Check scanner.Err() after scan loop

source.go

@@ -3,6 +3,7 @@ package peco
 import (
 	"bufio"
 	"context"
+	"fmt"
 	"io"
 	"sync"
 	"time"
@@ -109,6 +110,12 @@ func (s *Source) Setup(ctx context.Context, state *Peco) {
 			}
 		}()
 
+		// scanErr captures any I/O error from the scanner goroutine.
+		// The goroutine writes to scanErr before closing the lines channel,
+		// and the outer loop reads it after lines is closed, so no mutex
+		// is needed.
+		var scanErr error
+
 		lines := make(chan string)
 		go func() {
 			var scanned int
@@ -129,6 +136,7 @@ func (s *Source) Setup(ctx context.Context, state *Peco) {
 				}
 				scanned++
 			}
+			scanErr = scanner.Err()
 		}()
 
 		state.Hub().SendStatusMsg(ctx, "Waiting for input...", 0)
@@ -156,6 +164,10 @@ func (s *Source) Setup(ctx context.Context, state *Peco) {
 			}
 		}
 
+		if scanErr != nil {
+			state.Hub().SendStatusMsg(ctx, fmt.Sprintf("Error reading input: %s", scanErr), 0)
+		}
+
 		if pdebug.Enabled {
 			pdebug.Printf("Read all %d lines from source", readCount)
 		}

source_test.go

@@ -1,12 +1,15 @@
 package peco
 
 import (
+	"errors"
 	"io"
 	"strings"
 	"sync"
 	"testing"
 	"time"
 
+	"context"
+
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -77,3 +80,66 @@ func TestSource(t *testing.T) {
 		}
 	}
 }
+
+// errorAfterReader returns data from the underlying reader, then once
+// the underlying reader is exhausted it returns a specified error.
+type errorAfterReader struct {
+	io.Reader
+	err    error
+	hitEOF bool
+}
+
+func (r *errorAfterReader) Read(p []byte) (int, error) {
+	if r.hitEOF {
+		return 0, r.err
+	}
+	n, err := r.Reader.Read(p)
+	if err == io.EOF {
+		r.hitEOF = true
+		if n > 0 {
+			return n, nil
+		}
+		return 0, r.err
+	}
+	return n, err
+}
+
+func TestSourceScannerErr(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	ig := newIDGen()
+	go ig.Run(ctx)
+
+	simulatedErr := errors.New("simulated I/O error")
+	r := &errorAfterReader{
+		Reader: strings.NewReader("line1\nline2\n"),
+		err:    simulatedErr,
+	}
+
+	s := NewSource("-", r, false, ig, 0, false, false)
+	p := New()
+	rh := &recordingHub{}
+	p.hub = rh
+	s.Setup(ctx, p)
+
+	// Verify lines read before the error are present
+	require.Equal(t, 2, s.Size(), "should have read 2 lines before the error")
+	l0, err := s.LineAt(0)
+	require.NoError(t, err)
+	require.Equal(t, "line1", l0.DisplayString())
+	l1, err := s.LineAt(1)
+	require.NoError(t, err)
+	require.Equal(t, "line2", l1.DisplayString())
+
+	// Verify the scanner error was reported via SendStatusMsg
+	msgs := rh.getStatusMsgs()
+	found := false
+	for _, msg := range msgs {
+		if strings.Contains(msg, "simulated I/O error") {
+			found = true
+			break
+		}
+	}
+	require.True(t, found, "expected scanner error in status messages, got: %v", msgs)
+}