为什么 Cobra 标志在此代码中不起作用

Question

How to get flags to work in Cobra using Local flags

package main

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

func main() {
    myCmd := &cobra.Command{
        Use: "myaction",
        Run: func(cmd *cobra.Command, args []string) {
            if len(args) == 1 {
                flags := cmd.Flags()
                var strTmp string
                flags.StringVarP(&strTmp, "test", "t", "", "Source directory to read from")
                fmt.Println(strTmp)
            }
        },
    }

    myCmd.Execute()
}

Error

go run main.go myaction --test="hello"
Error: unknown flag: --test
Usage:
  myaction [flags]

Flags:
  -h, --help   help for myaction

Answer 1

The Run part of the command gets executed only after the Execute is called on the command (you can also have a prerun-hook .)

So in your case when execute is called the runtime doesn't know about the flag. We should add the flags before the Execute is called on the command to make the runtime aware of it.

Code

package main

import (
    "fmt"

    "github.com/spf13/cobra"
)

func main() {
    var strTmp string
    myCmd := &cobra.Command{
        Use: "myaction",
        Run: func(cmd *cobra.Command, args []string) {
            if len(args) == 1 {
                fmt.Println(strTmp)
            }
        },
    }
    myCmd.Flags().StringVarP((&strTmp), "test", "t", "", "Source directory to read from")
    myCmd.Execute()
}

Output

⇒  go run main.go myaction --test "hello"
hello

But there is an alternate solution to this, when you want to add the flags based on a condition. You can set DisableFlagParsing to true and parse it later.

Code

package main

import (
    "fmt"

    "github.com/spf13/cobra"
)

func main() {
    myCmd := &cobra.Command{
        Use: "myaction",
        RunE: func(cmd *cobra.Command, args []string) error {
            if len(args) > 1 {
                flags := cmd.Flags()
                var strTmp string

                // Add the flag
                flags.StringVarP(&strTmp, "test", "t", "", "Source directory to read from")
                
                // Enable the flag parsing
                cmd.DisableFlagParsing = false

                // Parse the flags
                if err := cmd.ParseFlags(args); err != nil {
                    return err
                }

                fmt.Println(strTmp)
            }

            return nil
        },
    }

    // Disable flag parsing
    myCmd.DisableFlagParsing = true
    myCmd.Execute()
}

Output

⇒  go run main.go myaction --test "hello"
hello