Issue with object being nil in action function

[Crashk1d]

I'm not sure what has changed or why this isn't working but I was doing something similar in code about 2 years back.

I have the following sample struct with a Load() method that is a cli.BeforeFunc() (gonna simplify this greatly)

// Options encapsulates run time options coming from the cli and env
type Options struct {
	Host string
}

// Load is a cli before func used to inject cli options into the app context
func (o *Options) Load(app *cli.Context) error {
        o.Host = app.String("host")
	return nil
}

Then I have a top level command:

func Cmd(ctx context.Context) *cli.Command {
	return &cli.Command{
		Name:  "mycommand",
		Subcommands: []*cli.Command{
			MyCmd(ctx), 
		},
	}
}

Then I have a subcommand that will be using the options.

func MyCmd(ctx context.Context) *cli.Command {
        // here I instantiate my options struct
	options := &common.Options{}
	return &cli.Command{
		Name:   "foo",
		Before: options.Load,   // cli beforeFunc that loads cli options into my struct 
		Action: MyCmdAction(ctx, options),   // pass options to action function
		Flags:  myCommandFlags,
	}
}

func MyCmdAction(ctx context.Context, o *common.Options) func(app *cli.Context) error {
	return func(app *cli.Context) error {
		fmt.Printf("OPTIONS=%+v\n", o) // nil here
		return nil
	}
}

I have no idea why options is nil when passed to MyCmdAction(). Any ideas? I was doing stuff similar to this before.

[dearchap]

@rhugga Your sample code looks ok. I believe it should work. We've done some optimizations in urfave/cli since 2 years however all unit tests before those changes still pass. My guess is its the way the App.Run is called. Can you provide a complete sample with App initialization and when App.Run() is called ?

[dearchap]

@rhugga The following code based on your sample works as intended

package main

import (
	"context"
	"fmt"
	"os"

	"github.com/urfave/cli/v2"
)

// Options encapsulates run time options coming from the cli and env
type Options struct {
	Host string
}

// Load is a cli before func used to inject cli options into the app context
func (o *Options) Load(app *cli.Context) error {
	o.Host = app.String("host")
	return nil
}

func Cmd(ctx context.Context) *cli.Command {
	return &cli.Command{
		Name: "mycommand",
		Subcommands: []*cli.Command{
			MyCmd(ctx),
		},
	}
}

func MyCmd(ctx context.Context) *cli.Command {
	// here I instantiate my options struct
	options := &Options{}
	return &cli.Command{
		Name:   "foo",
		Before: options.Load,              // cli beforeFunc that loads cli options into my struct
		Action: MyCmdAction(ctx, options), // pass options to action function
	}
}

func MyCmdAction(ctx context.Context, o *Options) func(app *cli.Context) error {
	return func(app *cli.Context) error {
		fmt.Printf("OPTIONS=%+v\n", o) // nil here
		return nil
	}
}

func main() {
	a := &cli.App{
		Commands: []*cli.Command{
			Cmd(context.TODO()),
		},
		Flags: []cli.Flag{
			&cli.StringFlag{
				Name: "host",
			},
		},
	}

	a.Run(os.Args)
}

$ go run main.go --host hello mycommand foo 
OPTIONS=&{Host:hello}

I moved the flags to within the subcommand and that worked as well

$ go run main.go mycommand foo --host hello
OPTIONS=&{Host:hello}

So when you say it doesnt work is it possible you didnt specify the host flag on cmdline or maybe it was defined to pickup from the env ?