Add duplicate position open check for transactions

crates/core/app/src/action_handler/transaction.rs

@@ -15,8 +15,8 @@ mod stateless;
 
 use self::stateful::{claimed_anchor_is_valid, fee_greater_than_base_fee, fmd_parameters_valid};
 use stateless::{
-    check_memo_exists_if_outputs_absent_if_not, no_duplicate_spends, no_duplicate_votes,
-    num_clues_equal_to_num_outputs, valid_binding_signature,
+    check_memo_exists_if_outputs_absent_if_not, no_duplicate_position_opens, no_duplicate_spends,
+    no_duplicate_votes, num_clues_equal_to_num_outputs, valid_binding_signature,
 };
 
 #[async_trait]
@@ -32,6 +32,7 @@ impl ActionHandler for Transaction {
         valid_binding_signature(self)?;
         no_duplicate_spends(self)?;
         no_duplicate_votes(self)?;
+        no_duplicate_position_opens(self)?;
         num_clues_equal_to_num_outputs(self)?;
         check_memo_exists_if_outputs_absent_if_not(self)?;
 

crates/core/app/src/action_handler/transaction/stateless.rs

@@ -53,6 +53,19 @@ pub(super) fn no_duplicate_spends(tx: &Transaction) -> Result<()> {
     Ok(())
 }
 
+pub(super) fn no_duplicate_position_opens(tx: &Transaction) -> Result<()> {
+    // Disallow opening multiple positions with the same id.
+    let mut ids = BTreeSet::new();
+    for position_open in tx.position_openings() {
+        let id = position_open.position.id();
+        if let Some(duplicate) = ids.replace(id) {
+            anyhow::bail!("Duplicate position open in transaction: {}", duplicate);
+        }
+    }
+
+    Ok(())
+}
+
 pub fn num_clues_equal_to_num_outputs(tx: &Transaction) -> anyhow::Result<()> {
     if tx
         .transaction_body()