Self::latest_n(be, predicate, p, 0)
}

fn latest_n_from_iter(n: usize, iter: impl IntoIterator<Item = Self>) -> Vec<Self> {
iter.into_iter()
fn latest_n_from_iter(
n: usize,
iter: impl IntoIterator<Item = Self>,
) -> RusticResult<Vec<Self>> {
let latest: Vec<_> = iter
.into_iter()
// find n+1 smallest elements when sorting in decreasing time order
.k_smallest_by(n + 1, |s1, s2| s2.time.cmp(&s1.time))
.collect()
.collect();

if latest.len() > n {
Ok(latest)
} else if n == 0 {
Err(RusticError::new(
ErrorKind::Repository,
"No snapshots found. Please make sure there are snapshots in the repository.",
))
} else {
Err(RusticError::new(
ErrorKind::Repository,
"No snapshots found for latest~{n}. Please make sure there are more than {n} snapshots in the repository.",
).attach_context("n", n.to_string()))
}
}

/// Get the latest [`SnapshotFile`] from the backend
Expand All @@ -771,26 +789,10 @@ impl SnapshotFile {
p.set_title("getting latest~N snapshot...");
}
let mut snapshots =
Self::latest_n_from_iter(n, Self::iter_all_from_backend(be, predicate, p)?);

let len = snapshots.len();
let latest = (len > n).then_some(snapshots.pop()).flatten(); // we want the latest element if we found n+1 snapshots
Self::latest_n_from_iter(n, Self::iter_all_from_backend(be, predicate, p)?)?;

p.finish();

latest.ok_or_else(|| {
if n == 0 {
RusticError::new(
ErrorKind::Repository,
"No snapshots found. Please make sure there are snapshots in the repository.",
)
} else {
RusticError::new(
ErrorKind::Repository,
"No snapshots found for latest~{n}. Please make sure there are more than {n} snapshots in the repository.",
).attach_context("n", n.to_string())
}
})
Ok(snapshots.pop().unwrap()) // we want the latest element if we found n+1 snapshots
}

/// Get a [`SnapshotFile`] from the backend by (part of the) id
Expand Down Expand Up @@ -1845,6 +1847,15 @@ mod tests {
let ids: Vec<_> = snaps.iter().map(|sn| *sn.id).collect();
assert_eq!(ids, vec![id3, id2]);

// not enough latest snapshots
let latest_n3 = SnapshotFile::from_strs(&be, &["003", "latest~3"], |_sn| true, &NoProgress);
let latest_n3_err = latest_n3.unwrap_err().to_string();
let expected = "No snapshots found for latest~3.";
assert!(
latest_n3_err.contains(expected),
"Err is: {latest_n3_err}\n\nShould contain: {expected}",
);

// only (parts of) ids
let snaps = SnapshotFile::from_strs(
&be,
Expand Down
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