Problem when an argument is empty

[provCristianMaluenda]

Hi,
I am facing this issue. When an argument is empty, username in this case:
command --username $USERNAME --pwd $PWD
Cobra assigns --pwd to --username.
If both are required, the error says required flag(s) "pwd" not set.
The message is confused, and I don't understand why this happens.

---

Library versions:

github.com/spf13/cobra v0.0.3
github.com/spf13/pflag v1.0.3
github.com/spf13/viper v1.3.1

Regards,
Cristian.

[jharshman]

The message is confused, and I don't understand why this happens.

I'm not sure what you mean by this. The message required flag(s) "pwd" not set is correct because --username is being set to --pwd so it's requirement of being required is filled.

However, to address your primary issue, you can use "=" to ensure that the following flag is not read accidentally in the case of an empty value.

i.e:

command --username=$USERNAME --pwd=$PWD

[umarcor]

Alternatively, I think you can 'fix' it by using quotes around the variable, "$USERNAME", which is good practice regardless of cobra.

[provCristianMaluenda]

Thanks for the quick replay.
I tried using "=" and quote in the env var, but the validation doesn't work. In this case, Cobra considers the argument as empty ( "" ).
I think I can try to implement my own type.

[umarcor]

Do you mean that it fails because it does not accept an empty argument? Or that you cannot handle it because you need to tell apart a default empty and a user-provided empty?

[provCristianMaluenda]

It doesn't work because the flag exists but it is an empty string. So, the required validation doesn't work in this case. I have two options:

• Add a preRun function to validate the arguments
• Create a custom type.

[umarcor]

I cannot reproduce. See:

package main

import (
  "fmt"
  "os"
  "github.com/spf13/cobra"
)

func main() {
  if err := rootCmd.Execute(); err != nil {
    fmt.Println(err)
    os.Exit(1)
  }
}

// rootCmd represents the base command when called without any subcommands
var rootCmd = &cobra.Command{
  Use:   "test",
  Short: "A brief description of your application",
  Long: `A longer description...`,
  Run: func(cmd *cobra.Command, args []string) {
    fmt.Println(args)
  },
}

var Username string
var Password string

func init() {
  rootCmd.Flags().StringVarP(&Username, "username", "u", "default", "username (required)")
  rootCmd.Flags().StringVarP(&Password, "password", "p", "default", "password (required)")

  rootCmd.MarkFlagRequired("username")
  rootCmd.MarkFlagRequired("password")
}

root@91266ab2b8e1:/src/cobra/test# go run main.go    
Error: required flag(s) "password", "username" not set

root@91266ab2b8e1:/src/cobra/test# go run main.go -u user -p pass
[]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u user -p pass aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u -p pass aaa
Error: required flag(s) "password" not set

root@91266ab2b8e1:/src/cobra/test# go run main.go -u "" -p pass aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u= -p pass aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u= -p= aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u= -p "" aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u "" -p "" aaa
[aaa]

[jharshman]

@umarcor which version of cobra did you try to reproduce this with?
I notice that @provCristianMaluenda is using an older version. I haven't looked into it yet, but maybe a bug fix occurred between 0.0.3 and current 0.0.5

[provCristianMaluenda]

Thank @umarcor for your example.
This is the behavior that I think it is not desired.

root@91266ab2b8e1:/src/cobra/test# go run main.go -u= -p= aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u= -p "" aaa
[aaa]

root@91266ab2b8e1:/src/cobra/test# go run main.go -u "" -p "" aaa
[aaa]

For me, if I set an argument -p "" I would expect an Error: required flag(s) "password" not set. But, instead of an error, it continues the execution. So, in this case, the required is useless, and I need to validate the input in my code anyway.

[jharshman]

This is expected behavior.
https://godoc.org/github.com/spf13/cobra#Command.MarkFlagRequired

It guarantees the presence of the flag, not the argument.

[provCristianMaluenda]

You are right. My bad!
Thank guys for your help!

[jharshman]

No problem.

[umarcor]

@umarcor which version of cobra did you try to reproduce this with?

I used the latest master.

For me, if I set an argument -p "" I would expect an Error: required flag(s) "password" not set. But, instead of an error, it continues the execution. So, in this case, the required is useless, and I need to validate the input in my code anyway.

I think that this feature request makes sense, but not as the default behaviour for MarkFlagRequired. Either MarkFlagRequired could accept a RequireNonEmpty boolean argument, or another function could be added (say MarkRequiredNonEmpty). However, this deserves some care, as it is related to spf13/viper#276 (also spf13/viper#657).

Meanwhile, you can add a check in the initConfig function, just as it is done with cfgFile. I don't know how does this work with non-root commands, tho.