feat: introduce convenience methods into MockFileSystem

[rcdailey]

• AddEmptyFile() added which is a convenience wrapper for AddFile() with an empty MockFileData.
• AddFile() overload added which consumes an IFileInfo.
• AddDirectory() overload added which consumes an IDirectoryInfo.
• GetFile() overload added which consumes an IFileInfo.

Unit test added for AddEmptyFile() but not the others, as the test code for them would have very little value.

Fixes TestableIO/System.IO.Abstractions.Extensions#32

[rcdailey]

I realize the PR title workflow is failing, however I would like the project maintainers to introduce whatever prefix they deem appropriate when they squash merge my PR into the mainline. Thank you.

[vbreuss]

Just a quick question from my side:
In TestableIO/System.IO.Abstractions.Extensions#32 you discussed adding it as extension methods to a separate library or adding it directly to the MockFileSystem.

Why not add it as extension methods in this repository?

[rcdailey]

Just a quick question from my side: In TestableIO/System.IO.Abstractions.Extensions#32 you discussed adding it as extension methods to a separate library or adding it directly to the MockFileSystem.

Why not add it as extension methods in this repository?

I didn't see a reason to add them as extension methods. Typically I only do that when I do not have access to the class in question. However, in my mind at least, the entire point of contributing these upstream (into this repo) was to make them a part of the class. I already have these as extension methods in my own code base and they were working fine.

I'm unfamiliar with any design policies or preferences in this repo or of its its maintainers, so I went about this using my own judgement. Is there a problem with having them in the class itself?

[vbreuss]

Just a quick question from my side: In TestableIO/System.IO.Abstractions.Extensions#32 you discussed adding it as extension methods to a separate library or adding it directly to the MockFileSystem.
Why not add it as extension methods in this repository?

I didn't see a reason to add them as extension methods. Typically I only do that when I do not have access to the class in question. However, in my mind at least, the entire point of contributing these upstream (into this repo) was to make them a part of the class. I already have these as extension methods in my own code base and they were working fine.

I'm unfamiliar with any design policies or preferences in this repo or of its its maintainers, so I went about this using my own judgement. Is there a problem with having them in the class itself?

@rcdailey :
Please don't get me wrong. Your solution is fine and I think that the convenience methods are a nice addition here!

I am just curious, if there is a specific reason why you implemented it this way, as you had to adapt the IMockFileDataAccessor interface and add quite a lot of methods there. Normally I try to keep interface definitions as minimal as possible.
By adding your implementation as extension methods in this repository, the interface could remain smaller.

Are there disadvantages to extension methods that I am not aware of :-)

[rcdailey]

I added them to the interface because everything else seemed to have been added there. I honestly didn't think too hard about it. Should I remove them from there? For my own understanding, how do you decide between adding to the interface or not? Happy to learn & adjust. I am not too strongly opinionated on how I went about this. I'm relying on you fine folks to let me know how it should be done :-)

Thanks for the discussion!

[rcdailey]

For what it's worth, I have these already in my own project as a set of extension methods. I'm happy to drop them in here just like this if that's what you want. Code is here.

I think the reason I jumped right into making them part of the class was @fgreinacher's comment on the linked issue:

I'm also fine adding them to MockFileSystem.

Maybe I read that too literally. It's honestly not a big deal either way. Let me know how you'd like it done.

[fgreinacher]

I added them to the interface because everything else seemed to have been added there.

I'd also tend to add them to MockFileSystem directly for consistency. I don't see a lot of value introducing another class for these methods. But I might very well be missing something :)

[rcdailey]

I've force-pushed the requested changes and I've rebased onto latest changes in main.

[fgreinacher]

Looks good to me now, thanks for your work!

CI seems to be failing due to a .NET bug. We have to wait a bit until the fix is rolled out: dotnet/core#8194 (comment)

[github-actions]

This is addressed in release v19.2.1.