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vfs is GO library to support Virtual Filesystems. It provides the basic abstractions of filesystems and implementations, like:

• OS accessing the file system of the underlying OS,
• memfs a full filesystem in-memory, and
• dummy which does nothing other than outputting what file operation was called without actually modifiying the underlying file system.

$ go get github.com/lordofscripts/vfs

Note: Always vendor your dependencies or fix on a specific version tag.

import github.com/lordofscripts/vfs

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// Create a vfs accessing the filesystem of the underlying OS
var osfs vfs.Filesystem = vfs.OS()
osfs.Mkdir("/tmp", 0777)
// Make the filesystem read-only:
osfs = vfs.ReadOnly(osfs) // Simply wrap filesystems to change its behaviour
// os.O_CREATE will fail and return vfs.ErrReadOnly
// os.O_RDWR is supported but Write(..) on the file is disabled
f, _ := osfs.OpenFile("/tmp/example.txt", os.O_RDWR, 0)
// Return vfs.ErrReadOnly
_, err := f.Write([]byte("Write on readonly fs?"))
if err != nil {
 fmt.Errorf("Filesystem is read only!\n")
}

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// Create a fully writable filesystem in memory
mfs := memfs.Create()
mfs.Mkdir("/root", 0777)
// Create a vfs supporting mounts
// The root fs is accessing the filesystem of the underlying OS
fs := mountfs.Create(osfs)
// Mount a memfs inside /memfs
// /memfs may not exist
fs.Mount(mfs, "/memfs")
// This will create /testdir inside the memfs
fs.Mkdir("/memfs/testdir", 0777)
// This would create /tmp/testdir inside your OS fs
// But the rootfs `osfs` is read-only
fs.Mkdir("/tmp/testdir", 0777)

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// Now use a BitBucket Filesystem in Silent mode
fsb1 := bucketfs.Create()
fsb1.Mkdir("/bucket/testdir", 0777))
// Or an extended BitBucket Filesystem
ErrCustom := errors.New("A BitBucket error"))
fsb2 := bucketfs.CreateWithError(ErrCustom).
 WithFakeDirs([]string{"/bucket/Dir1", "/bucket/Dir2"}).
 WithFakeFiles([]string{"/bucket/Dir1/test.doc", "/bucket/Dir2/test.pdf"})
entries, err := fsb2.ReadDir("/bucket")

Check detailed examples below. Also check the GoDocs. The BucketFS can also be made read-only in the same manner as the first example above. See Detailed documentation about BucketVFS.)

• It has much more functionality than any of its predecessors. This is not a YAUF (Yet-Another-Useless-Fork))
• Pure unadulterated GO
• (Nearly) Fully tested
• Easy to create your own filesystem
• Mock a full filesystem for testing (or use included memfs or bucketfs)
• Compose/Wrap Filesystems ReadOnly(OS()) and write simple Wrappers
• Flexible BitBucket filesystem

Many features, see GoDocs and examples below

• OS Filesystem support
• ReadOnly Wrapper
• DummyFS for quick mocking
• MemFS - full in-memory filesystem
• MountFS - support mounts across filesystems

While the functionality is quite stable and heavily tested, interfaces are subject to change.

You need more/less abstraction? Let me know by creating a Issue, thank you.

The original author Benedikt Lang wrote:

I simply couldn't find any lib supporting this wide range of variation and adaptability.

And I (LordOfScripts) share his thoughts. In fact, I evaluated several similar GO libraries but many were too bloated and included other appendages I was not interested in. I loved this VFS version because it had no other dependencies.

The original GO-VFS repository was github.com/blang/vfs by Benedikt Lang). Which stopped at v1.0.0 about nine (9) years ago. It was a quite mature implementation which I was actually using in one of my projects. But it came short in emulating a Dry Run. I ended up writing my own quick & grey Dry Run for that purpose, and it worked quite well.

Since I was still using blang/vfs in the Unit Tests (only), I figured I might as well invest some time and integrate it fully to replace my Dry Run as a mere exercise. I started looking for better-fitting alternatives. There were none, but there were about 50+ forks of the original blang/vfs but all where just abandoned forks with no extra commits (people's fake trophies?). In that long list I came across the single fork that had actually extra commits and extra functionality.

So, I discovered 3JoB's fork tagged wrongly v1.0.0 when it should have been v1.1.0 because it built on the original with added functionality:

• Support for Symbolic Links
• Support for Walk function
• Minor changes like using any instead of interface{}

But 3JoB/vfs's version didn't quite meet my requirements. While the original version dated from 9 years ago, 3JoB's last commit was a year ago, but it seemed to have ended there too. I decided to fork that and enhance it:

Is this a YAUF (Yet-Another-Useless-Fork)? well, no! I plan on making certain enhancements that would make it suitable for my application out-of-the-box without the need for glue structures. So, Keep tuned! But to start with:

• Updated it to use main as branch instead of the deprecated master
• Added go.mod
• Included a GO workflow for building.
• Has a flexible BitBucket Filesystem bucketfs more suitable for testing
• Bumped version to v1.2.0 to properly reflect new functionality beyond Benedikt's & 3JoB's.

In due time more changes will come.

See LICENSE file.