reference a value from other linked table2

common/proto/tables_data.proto

@@ -258,6 +258,11 @@ message PutTableDataRequest {
   //   FAILED_PRECONDITION, instructing the caller to include X explicitly.
   //
   // Passing an empty map results in a no-op success response.
+  // A LINK may be supplied as {"id": "42", "version": "2"} to explicitly
+  // accept its target's current version, even when the row id is unchanged.
+  // Both values must be positive integers. The server rejects a stale version
+  // and atomically updates the saved FK version and all its stored linked values.
+  // A plain unchanged row id preserves the previously saved version and values.
   map<string, google.protobuf.Value> data = 4;
 
   // Required. Revision returned when this row was loaded or last saved.

common/src/proto/komp_ac.tables_data.rs

@@ -168,6 +168,11 @@ pub struct PutTableDataRequest {
     ///   FAILED_PRECONDITION, instructing the caller to include X explicitly.
     ///
     /// Passing an empty map results in a no-op success response.
+    /// A LINK may be supplied as {"id": "42", "version": "2"} to explicitly
+    /// accept its target's current version, even when the row id is unchanged.
+    /// Both values must be positive integers. The server rejects a stale version
+    /// and atomically updates the saved FK version and all its stored linked values.
+    /// A plain unchanged row id preserves the previously saved version and values.
     #[prost(map = "string, message", tag = "4")]
     pub data: ::std::collections::HashMap<
         ::prost::alloc::string::String,

komp-app/src/value.rs

@@ -59,10 +59,34 @@ pub fn convert_and_validate_data(
         .collect()
 }
 
+pub fn accepted_link_value(id: i64, version: i64) -> Result<Value, String> {
+    if id <= 0 || version <= 0 {
+        return Err("Selected link id and version must be positive".into());
+    }
+    Ok(Value {
+        kind: Some(Kind::StructValue(prost_types::Struct {
+            fields: [
+                ("id".into(), Value { kind: Some(Kind::StringValue(id.to_string())) }),
+                ("version".into(), Value { kind: Some(Kind::StringValue(version.to_string())) }),
+            ].into(),
+        })),
+    })
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn accepted_link_selection_keeps_full_precision() {
+        let selected = accepted_link_value(i64::MAX, 3).unwrap();
+        let Some(Kind::StructValue(fields)) = selected.kind else { panic!("Expected a link selection") };
+        assert_eq!(fields.fields["id"].kind, Some(Kind::StringValue(i64::MAX.to_string())));
+        assert_eq!(fields.fields["version"].kind, Some(Kind::StringValue("3".into())));
+        assert!(accepted_link_value(0, 3).is_err());
+        assert!(accepted_link_value(42, -1).is_err());
+    }
+
     #[test]
     fn preserves_large_integers_and_decimals_as_strings() {
         assert_eq!(