Filepath Walk bug?
During the development of a small project I noticed something strange with golang’s function filepath.Walk.
If you are going over a directory, and return filepath.SkipDir error on
a file entry. The walker will stop.
Setup directory
First, set up a simple directory to walk
mkdir -p foo/baz
touch foo/bar
touch foo/baz/qux
Run the script
Now, let’s run this example script, with the previous directory as the entry argument. I will reuse the example from golang documentation website with small changes.
package main
import (
"fmt"
"os"
"path/filepath"
)
func main() {
dir := os.Args[1] // this is not solid, but will work for the example
fileToSkip := "bar" // we skip on a file to highlight the bug
err := filepath.Walk(dir, func(path string, info os.FileInfo, err error) error {
if err != nil {
return err
}
if info.Name() == fileToSkip { // no check on entry type info.IsDir()
fmt.Printf("skipping a dir without errors: %+v \n", info.Name())
return filepath.SkipDir
}
fmt.Printf("visited file: %q\n", path)
return nil
})
if err != nil {
fmt.Printf("error walking the path %q: %v\n", dir, err)
}
}
This will output:
visited file: "foo"
skipping a dir without errors: bar
As you can notice, there’s no trace of subdir baz and file baz/qux.
Fix the script
To make this work “as expected” you will have to change line 17. With:
if info.IsDir() && info.Name() == fileToSkip { // now test on entry type
//unchanged
fmt.Printf("skipping a dir without errors: %+v \n", info.Name())
return filepath.SkipDir
}
Output is now:
visited file: "foo"
visited file: "foo/bar"
visited file: "foo/baz"
visited file: "foo/baz/qux"
So, next time using filepath.Walk be careful on this one!