Unable to "chain" BasePathFs

[francoishill]

This example does not work as expected:

package main

import (
    "fmt"

    "github.com/spf13/afero"
)

func main() {
    fs1 := afero.NewBasePathFs(afero.NewOsFs(), "/dir1/subdir1")
    fmt.Println(fs1.(*afero.BasePathFs).RealPath("file.txt"))
    fs2 := afero.NewBasePathFs(fs1, "/dir2/subdir2")
    fmt.Println(fs2.(*afero.BasePathFs).RealPath("file.txt"))
}

The above output is:

/dir1/subdir1/file.txt
/dir2/subdir2/file.txt

Instead I expected fs2 to have nested paths as it uses fs1 as its source:

/dir1/subdir1/file.txt
/dir1/subdir1/dir2/subdir2/file.txt

[vetinari]

If the example would print the nested path, an app which just gets the fs2 from your example above, would be able to reveal too much about the system, IMO.
If all agree to extend the RealPath() to check for the base's type and call then that RealPath(), I can add it (@spf13 , @mbertschler please :))

[francoishill]

Your point makes sense. The problem, however, is that the RealPath method is used by all other api methods (like Mkdir, Open, etc). Regarding your concern, perhaps make the RealPath method private?

Before reading your comment I did however implement pull request 80 to resolve this.

[mbertschler]

Hmm... #80 looks nice and works, but the security issue is probably also a valid point. Maybe we could leave the RealPath() behaviour like this, but add a private fullPath() method that works like in your pull request and then replace all internal usages of RealPath() with this?

[francoishill]

Sure, I like that