mining: add tx lookup IPC methods and integration coverage

Add Mining interface methods getTransactionsByTxID and
getTransactionsByWitnessID to the capnp schema.

Expand integration tests to call both methods with empty inputs, a real
mempool transaction id and witness id, and unknown ids, verifying serialized
transaction bytes for hits and empty results for misses.

Author: Sjors

capnp/mining.capnp

@@ -23,6 +23,8 @@ interface Mining $Proxy.wrap("interfaces::Mining") {
     createNewBlock @4 (context :Proxy.Context, options: BlockCreateOptions, cooldown: Bool = true) -> (result: BlockTemplate);
     checkBlock @5 (context :Proxy.Context, block: Data, options: BlockCheckOptions) -> (reason: Text, debug: Text, result: Bool);
     interrupt @6 () -> ();
+    getTransactionsByTxID @7 (context :Proxy.Context, txids: List(Data)) -> (result: List(Data));
+    getTransactionsByWitnessID @8 (context :Proxy.Context, wtxids: List(Data)) -> (result: List(Data));
 }
 
 interface BlockTemplate $Proxy.wrap("interfaces::BlockTemplate") {

tests/test.rs

@@ -270,6 +270,102 @@ async fn mining_block_template_lifecycle() {
         .await;
 }
 
+/// getTransactionsByTxID and getTransactionsByWitnessID with empty lists and
+/// with a non-existent txid/wtxid.
+#[tokio::test]
+// Serialized because this test may mine blocks to recover wallet funding.
+#[serial_test::serial]
+async fn mining_get_transactions() {
+    let path = unix_socket_path();
+    let rpc_network = connect_unix_stream(path).await;
+    let rpc_system = RpcSystem::new(Box::new(rpc_network), None);
+    LocalSet::new()
+        .run_until(async move {
+            let (client, thread) = bootstrap(rpc_system).await;
+            let mining = make_mining(&client, &thread).await;
+            let wallet = bitcoin_test_wallet();
+            ensure_wallet_loaded_and_funded(&wallet);
+            let (real_txid, real_wtxid, real_raw_tx) = create_mempool_self_transfer(&wallet);
+
+            // getTransactionsByTxID — empty list should return empty list.
+            let mut req = mining.get_transactions_by_tx_i_d_request();
+            req.get().get_context().unwrap().set_thread(thread.clone());
+            req.get().init_txids(0);
+            let resp = req.send().promise.await.unwrap();
+            let results = resp.get().unwrap().get_result().unwrap();
+            assert_eq!(
+                results.len(),
+                0,
+                "empty txid list should return empty results"
+            );
+
+            // getTransactionsByTxID — return real mempool tx and empty for unknown id.
+            let fake_txid = [0x42u8; 32];
+            let mut req = mining.get_transactions_by_tx_i_d_request();
+            req.get().get_context().unwrap().set_thread(thread.clone());
+            {
+                let mut txids = req.get().init_txids(2);
+                txids.set(0, &real_txid);
+                txids.set(1, &fake_txid);
+            }
+            let resp = req.send().promise.await.unwrap();
+            let results = resp.get().unwrap().get_result().unwrap();
+            assert_eq!(
+                results.len(),
+                2,
+                "should return one entry per requested txid, including misses"
+            );
+            assert_eq!(
+                results.get(0).unwrap(),
+                real_raw_tx.as_slice(),
+                "known txid should return serialized transaction"
+            );
+            assert!(
+                results.get(1).unwrap().is_empty(),
+                "non-existent txid should return empty data"
+            );
+
+            // getTransactionsByWitnessID — empty list should return empty list.
+            let mut req = mining.get_transactions_by_witness_i_d_request();
+            req.get().get_context().unwrap().set_thread(thread.clone());
+            req.get().init_wtxids(0);
+            let resp = req.send().promise.await.unwrap();
+            let results = resp.get().unwrap().get_result().unwrap();
+            assert_eq!(
+                results.len(),
+                0,
+                "empty wtxid list should return empty results"
+            );
+
+            // getTransactionsByWitnessID — return real mempool tx and empty for unknown id.
+            let fake_wtxid = [0x43u8; 32];
+            let mut req = mining.get_transactions_by_witness_i_d_request();
+            req.get().get_context().unwrap().set_thread(thread.clone());
+            {
+                let mut wtxids = req.get().init_wtxids(2);
+                wtxids.set(0, &real_wtxid);
+                wtxids.set(1, &fake_wtxid);
+            }
+            let resp = req.send().promise.await.unwrap();
+            let results = resp.get().unwrap().get_result().unwrap();
+            assert_eq!(
+                results.len(),
+                2,
+                "should return one entry per requested wtxid, including misses"
+            );
+            assert_eq!(
+                results.get(0).unwrap(),
+                real_raw_tx.as_slice(),
+                "known wtxid should return serialized transaction"
+            );
+            assert!(
+                results.get(1).unwrap().is_empty(),
+                "non-existent wtxid should return empty data"
+            );
+        })
+        .await;
+}
+
 /// checkBlock with a template block payload, and interrupt.
 #[tokio::test]
 // Serialized because interrupt() can affect other in-flight mining waits.