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Unexpected "doubling" behavior when trying to test output
I am trying to write some unit tests for my kingpin.Application, to test things like help output. To do that, I build the application the same as I would in my real program, and redirect output to a buffer. I also apparently have to tell the app not to terminate the program (the test) whenever it encounters an error. But when I do all of these things, I notice that the Terminate callback is called multiple times (though only when I have a subcommand) and the expected output is duplicated.
Here is a small reproducible test case.
package main
import (
"bytes"
"fmt"
"gopkg.in/alecthomas/kingpin.v2"
)
func main() {
app := kingpin.New("test", "Test application.")
_ = app.Command("subcommand", "A subcommand.")
var buf bytes.Buffer
app.Writer(&buf)
app.Terminate(func(exitcode int) { fmt.Printf("terminate(%d)\n", exitcode) })
_, err := app.Parse([]string{"--help"})
fmt.Printf("Parse error: %v\n", err)
fmt.Printf("%s\n", buf.String())
}
Expected output:
terminate(0)
Parse error: command not specified
usage: test [<flags>] <command> [<args> ...]
Test application.
Flags:
--help Show context-sensitive help (also try --help-long and --help-man).
Commands:
help [<command>...]
Show help.
subcommand
A subcommand.
Actual output:
terminate(0)
terminate(0)
Parse error: command not specified
usage: test [<flags>] <command> [<args> ...]
Test application.
Flags:
--help Show context-sensitive help (also try --help-long and --help-man).
Commands:
help [<command>...]
Show help.
subcommand
A subcommand.
usage: test [<flags>] <command> [<args> ...]
Test application.
Flags:
--help Show context-sensitive help (also try --help-long and --help-man).
Commands:
help [<command>...]
Show help.
subcommand
A subcommand.
If there is a better way to do what I want to do, I'm all ears. But for now, this looks like a bug.
For me help this code
usage := ""
usageBuffer := bytes.Buffer{}
app := kingpin.New("test", "")
app.Terminate(func(int) {
usage = usageBuffer.String()
usageBuffer.Reset()
})
app.UsageWriter(&usageBuffer)
...
fmt.Println(usage)