feat(OutputBuffer): expose scanner buffer size configuration

cmd.go

@@ -205,10 +205,17 @@ func NewCmdOptions(options Options, name string, args ...string) *Cmd {
 	if options.Buffered {
 		c.stdoutBuf = NewOutputBuffer()
 		c.stderrBuf = NewOutputBuffer()
+		if options.LineBufferSize > 0 {
+			c.stdoutBuf.SetScannerBufferSize(int(options.LineBufferSize))
+			c.stderrBuf.SetScannerBufferSize(int(options.LineBufferSize))
+		}
 	}
 
 	if options.CombinedOutput {
 		c.stdoutBuf = NewOutputBuffer()
+		if options.LineBufferSize > 0 {
+			c.stdoutBuf.SetScannerBufferSize(int(options.LineBufferSize))
+		}
 		c.stderrBuf = nil
 	}
 
@@ -239,11 +246,18 @@ func NewCmdOptions(options Options, name string, args ...string) *Cmd {
 // of the original object is lost. Cmd is one-use only, so if you need to restart
 // a Cmd, you need to Clone it.
 func (c *Cmd) Clone() *Cmd {
+	var lineBufferSize uint
+	if c.stdoutBuf != nil {
+		lineBufferSize = uint(c.stdoutBuf.scannerBufSize)
+	} else if c.stdoutStream != nil {
+		lineBufferSize = uint(c.stdoutStream.bufSize)
+	}
 	clone := NewCmdOptions(
 		Options{
 			Buffered:       c.stdoutBuf != nil,
 			CombinedOutput: c.stdoutBuf != nil,
 			Streaming:      c.stdoutStream != nil,
+			LineBufferSize: lineBufferSize,
 		},
 		c.Name,
 		c.Args...,
@@ -375,11 +389,16 @@ func (c *Cmd) Status() Status {
 		if !c.final {
 			if c.stdoutBuf != nil {
 				c.status.Stdout = c.stdoutBuf.Lines()
+				if err := c.stdoutBuf.Err(); err != nil && c.status.Error == nil {
+					c.status.Error = err
+				}
 				c.stdoutBuf = nil // release buffers
-
 			}
 			if c.stderrBuf != nil {
 				c.status.Stderr = c.stderrBuf.Lines()
+				if err := c.stderrBuf.Err(); err != nil && c.status.Error == nil {
+					c.status.Error = err
+				}
 				c.stderrBuf = nil // release buffers
 			}
 			c.final = true
@@ -582,20 +601,41 @@ func (c *Cmd) run(in io.Reader) {
 // While runnableCmd is running, call stdout.Lines() to read all output
 // currently written.
 type OutputBuffer struct {
-	buf   *bytes.Buffer
-	lines []string
+	buf            *bytes.Buffer
+	lines          []string
+	scannerBufSize int
+	scanErr        error
 	*sync.Mutex
 }
 
 // NewOutputBuffer creates a new output buffer. The buffer is unbounded and safe
 // for multiple goroutines to read while the command is running by calling Lines.
 func NewOutputBuffer() *OutputBuffer {
-	out := &OutputBuffer{
-		buf:   &bytes.Buffer{},
-		lines: []string{},
-		Mutex: &sync.Mutex{},
+	return &OutputBuffer{
+		buf:            &bytes.Buffer{},
+		lines:          []string{},
+		scannerBufSize: bufio.MaxScanTokenSize,
+		Mutex:          &sync.Mutex{},
 	}
-	return out
+}
+
+// SetScannerBufferSize sets the maximum token size for the bufio.Scanner used
+// by Lines(). The default is bufio.MaxScanTokenSize (64KB). Increase this value
+// if Lines() truncates output because a line exceeds that limit (Err() will
+// return a non-nil error in that case). Must be called before the command starts.
+func (rw *OutputBuffer) SetScannerBufferSize(n int) {
+	rw.Lock()
+	rw.scannerBufSize = n
+	rw.Unlock()
+}
+
+// Err returns the last error set by Lines(), if any. A non-nil error indicates
+// that output was truncated because a line exceeded the scanner buffer size.
+// Use SetScannerBufferSize to increase the limit.
+func (rw *OutputBuffer) Err() error {
+	rw.Lock()
+	defer rw.Unlock()
+	return rw.scanErr
 }
 
