op-node/rollup/derive: also mark IsLast as true when `closed && m…

…axDataSize==readyBytes` (ethereum-optimism#9696)

* also mark IsLast as true when maxDataSize==readyBytes

* add TestOutputFrameNoEmptyLastFrame

* fix typo

* fix for review

op-e2e/actions/garbage_channel_out.go

@@ -207,10 +207,10 @@ func (co *GarbageChannelOut) OutputFrame(w *bytes.Buffer, maxSize uint64) (uint1
 	// Fixed overhead: 32 + 8 + 2 + 4 + 1  = 47 bytes.
 	// Add one extra byte for the version byte (for the entire L1 tx though)
 	maxDataSize := maxSize - 47 - 1
-	if maxDataSize > uint64(co.buf.Len()) {
+	if maxDataSize >= uint64(co.buf.Len()) {
 		maxDataSize = uint64(co.buf.Len())
 		// If we are closed & will not spill past the current frame
-		// mark it is the final frame of the channel.
+		// mark it as the final frame of the channel.
 		if co.closed {
 			f.IsLast = true
 		}

op-node/rollup/derive/channel_out.go

@@ -322,10 +322,10 @@ func createEmptyFrame(id ChannelID, frame uint64, readyBytes int, closed bool, m
 
 	// Copy data from the local buffer into the frame data buffer
 	maxDataSize := maxSize - FrameV0OverHeadSize
-	if maxDataSize > uint64(readyBytes) {
+	if maxDataSize >= uint64(readyBytes) {
 		maxDataSize = uint64(readyBytes)
 		// If we are closed & will not spill past the current frame
-		// mark it is the final frame of the channel.
+		// mark it as the final frame of the channel.
 		if closed {
 			f.IsLast = true
 		}

op-node/rollup/derive/channel_out_test.go

@@ -2,7 +2,9 @@ package derive
 
 import (
 	"bytes"
+	"io"
 	"math/big"
+	"math/rand"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -68,6 +70,27 @@ func TestOutputFrameSmallMaxSize(t *testing.T) {
 	}
 }
 
+func TestOutputFrameNoEmptyLastFrame(t *testing.T) {
+	cout, err := NewChannelOut(SingularBatchType, &nonCompressor{}, nil)
+	require.NoError(t, err)
+
+	rng := rand.New(rand.NewSource(0x543331))
+	chainID := big.NewInt(rng.Int63n(1000))
+	txCount := 1
+	singularBatch := RandomSingularBatch(rng, txCount, chainID)
+
+	written, err := cout.AddSingularBatch(singularBatch, 0)
+	require.NoError(t, err)
+
+	require.NoError(t, cout.Close())
+
+	var buf bytes.Buffer
+	// Output a frame which needs exactly `written` bytes. This frame is expected to be the last frame.
+	_, err = cout.OutputFrame(&buf, written+FrameV0OverHeadSize)
+	require.ErrorIs(t, err, io.EOF)
+
+}
+
 // TestRLPByteLimit ensures that stream encoder is properly limiting the length.
 // It will decode the input if `len(input) <= inputLimit`.
 func TestRLPByteLimit(t *testing.T) {