Enable FileSystemProvider to stat a file as readonly

[gjsjohnmurray]

Currently a FileSystemProvider can register as readonly, meaning that every file it provides is opened in a readonly editor. This is nice, but even better if the FileStat it returns from its stat() method had an optional readonly property. Then I think this line could easily treat a true readonly value as a signal to set isReadonly true. @bpasero what do you think?

[bpasero]

I think this is generally a nice idea, but I am worried that it will make file operations very complicated: imagine a folder where just a few files are readonly. Now a fs operation runs that operates on all files in the folder, not just one (e.g. rename of the folder? delete?). Naturally with this we would first have to ask the provider if any of the files that are potentially modified are readonly before even starting the operation, which seems quite crazy to me.

[gjsjohnmurray]

Fair point, but what happens at the moment in such scenarios if the user has set restrictive OS-level file permissions to protect just a few of the files in a folder tree? Does VSCode already run a preflight check on, say, a parent folder delete and decline to start the operation if any of the descendant files isn't deletable?

[bpasero]

@gjsjohnmurray yeah we are not doing anything but rely fully on the OS to do the right thing. If one file in a folder is write protected, the OS may decide that a rename on the parent folder is not possible (have not validated that).

[gjsjohnmurray]

@bpasero I'd also argue that it shouldn't be VSCode's responsibility to recursively check the readonly stat of every file within a folder before asking the FileSystemProvider to delete the folder. The FSP is best placed to know if that's an appropriate check to make. For example my FSP might simply fail the folder delete request immediately because it's a root folder. I certainly don't want you to have wasted time (yours and mine) walking the entire tree and asking me to stat each file for you if I'm always going to reject your subsequent request to delete the root folder.

[bpasero]

@gjsjohnmurray yeah good point 👍