feat(payload builder): transaction pool filter (#10542)

Co-authored-by: Matthias Seitz <matthias.seitz@outlook.de>

crates/transaction-pool/src/pool/best.rs

@@ -208,7 +208,7 @@ pub struct BestTransactionFilter<I, P> {
 
 impl<I, P> BestTransactionFilter<I, P> {
     /// Create a new [`BestTransactionFilter`] with the given predicate.
-    pub(crate) const fn new(best: I, predicate: P) -> Self {
+    pub const fn new(best: I, predicate: P) -> Self {
         Self { best, predicate }
     }
 }

crates/transaction-pool/src/traits.rs

@@ -814,6 +814,36 @@ impl<T> BestTransactions for std::iter::Empty<T> {
     fn set_skip_blobs(&mut self, _skip_blobs: bool) {}
 }
 
+/// A filter that allows to check if a transaction satisfies a set of conditions
+pub trait TransactionFilter {
+    /// The type of the transaction to check.
+    type Transaction;
+
+    /// Returns true if the transaction satisfies the conditions.
+    fn is_valid(&self, transaction: &Self::Transaction) -> bool;
+}
+
+/// A no-op implementation of [`TransactionFilter`] which
+/// marks all transactions as valid.
+#[derive(Debug, Clone)]
+pub struct NoopTransactionFilter<T>(std::marker::PhantomData<T>);
+
+// We can't derive Default because this forces T to be
+// Default as well, which isn't necessary.
+impl<T> Default for NoopTransactionFilter<T> {
+    fn default() -> Self {
+        Self(std::marker::PhantomData)
+    }
+}
+
+impl<T> TransactionFilter for NoopTransactionFilter<T> {
+    type Transaction = T;
+
+    fn is_valid(&self, _transaction: &Self::Transaction) -> bool {
+        true
+    }
+}
+
 /// A Helper type that bundles the best transactions attributes together.
 #[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub struct BestTransactionsAttributes {