pathlib

pathlib

Inspired by Python's pathlib, made better by Golang.

pathlib is an "object-oriented" package for manipulating filesystem path objects. It takes many cues from Python's pathlib, although it does not strictly adhere to its design philosophy. It provides a simple, intuitive, easy, and abstracted interface for dealing with many different types of filesystems.

pathlib is currently in the alpha stage of development, meaning the API is subject to change. However, the current state of the project is already proving to be highly useful.

Table of Contents

• Examples
  • OsFs
  • In-memory FS
• Design Philosophy
  • filepath.Path
  • filepath.File
• Frequently Asked Questions
  • Why pathlib and not filepath?
  • Why not use afero directly?
  • Does this provide any benefit to my unit tests?
  • What filesystems does this support?

Examples

OsFs

Beacuse pathlib treats afero filesystems as first-class citizens, you can instantiate a Path object with the filesystem of your choosing.

Code

package main

import (
	"fmt"
	"os"

	"github.com/chigopher/pathlib"
	"github.com/spf13/afero"
)

func main() {
	// Create a path on your regular OS filesystem
	path := pathlib.NewPathAfero("/home/ltclipp", afero.NewOsFs())

	subdirs, err := path.ReadDir()
	if err != nil {
		fmt.Printf("%v\n", err)
		os.Exit(1)
	}

	for _, dir := range subdirs {
		fmt.Println(dir.Name())
	}
}

Output

[ltclipp@landon-virtualbox examples]$ go build .
[ltclipp@landon-virtualbox examples]$ ./examples | tail
Music
Pictures
Public
Templates
Videos
git
go
mockery_test
snap
software

In-memory FS

Code

package main

import (
	"fmt"
	"os"

	"github.com/chigopher/pathlib"
	"github.com/spf13/afero"
)

func main() {
	// Create a path using an in-memory filesystem
	path := pathlib.NewPathAfero("/", afero.NewMemMapFs())
	hello := path.Join("hello_world.txt")
	hello.WriteFile([]byte("hello world!"), 0o644)

	subpaths, err := path.ReadDir()
	if err != nil {
		fmt.Printf("%v\n", err)
		os.Exit(1)
	}

	for _, subpath := range subpaths {
		fmt.Printf("Name: %s Mode: %o Size: %d\n", subpath.Name(), subpath.Mode(), subpath.Size())
	}

	bytes, _ := hello.ReadFile()
	fmt.Println(string(bytes))
}

Output

[ltclipp@landon-virtualbox examples]$ go build
[ltclipp@landon-virtualbox examples]$ ./examples 
Name: hello_world.txt Mode: 644 Size: 12
hello world!

Design Philosophy

The design philosophy of this package is to be as thin of a layer as possible to existing community-standard packages, like io, afero, and os. Additional functionality is provided in consise and logical ways to extend the existing community APIs.

filepath.Path

The API of filepath.Path can be grouped into a few main categories:

1. github.com/spf13/afero.Fs wrappers: these are methods that have nearly identical signatures to afero.Fs, with the exception of the path string (which is stored in the pathlib.Path object itself. afero.Fs is an object that is meant to interact directly with the filesystem.
2. github.com/spf13/afero.Afero wrappers: these are methods that again have nearly identical signatures to afero.Afero. afero.Afero is a convenience object that provides higher-level behavior to the underlying afero.Fs object.
3. Filesystem-specific methods: these are methods that are implemented by some, but not all, of the afero filesystems. These methods may fail at runtime if the filesystem you provide does not implement the required interface.
4. Python's Pathlib-inspired methods: these are methods that are not implemented in the previous two steps, and that provide the power behind the object-oriented design.
5. github.com/chigopher/pathlib-specific methods: these are miscellaneous methods that are not covered by any of the previous categories. These methods are typically conveniences around methods in one of the previous categories.

filepath.File

filepath.File is intended to be a thin wrapper around afero.File. We avoid simply returning this interface on calls to Open() and OpenFile() (etc) because we want the ability to extend our API beyond what afero provides. So, we create our own File object which embeds afero.File, but might possibly contain further functionality.

Whoa whoa whoa, what is this afero nonsense?

github.com/spf13/afero is a package that provides an abstracted interface to the underlying filesystem API calls. pathlib uses this package for operating on the abstracted filesystem. This is powerful because it allows you to to use essentially any kind of filesystem that you want. Additionally, afero is a first-class-citizen in pathlib meaning that you can implement and explicitly provide your own afero object.

The basic diagram looks like this:

Frequently Asked Questions

Why pathlib and not filepath?

filepath is a package that is tightly coupled to the OS filesystem APIs and also is not written in an object-oriented way. pathlib uses afero under the hood for its abstracted filesystem interface, which allows you to represent a vast array of different filesystems (e.g. SFTP, HTTP, in-memory, and of course OS filesystems) using the same Path object.

Why not use afero directly?

You certainly could, however afero does not represent a filesystem object in an object-oriented way. It is only object-oriented with respect to the filesystem itself. pathlib is simply a thin layer on top of afero that provides the filesystem-object-orientation.

Does this provide any benefit to my unit tests?

Most certainly! pathlib allows you to create in-memory filesystems, which have the nice property of being automatically garbage collected by Golang's GC when they go out of scope. You don't have to worry about defering any Remove() functions or setting up temporary dirs in /tmp. Just instantiate a MemMapFs and you're good to go!

What filesystems does this support?

Currently only POSIX-style paths are supported.