 // Write makes OutputBuffer implement the io.Writer interface. Do not call
@@ -610,14 +650,22 @@ func (rw *OutputBuffer) Write(p []byte) (n int, err error) {
 // Lines returns lines of output written by the Cmd. It is safe to call while
 // the Cmd is running and after it has finished. Subsequent calls returns more
 // lines, if more lines were written. "\r\n" are stripped from the lines.
+//
+// If a line exceeds the scanner buffer size (set via SetScannerBufferSize,
+// default bufio.MaxScanTokenSize / 64KB), scanning stops and Err() returns
+// the error. Use SetScannerBufferSize to increase the limit.
 func (rw *OutputBuffer) Lines() []string {
 	rw.Lock()
 	// Scanners are io.Readers which effectively destroy the buffer by reading
 	// to EOF. So once we scan the buf to lines, the buf is empty again.
 	s := bufio.NewScanner(rw.buf)
+	s.Buffer(make([]byte, rw.scannerBufSize), rw.scannerBufSize)
 	for s.Scan() {
 		rw.lines = append(rw.lines, s.Text())
 	}
+	if err := s.Err(); err != nil {
+		rw.scanErr = err
+	}
 	rw.Unlock()
 	return rw.lines
 }

cmd_test.go

@@ -12,7 +12,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/go-cmd/cmd"
+	"github.com/orus-io/cmd"
 	"github.com/go-test/deep"
 )
 
