YAML with a sequence containing varying types causes parse failure, but does not return error

[tonglil]

For some odd reason, this code fails depending on the content of the yaml file.

Code:

package main

import (
	"fmt"
	"os"

	"gopkg.in/urfave/cli.v1"
	"gopkg.in/urfave/cli.v1/altsrc"
)

var build = "0" // build number set at compile-time

func main() {
	app := cli.NewApp()
	app.Name = "fails"
	app.Version = fmt.Sprintf("0.1+%s", build)
	app.Action = run
	app.Flags = []cli.Flag{
		cli.StringFlag{
			Name: "file",
		},
		altsrc.NewStringSliceFlag(cli.StringSliceFlag{
			Name: "surrogate-keys",
		}),
	}

	app.Before = altsrc.InitInputSourceWithContext(app.Flags, altsrc.NewYamlSourceFromFlagFunc("file"))

	app.Run(os.Args)
}

func run(c *cli.Context) {
	fmt.Println("test")
	fmt.Println(c.StringSlice("surrogate-keys"))
}

yaml file that breaks the app:

---
surrogate-keys:
  - x
  - y
  - z

yaml file that works:

---
surrogate-keys:
  - xx
  - yy
  - zz

[jszwedko]

Hi @tonglil,

This one surprised me. Apparently an unquoted y is a boolean value in YAML 1.1 (see go-yaml/yaml#214 for more discussion), so, in this case, the YAML is parsed as map[surrogate-keys:[x true z]] which doesn't fit in a StringSlice.

This should fail with a better error during parsing though, so I'll update the title and mark as a bug.

[tonglil]

Thanks.
Yeah that was really strange to me while I was trying to debug why my app wasn't taking flags.

[coilysiren]

Hiya! There's a known issue with the current implementation of the CLI, where altsrc is generally clunky and poorly documented. My current idea is that I'm going to move all of the altsrc functionality into the main package in some way, and that's how all of the "altsrc is weird and different???" issues people are having will get resolved. I'm tracking that work here => #833