Weird behavior when mixing backends

[waltton]

Some examples of the weird behavior when mixing flag and envvar:

❌ bar default overwrite bar value from envvar

$ BAR=bar-envvar ./test-confita -foo=foo-flag
2019/09/29 10:24:37 cfg.Foo: 'foo-flag'
2019/09/29 10:24:37 cfg.Bar: 'bar-default'

✅ foo value from envvar it's overwritten by flag as expected

$ FOO=foo-envvar ./test-confita -foo=foo-flag
2019/09/29 10:29:22 cfg.Foo: 'foo-flag'
2019/09/29 10:29:22 cfg.Bar: 'bar-default'

❌ foo keeps the value from envvar ignoring the flag

$ BAR=bar-envvar FOO=foo-envvar ./test-confita -foo=foo-flag
2019/09/29 10:25:33 cfg.Foo: 'foo-envvar'
2019/09/29 10:25:33 cfg.Bar: 'bar-envvar'

go code:

package main

import (
	"context"
	"log"

	"github.com/heetch/confita"
	"github.com/heetch/confita/backend/env"
	"github.com/heetch/confita/backend/flags"
)

type Config struct {
	Bar string `config:"bar"`
	Foo string `config:"foo"`
}

func main() {
	cfg := Config{
		Bar: "bar-default",
	}

	loader := confita.NewLoader(
		env.NewBackend(),
		flags.NewBackend(),
	)

	err := loader.Load(context.Background(), &cfg)
	if err != nil {
		panic(err)
	}

	log.Printf("cfg.Foo: '%s'\n", cfg.Foo)
	log.Printf("cfg.Bar: '%s'\n", cfg.Bar)
}

[steamrolla]

Can you post the version of confita you are using from go.mod?

[waltton]

I'm using v0.8.0

[tealeg]

We're slowly working on a bit of a redesign of confita that might address some of these issues.

[zoido]

It seems like it caused by

confita/backend/flags/flags.go

Lines 143 to 149 in 86d03df

	func isFlagSet(config *confita.FieldConfig) bool {
	flagset := make(map[*confita.FieldConfig]bool)
	flag.Visit(func(f *flag.Flag) { flagset[config] = true })
	_, ok := flagset[config]
	return ok
	}

If I read it well, the implementation causes that when one flag is set isFlagSet is true for any input and therefore for all of the config values.

@waltton's 1st case is then cased by the fact that default values are used as defaults for the flag definitions

@tealeg Is it worth to try to fix this in the current state in the context of the mentioned upcoming redesign?