[PATCH] Add a VFSFromYAML class and a parser to create it

[Argyrios Kyrtzidis]

On Feb 20, 2014, at 10:02 AM, Ben Langmuir <blangmuir at apple.com> wrote:

> 
>> I think it is better to move the YAML VFS description to a new file under 'docs/'. This file format is API, and should be documented.
> 
>  Can this wait until we have more practical experience with the file format? Things in docs/ tend to have better documentation that what I've written here, and I don't want to put a lot of effort into this until we're sure this is the right format.

+1, we are far from the point of committing to API, this is still in flux.

> 
>> Unrelated to this patch, but how do we keep track of the current working directory? Or we don't just yet?
> 
>  We don't :)  I'll look at whether that is simple to do now, or can wait.  It won't be exercised until we use the VFS outside of FileManager, since FileManager always creates absolute paths I think.

FileManager has FileSystemOptions which has the “-working-directory” option, we should probably take advantage of that.

> 
> ================
> Comment at: lib/Basic/VirtualFileSystem.cpp:260
> @@ +259,3 @@
> +/// Possible configuration settings are
> +///   'case-sensitive': <boolean>
> +///
> ----------------
> Dmitri Gribenko wrote:
>> Is it optional?  If so, what is the default?
>> 
>> Please also add a mandatory version field, and refuse to load files with incorrect version.  I hope we will never have to bump the version and evolve the format in a compatible way, but who knows...
> It is optional, which is mentioned above.  I will specify its default value.
> 
> The version is going to make my unit tests ugly, but I see your point.

Do we need something standard at the beginning (something equivalent to a "<?xml version="1.0" encoding="UTF-8”?>”) that we can sniff out to figure out if it is json or binary format ?
I would prefer that if we move to binary format, the build system would need no changes at all (e.g. not require that the build system changes the file extension).