Report EOF after the prompt input stream ends

interact/prompt.go

@@ -43,11 +43,14 @@ func promptLines(in io.Reader) chan result {
 	promptReaders.ch = ch
 
 	go func(r io.Reader) {
+		defer close(ch)
 		s := bufio.NewScanner(r)
 		for s.Scan() {
 			ch <- result{answer: strings.TrimSpace(s.Text())}
 		}
-		ch <- result{err: s.Err()}
+		if err := s.Err(); err != nil {
+			ch <- result{err: err}
+		}
 	}(in)
 
 	return ch
@@ -64,7 +67,10 @@ func Prompt(ctx context.Context, query, defaultAnswer string) (string, error) {
 	_, _ = fmt.Fprintf(cutypes.Output, "%s [%s]: ", query, defaultAnswer)
 
 	select {
-	case r := <-promptLines(cutypes.Input):
+	case r, ok := <-promptLines(cutypes.Input):
+		if !ok {
+			return "", io.EOF
+		}
 		if r.err != nil {
 			return "", r.err
 		}

interact/prompt_eof_test.go

@@ -0,0 +1,45 @@
+package interact_test
+
+import (
+	"context"
+	"errors"
+	"io"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/gookit/cliui"
+	"github.com/gookit/cliui/interact"
+	"github.com/gookit/goutil/x/assert"
+)
+
+func TestPromptReportsStreamEOF(t *testing.T) {
+	for _, tc := range []struct {
+		name, input string
+		answers     []string
+	}{
+		{name: "empty stream"},
+		{name: "one line", input: "Ada\n", answers: []string{"Ada"}},
+		{name: "final unterminated line", input: "Ada", answers: []string{"Ada"}},
+		{name: "blank line uses default", input: "\n", answers: []string{"fallback"}},
+		{name: "several lines", input: "Ada\nGrace\n", answers: []string{"Ada", "Grace"}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			cliui.CustomIO(strings.NewReader(tc.input), io.Discard)
+			defer cliui.ResetIO()
+			ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+			defer cancel()
+			for _, want := range tc.answers {
+				got, err := interact.Prompt(ctx, "Name", "fallback")
+				assert.NoErr(t, err)
+				assert.Eq(t, want, got)
+			}
+			for i := 0; i < 3; i++ {
+				got, err := interact.Prompt(ctx, "Name", "fallback")
+				if !errors.Is(err, io.EOF) || got != "" {
+					t.Fatalf("Prompt after EOF #%d = %q,%v; want empty answer and EOF", i+1, got, err)
+				}
+			}
+		})
+	}
+}