@@ -1479,3 +1479,124 @@ func TestCmdLineBufferIncrease(t *testing.T) {
 	}
 	<-catStderrStatus
 }
+
+func TestOutputBufferDefaultScannerBufSize(t *testing.T) {
+	// Default scanner buffer size is bufio.MaxScanTokenSize (64KB).
+	// A line within that limit must be returned correctly.
+	buf := cmd.NewOutputBuffer()
+	line := bytes.Repeat([]byte("x"), 1000)
+	line = append(line, '\n')
+	buf.Write(line)
+	lines := buf.Lines()
+	if len(lines) != 1 {
+		t.Fatalf("expected 1 line, got %d", len(lines))
+	}
+	if len(lines[0]) != 1000 {
+		t.Errorf("expected line of 1000 bytes, got %d", len(lines[0]))
+	}
+	if err := buf.Err(); err != nil {
+		t.Errorf("expected no error, got: %v", err)
+	}
+}
+
+func TestOutputBufferLongLineTruncation(t *testing.T) {
+	// A line exceeding bufio.MaxScanTokenSize (64KB) with the default buffer
+	// must set Err() to a non-nil error, and Lines() must stop at that point.
+	buf := cmd.NewOutputBuffer()
+
+	longLine := bytes.Repeat([]byte("x"), 65*1024) // 65KB > 64KB default
+	longLine = append(longLine, '\n')
+	after := []byte("after\n")
+	buf.Write(longLine)
+	buf.Write(after)
+
+	lines := buf.Lines()
+	if buf.Err() == nil {
+		t.Error("expected a non-nil error from Err() after long line, got nil")
+	}
+	for _, l := range lines {
+		if l == "after" {
+			t.Error("lines after the oversized line should not appear when truncated")
+		}
+	}
+}
+
+func TestOutputBufferSetScannerBufferSize(t *testing.T) {
+	// SetScannerBufferSize allows reading lines larger than 64KB.
+	buf := cmd.NewOutputBuffer()
+	buf.SetScannerBufferSize(256 * 1024) // 256KB
+
+	longLine := bytes.Repeat([]byte("y"), 65*1024) // 65KB
+	longLine = append(longLine, '\n')
+	buf.Write(longLine)
+	buf.Write([]byte("after\n"))
+
+	lines := buf.Lines()
+	if err := buf.Err(); err != nil {
+		t.Errorf("expected no error with enlarged buffer, got: %v", err)
+	}
+	if len(lines) != 2 {
+		t.Fatalf("expected 2 lines, got %d", len(lines))
+	}
+	if len(lines[0]) != 65*1024 {
+		t.Errorf("expected first line of %d bytes, got %d", 65*1024, len(lines[0]))
+	}
+	if lines[1] != "after" {
+		t.Errorf("expected second line 'after', got %q", lines[1])
+	}
+}
+
+func TestOutputBufferLineBufferSizeOption(t *testing.T) {
+	// Options.LineBufferSize propagates to OutputBuffer when Buffered is true.
+	const bufSize = 256 * 1024 // 256KB
+	p := cmd.NewCmdOptions(
+		cmd.Options{Buffered: true, LineBufferSize: bufSize},
+		"echo",
+		string(bytes.Repeat([]byte("z"), 65*1024)), // 65KB argument → one long output line
+	)
+	status := <-p.Start()
+	if status.Error != nil {
+		t.Fatalf("command error: %v", status.Error)
+	}
+	if len(status.Stdout) != 1 {
+		t.Fatalf("expected 1 line of stdout, got %d", len(status.Stdout))
+	}
+	if len(status.Stdout[0]) != 65*1024 {
+		t.Errorf("expected stdout line of %d bytes, got %d", 65*1024, len(status.Stdout[0]))
+	}
+}
+
+func TestCmdStatusErrorOnScannerOverflow(t *testing.T) {
+	// When a line exceeds the scanner buffer size, status.Error must be non-nil
+	// so the caller can detect the truncation without inspecting OutputBuffer directly.
+	p := cmd.NewCmdOptions(
+		cmd.Options{Buffered: true}, // default 64KB limit
+		"echo",
+		string(bytes.Repeat([]byte("x"), 65*1024)), // 65KB > 64KB
+	)
+	status := <-p.Start()
+	if status.Error == nil {
+		t.Error("expected status.Error to be non-nil on scanner overflow, got nil")
+	}
+}
+
+func TestOutputBufferClonePropagatesScannerBufSize(t *testing.T) {
+	// Clone must propagate LineBufferSize to the cloned Cmd's OutputBuffer.
+	const bufSize = 256 * 1024
+	p := cmd.NewCmdOptions(
+		cmd.Options{Buffered: true, LineBufferSize: bufSize},
+		"echo",
+		string(bytes.Repeat([]byte("z"), 65*1024)),
+	)
+	clone := p.Clone()
+	status := <-clone.Start()
+	if status.Error != nil {
+		t.Fatalf("clone command error: %v", status.Error)
+	}
+	if len(status.Stdout) != 1 {
+		t.Fatalf("expected 1 line from clone stdout, got %d", len(status.Stdout))
+	}
+	if len(status.Stdout[0]) != 65*1024 {
+		t.Errorf("expected clone stdout line of %d bytes, got %d", 65*1024, len(status.Stdout[0]))
+	}
+}

cmd_windows_test.go

@@ -11,7 +11,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/go-cmd/cmd"
+	"github.com/orus-io/cmd"
 	"github.com/go-test/deep"
 )
 

examples/blocking-buffered/main.go

@@ -3,7 +3,7 @@ package main
 import (
 	"fmt"
 
-	"github.com/go-cmd/cmd"
+	"github.com/orus-io/cmd"
 )
 
 func main() {

examples/blocking-streaming/main.go

@@ -6,7 +6,7 @@ import (
 	"fmt"
 	"os"
 
-	"github.com/go-cmd/cmd"
+	"github.com/orus-io/cmd"
 )
 
 func main() {

go.mod

@@ -1,4 +1,4 @@
-module github.com/go-cmd/cmd
+module github.com/orus-io/cmd
 
 go 1.20