viper.ReadinConfig() errors with references to real filepath instead of only referencing in memory fs paths

[discentem]

Preflight Checklist

• I have searched the issue tracker for an issue that matches the one I want to file, without success.
• I am not looking for support or already pursued the available support channels without success.
• I have checked the troubleshooting guide for my problem, without success.

Viper Version

1.17.0

Go Version

1.21

Config Source

Files

Format

JSON

Repl.it link

https://replit.com/@kurtzbrandon/viperreadinconfigbug

Code reproducing the issue

package main

import (
	"errors"
	"fmt"
	"log"
	"path/filepath"

	"github.com/spf13/afero"
	"github.com/spf13/viper"
)

type Config struct {
	Version int `json:"version"`
}

func Load(fs afero.Fs, cfgDest ...*Config) error {
	// Defaults set here will be used if they do not exist in the config file
	viper.SetFs(fs)
	// Set up the config file details
	viper.SetConfigName("config")
	viper.SetConfigType("json")
	viper.AddConfigPath(".")
	viper.AddConfigPath(".viper")

	// Retrieve from EnvVars if they exist...
	viper.AutomaticEnv()

	// Read from the config file path
	err := viper.ReadInConfig()
	if err != nil {
		return fmt.Errorf("error with viper.ReadInConfig(): %w", err)
	}

	if cfgDest == nil {
		return errors.New("cfg cannot be nil")
	}

	return viper.Unmarshal(cfgDest[0])
}

func load(createFn func(fs afero.Fs, name string) (afero.File, error)) error {
	fs := afero.NewMemMapFs()

	err := fs.Mkdir(".viper", 0o777)
	if err != nil {
		return err
	}

	file, err := createFn(fs, ".viper/config")
	if err != nil {
		return err
	}

	cfg := Config{}

	_, err = file.Write([]byte(`{
		"version": 1
	   }`),
	)
	if err != nil {
		return err
	}
	file.Close()

	err = Load(fs, &cfg)
	if err != nil {
		return err
	}
	return nil
}

func main() {
	createWithAbsolute := func(fs afero.Fs, name string) (afero.File, error) {
		s, err := filepath.Abs(name)
		if err != nil {
			return nil, fmt.Errorf("createWithAbsolute failed: %w", err)
		}
		return fs.Create(s)
	}

	if err := load(createWithAbsolute); err != nil {
		log.Fatal(err)
	}
	fmt.Println("load with createWithAbsolute succeeded")
	createWithoutAbsolute := func(fs afero.Fs, name string) (afero.File, error) {
		return fs.Create(name)
	}

	if err := load(createWithoutAbsolute); err != nil {
		log.Fatal(err)
	}
	/*
		load with createWithAbsolute succeeded
		2023/10/22 21:54:33 error with viper.ReadInConfig(): Config File "config" Not Found in "[/Users/bk/project /Users/home/project/.viper]"
		exit status 1
	*/
	fmt.Println("load with createWithoutAbsolute succeeded")
}

Expected Behavior

The second call to load() with createWithoutAbsolute is expected to fail but it should not mention my real OsFs in the error message. Instead I expect the error message to only reference the in memory filesystem. It seems viper.ReadInConfig() has some fallback behavior maybe? If such behavior exists as a feature, fallback should be off by default.

Actual Behavior

2023/10/22 21:54:33 error with viper.ReadInConfig(): Config File "config" Not Found in "[/Users/bk/project /Users/home/project/.viper]"
exit status 1

The error message from viper.ReadInConfig() is referencing filepaths on my real OsFs even though I told viper to only read from in-mem

Steps To Reproduce

No response

Additional Information

No response

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