英文:
Problem with testing cli prompts interactively, scanner is not waiting for user input
问题
我尝试编写一个测试来验证命令行提示，模拟用户对某些程序输出的响应中的输入。
如何使scanner.Scan等待其他写入？
我目前的代码如下：
b := &bytes.Buffer{}
fmt.Fprint(b, "0")
go func() {
time.Sleep(1 * time.Second)
for i := 1; i < 4; i++ {
fmt.Fprint(b, i)
time.Sleep(1 * time.Second)
}
}()
scanner := bufio.NewScanner(b)
for scanner.Scan() {
log.Print(scanner.Text())
}
if err := scanner.Err(); err != nil {
log.Println("扫描时出现问题：", err)
}
期望的结果是：0123
实际结果是：0
我尝试了一个使用io.Pipe的版本
r, w := io.Pipe()
fmt.Fprint(w, "0")
go func() {
time.Sleep(1 * time.Second)
for i := 1; i < 4; i++ {
fmt.Fprint(w, i)
time.Sleep(1 * time.Second)
}
}()
scanner := bufio.NewScanner(r)
for scanner.Scan() {
log.Print(scanner.Text())
}
if err := scanner.Err(); err != nil {
log.Println("扫描时出现问题：", err)
}
结果：致命错误：所有goroutine都处于休眠状态-死锁！
英文:
I try to write a test to verify cli prompts, emulate user inputs in response to some program outputs.
How to make scanner.Scan wait for the rest of the writes?
What I have so far:
b := &bytes.Buffer{}
fmt.Fprint(b, "0")
go func() {
time.Sleep(1 * time.Second)
for i := 1; i < 4; i++ {
fmt.Fprint(b, i)
time.Sleep(1 * time.Second)
}
}()
scanner := bufio.NewScanner(b)
for scanner.Scan() {
log.Print(scanner.Text())
}
if err := scanner.Err(); err != nil {
log.Println("problem while scanning:", err)
}
Expected result is: 0123
Actual result is: 0
I tried a version with io.Pipe
r, w := io.Pipe()
fmt.Fprint(w, "0")
go func() {
time.Sleep(1 * time.Second)
for i := 1; i < 4; i++ {
fmt.Fprint(w, i)
time.Sleep(1 * time.Second)
}
}()
scanner := bufio.NewScanner(r)
for scanner.Scan() {
log.Print(scanner.Text())
}
if err := scanner.Err(); err != nil {
log.Println("problem while scanning:", err)
}
result: fatal error: all goroutines are asleep - deadlock!
答案1
得分: 0
使用管道时，写入和读取是同步的。没有匹配的读取操作，写入操作无法完成。将第一个写入操作移到goroutine中，并关闭管道的写入端，以允许扫描器停止扫描。
r, w := io.Pipe()
go func() {
defer w.Close()
fmt.Fprint(w, "0")
time.Sleep(1 * time.Second)
for i := 1; i < 4; i++ {
fmt.Fprint(w, i)
time.Sleep(1 * time.Second)
}
}()
scanner := bufio.NewScanner(r)
for scanner.Scan() {
log.Print(scanner.Text())
}
if err := scanner.Err(); err != nil {
log.Println("扫描时出现问题：", err)
}
英文:
When using a pipe, writes and reads are synchronous. A Write cannot complete without a matching Read. Move the first write into the goroutine. And Close the writing end of the pipe to allow the scanner to stop scanning.
r, w := io.Pipe()
go func() {
defer w.Close()
fmt.Fprint(w, "0")
time.Sleep(1 * time.Second)
for i := 1; i < 4; i++ {
fmt.Fprint(w, i)
time.Sleep(1 * time.Second)
}
}()
scanner := bufio.NewScanner(r)
for scanner.Scan() {
log.Print(scanner.Text())
}
if err := scanner.Err(); err != nil {
log.Println("problem while scanning:", err)
}
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