Is there a Go implementation of fs.ReadDir for Google Cloud Storage?

I am creating a web application in Go.

I have modified my working code so that it can read and write files on both a local filesystem and a bucket of Google Cloud Storage based on a flag.

Basically I included a small package in the middle, and I implemented my-own-pkg.readFile or my-own-pkg.WriteFile and so on...

I have replaced all calls in my code where I read or save files from the local filesystem with calls to my methods.

Finally these methods include a simple switch case that runs the standard code to read/write locally or the code to read/wrote from/to a gcp bucket.

My current problem
In some parts I need to perform a ReadDir to get the list of DirEntries and then cycle though them. I do not want to change my code except for replacing os.readDir with my-own-pkg.ReadDir.

So far I understand that there is not a native function in the gcp module. So I suppose (but here I need your help because I am just guessing) that I would need an implementation of fs.FS for the gcp. It being a new feature of go 1.6 I guess it's too early to find one.

So I am trying to create simply a my-own-pkg.ReadDir(folderpath) function that does the following:

1. case "local": { <readdir as usual>}
2. case "gcp": {

<Use gcp code sample to list objects in my bucket with Query.Prefix = folderpath and
Query.Delimiter="/"

Then create a slice of my-own-pkg.DirEntry (because fs.DkrEntry is just an interface and so it needs to be implemented... ) and return them.

In order to do so I need to implement also the interface fs.DirEntry (which requires the implementation of interface for FileInfo and maybe something else...)

Question 1) is this the right path to follow to solve my issue or is there a better way?

Question 2) (only) if so, does the gcp method that lists object with a prefix and a delimiter return just files? I can't see a method that returns also the list of prefixes found

(If I have prefix/file1.txt and prefix/a/file2.txt I would like to get both "file1.txt" and "a" as files and prefixes...)

I hope I was enough clear... This time I can't include code because it's incomplete... But in case it helps I can paste what I can.

NOTE: by the way go 1.6 allowed me to solve elegantly a similar issue when dealing with assets either embedded or on the filesystem thanks to the existing implementation of fs.FS and the related ReadDirFS. So good if I could follow the same route 🙂

By the way I am going on studying and experimenting so in case I am successful I will contribute as well

I think your abstraction layer is good but you need to know something on Cloud Storage: The directory doesn't exist.

In fact, all the object are put at the root of the bucket / and the fully qualified name of the object is /path/to/object.file. You can filter on a prefix, that return all the object (i.e. file because directory doesn't exist) with the same path prefix.

It's not a full answer to your question but I'm sure that you can think and redesign the rest of your code with this particularity in mind.