fix(components/execd): fix single-line output truncation issue

components/execd/pkg/runtime/command_common.go

@@ -16,9 +16,11 @@ package runtime
 
 import (
 	"bufio"
+	"bytes"
 	"io"
 	"os"
 	"path/filepath"
+	"sync"
 	"time"
 )
 
@@ -28,13 +30,14 @@ func (c *Controller) tailStdPipe(file string, onExecute func(text string), done
 	ticker := time.NewTicker(100 * time.Millisecond)
 	defer ticker.Stop()
 
+	mutex := &sync.Mutex{}
 	for {
 		select {
 		case <-done:
-			c.readFromPos(file, lastPos, onExecute)
+			c.readFromPos(mutex, file, lastPos, onExecute)
 			return
 		case <-ticker.C:
-			newPos := c.readFromPos(file, lastPos, onExecute)
+			newPos := c.readFromPos(mutex, file, lastPos, onExecute)
 			lastPos = newPos
 		}
 	}
@@ -81,7 +84,12 @@ func (c *Controller) stderrFileName(session string) string {
 }
 
 // readFromPos streams new content from a file starting at startPos.
-func (c *Controller) readFromPos(filepath string, startPos int64, onExecute func(string)) int64 {
+func (c *Controller) readFromPos(mutex *sync.Mutex, filepath string, startPos int64, onExecute func(string)) int64 {
+	if !mutex.TryLock() {
+		return -1
+	}
+	defer mutex.Unlock()
+
 	file, err := os.Open(filepath)
 	if err != nil {
 		return startPos
@@ -90,32 +98,39 @@ func (c *Controller) readFromPos(filepath string, startPos int64, onExecute func
 
 	_, _ = file.Seek(startPos, 0) //nolint:errcheck
 
-	scanner := bufio.NewScanner(file)
-	// Support long lines and treat both \n and \r as delimiters to keep progress output.
-	scanner.Buffer(make([]byte, 0, 64*1024), 5*1024*1024) // 5MB max token
-	scanner.Split(func(data []byte, atEOF bool) (advance int, token []byte, err error) {
-		for i, b := range data {
-			if b == '\n' || b == '\r' {
-				// Treat \r\n as a single delimiter to avoid empty tokens.
-				if b == '\r' && i+1 < len(data) && data[i+1] == '\n' {
-					return i + 2, data[:i], nil
-				}
-				return i + 1, data[:i], nil
+	reader := bufio.NewReader(file)
+	var buffer bytes.Buffer
+	var currentPos int64 = startPos
+
+	for {
+		b, err := reader.ReadByte()
+		if err != nil {
+			if err == io.EOF {
+				// If buffer has content but no newline, it's an incomplete line, don't output
+				break
 			}
+			break
 		}
-		if atEOF && len(data) > 0 {
-			return len(data), data, nil
+		currentPos++
+
+		// Check if it's a line terminator (\n or \r)
+		if b == '\n' || b == '\r' {
+			// If buffer has content, output this line
+			if buffer.Len() > 0 {
+				onExecute(buffer.String())
+				buffer.Reset()
+			}
+			// Skip line terminator
+			continue
 		}
-		return 0, nil, nil
-	})
 
-	for scanner.Scan() {
-		onExecute(scanner.Text())
-	}
-	if err := scanner.Err(); err != nil {
-		return startPos
+		buffer.WriteByte(b)
 	}
 
 	endPos, _ := file.Seek(0, 1)
+	// If the last read position doesn't end with a newline, return the buffer start position
+	if buffer.Len() > 0 {
+		return currentPos - int64(buffer.Len())
+	}
 	return endPos
 }

components/execd/pkg/runtime/command_test.go

@@ -20,6 +20,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -32,14 +33,16 @@ func TestReadFromPos_SplitsOnCRAndLF(t *testing.T) {
 	tmp := t.TempDir()
 	logFile := filepath.Join(tmp, "stdout.log")
 
+	mutex := &sync.Mutex{}
+
 	initial := "line1\nprog 10%\rprog 20%\rprog 30%\nlast\n"
 	if err := os.WriteFile(logFile, []byte(initial), 0o644); err != nil {
 		t.Fatalf("write initial file: %v", err)
 	}
 
 	var got []string
 	c := &Controller{}
-	nextPos := c.readFromPos(logFile, 0, func(s string) { got = append(got, s) })
+	nextPos := c.readFromPos(mutex, logFile, 0, func(s string) { got = append(got, s) })
 
 	want := []string{"line1", "prog 10%", "prog 20%", "prog 30%", "last"}
 	if len(got) != len(want) {
@@ -64,7 +67,7 @@ func TestReadFromPos_SplitsOnCRAndLF(t *testing.T) {
 	_ = f.Close()
 
 	got = got[:0]
-	c.readFromPos(logFile, nextPos, func(s string) { got = append(got, s) })
+	c.readFromPos(mutex, logFile, nextPos, func(s string) { got = append(got, s) })
 	want = []string{"tail1", "tail2"}
 	if len(got) != len(want) {
 		t.Fatalf("incremental token count: got %d want %d", len(got), len(want))
@@ -88,7 +91,7 @@ func TestReadFromPos_LongLine(t *testing.T) {
 
 	var got []string
 	c := &Controller{}
-	c.readFromPos(logFile, 0, func(s string) { got = append(got, s) })
+	c.readFromPos(&sync.Mutex{}, logFile, 0, func(s string) { got = append(got, s) })
 
 	if len(got) != 1 {
 		t.Fatalf("expected one token, got %d", len(got))