Function resolve_context_vertex

atomic-core/src/apply/position.rs:250–267

Resolve a context position to a span. Given a position, finds the span that contains it or ends at it. For predecessors, we use `find_block_end` to find the span that ENDS at this position (since predecessors references the end of a predecessor). For successors, we use `find_block` to find the span starting at or containing this position. # Arguments `txn` - Transaction for graph lookups `pos`

(
    txn: &T,
    pos: Position<NodeId>,
    is_predecessor: bool,
)

/// - **Down context**: References the START of a successor span. We use
///   `find_block` to find a span containing this position.
pub fn resolve_context_vertex<T: GraphTxnT>(
    txn: &T,
    pos: Position<NodeId>,
    is_predecessor: bool,
) -> Result<GraphNode<NodeId>, LocalApplyError> {
    if pos.change.is_root() {
        return Ok(GraphNode::root());
    }

    let found = if is_predecessor {
        txn.find_block_end(pos)
    } else {
        txn.find_block(pos)
    }
    .map_err(|_| LocalApplyError::BlockNotFound { position: pos })?;

    Ok(adjust_for_mid_span(found, pos, is_predecessor))
}

// ---------------------------------------------------------------------------
// Mid-span adjustment