From c41336bc776c5a654287944672e93893bc07fc28 Mon Sep 17 00:00:00 2001
From: Bishwa Shrestha <bishwa.shrestha@gmail.com>
Date: Wed, 21 Oct 2020 20:10:06 +0200
Subject: [PATCH] Exit with error if UI input scan fails (#26509)

---
 command/ui_input.go      | 10 ++++++++--
 command/ui_input_test.go | 20 ++++++++++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/command/ui_input.go b/command/ui_input.go
index 962fa76de..9f3410778 100644
--- a/command/ui_input.go
+++ b/command/ui_input.go
@@ -39,6 +39,7 @@ type UIInput struct {
 
 	listening int32
 	result    chan string
+	err       chan string
 
 	interrupted bool
 	l           sync.Mutex
@@ -140,12 +141,16 @@ func (i *UIInput) Input(ctx context.Context, opts *terraform.InputOpts) (string,
 		}
 		if err != nil {
 			log.Printf("[ERR] UIInput scan err: %s", err)
+			i.err <- string(err.Error())
+		} else {
+			i.result <- strings.TrimRightFunc(line, unicode.IsSpace)
 		}
-
-		i.result <- strings.TrimRightFunc(line, unicode.IsSpace)
 	}()
 
 	select {
+	case err := <-i.err:
+		return "", errors.New(err)
+
 	case line := <-i.result:
 		fmt.Fprint(w, "\n")
 
@@ -174,6 +179,7 @@ func (i *UIInput) Input(ctx context.Context, opts *terraform.InputOpts) (string,
 
 func (i *UIInput) init() {
 	i.result = make(chan string)
+	i.err = make(chan string)
 
 	if i.Colorize == nil {
 		i.Colorize = &colorstring.Colorize{
diff --git a/command/ui_input_test.go b/command/ui_input_test.go
index 23539a132..7bda3962d 100644
--- a/command/ui_input_test.go
+++ b/command/ui_input_test.go
@@ -97,3 +97,23 @@ func TestUIInputInput_spaces(t *testing.T) {
 		t.Fatalf("unexpected input: %s", v)
 	}
 }
+
+func TestUIInputInput_Error(t *testing.T) {
+	i := &UIInput{
+		Reader: bytes.NewBuffer(nil),
+		Writer: bytes.NewBuffer(nil),
+	}
+
+	v, err := i.Input(context.Background(), &terraform.InputOpts{})
+	if err == nil {
+		t.Fatalf("Error is not 'nil'")
+	}
+
+	if err.Error() != "EOF" {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if v != "" {
+		t.Fatalf("input must be empty")
+	}
+}