Function validate_can_apply

atomic-core/src/apply/change.rs:206–232

Check if applying a change would succeed (without actually applying). This performs validation checks: - Change not already on view - All dependencies present # Arguments `txn` - The transaction to check against `view` - The view to check `change_id` - The internal ID of the change `change_hash` - The hash of the change `change` - The change to validate # Returns `Ok(())` if the change can be

(
    txn: &T,
    view: &ViewState,
    change_id: NodeId,
    change_hash: &Hash,
    change: &Change,
)

///
/// `Ok(())` if the change can be applied, or an error describing why not.
pub fn validate_can_apply<T: ViewTxnT + GraphTxnT>(
    txn: &T,
    view: &ViewState,
    change_id: NodeId,
    change_hash: &Hash,
    change: &Change,
) -> Result<(), LocalApplyError> {
    // Check if already applied
    if is_change_on_view(txn, view, change_id).map_err(|e| LocalApplyError::Internal {
        message: format!("Failed to check view: {}", e),
    })? {
        return Err(LocalApplyError::ChangeAlreadyApplied { hash: *change_hash });
    }

    // Check dependencies
    let missing = verify_dependencies(txn, change).map_err(|e| LocalApplyError::Internal {
        message: format!("Failed to verify dependencies: {}", e),
    })?;

    if let Some(first_missing) = missing.first() {
        return Err(LocalApplyError::DependencyMissing {
            hash: *first_missing,
        });
    }

    Ok(())
}

#[cfg(test)]
mod tests {