feat: purpose -1 to return all unconfirmed transactions in UnconfirmedTxs RPC (#1675)

## Description

Instead of creating a new RPC method that returns all the unconfirmed
mempool transactions, I used -1 as a special flag to do that. I think
it's fine to do so. If it's not, can always define a new endpoint.

#### PR checklist

- [ ] Tests written/updated
- [ ] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [ ] Updated relevant documentation (`docs/` or `spec/`) and code
comments

Author: rach-id

rpc/client/rpc_test.go

@@ -404,6 +404,38 @@ func TestUnconfirmedTxs(t *testing.T) {
 	mempool.Flush()
 }
 
+func TestUncappedUnconfirmedTxs(t *testing.T) {
+	mempool := node.Mempool()
+	numberOfTransactions := 120 // needs to be greater than maxPerPage const
+	for i := 0; i < numberOfTransactions; i++ {
+		_, _, tx := MakeTxKV()
+
+		ch := make(chan *abci.Response, 1)
+		err := mempool.CheckTx(tx, func(resp *abci.Response) { ch <- resp }, mempl.TxInfo{})
+		require.NoError(t, err)
+
+		// wait for tx to arrive in mempoool.
+		select {
+		case <-ch:
+		case <-time.After(5 * time.Second):
+			t.Error("Timed out waiting for CheckTx callback")
+		}
+	}
+
+	for _, c := range GetClients() {
+		mc := c.(client.MempoolClient)
+		limit := -1 // set the limit to -1 to return everything
+		res, err := mc.UnconfirmedTxs(context.Background(), &limit)
+		require.NoError(t, err)
+
+		assert.Equal(t, numberOfTransactions, res.Count)
+		assert.Equal(t, numberOfTransactions, res.Total)
+		assert.Equal(t, mempool.SizeBytes(), res.TotalBytes)
+	}
+
+	mempool.Flush()
+}
+
 func TestNumUnconfirmedTxs(t *testing.T) {
 	_, _, tx := MakeTxKV()
 

rpc/core/mempool.go

@@ -154,9 +154,13 @@ func BroadcastTxCommit(ctx *rpctypes.Context, tx types.Tx) (*ctypes.ResultBroadc
 // UnconfirmedTxs gets unconfirmed transactions (maximum ?limit entries)
 // including their number.
 // More: https://docs.cometbft.com/v0.34/rpc/#/Info/unconfirmed_txs
+// If limitPtr == -1, it will return all the unconfirmed transactions in the mempool.
 func UnconfirmedTxs(ctx *rpctypes.Context, limitPtr *int) (*ctypes.ResultUnconfirmedTxs, error) {
-	// reuse per_page validator
-	limit := validatePerPage(limitPtr)
+	limit := *limitPtr
+	if limit != -1 {
+		// reuse per_page validator
+		limit = validatePerPage(limitPtr)
+	}
 	env := GetEnvironment()
 
 	txs := env.Mempool.ReapMaxTxs(limit)

rpc/openapi/openapi.yaml

@@ -824,7 +824,7 @@ paths:
       parameters:
         - in: query
           name: limit
-          description: Maximum number of unconfirmed transactions to return (max 100)
+          description: Maximum number of unconfirmed transactions to return (max 100). If set to -1, it will return all the unconfirmed mempool transactions.
           required: false
           schema:
             type: integer