ConfigResolver / Luau::parseConfig should store location of resolved config alongside alias

[JohnnyMorganz]

I would like to start implementing alias resolution via .luaurc for Luau LSP.

We already use Luau::ConfigResolver from Luau.Analysis, so it seems like it would be best to continue using that. Luau LSP essentially replicates the same CliConfigResolver used for luau-analyze:

luau/CLI/Analyze.cpp

Line 193 in e8a7acb

struct CliConfigResolver : Luau::ConfigResolver

The problem right now, however, is that once we want to start resolving aliases, we do not have the correct location to resolve it relative to. The aliases RFC states (https://github.com/luau-lang/rfcs/blob/master/docs/require-by-string-aliases.md):

if an alias is bound to a relative path, the path will be evaluated relative to the .luaurc file in which the alias was defined.

However this location is not preserved via Luau::parseConfig, making the Config datastructure unsuitable for alias resolution in analyse.

The Luau REPL does not seem to have this issue because it decides to implement its own recursive config resolution, and ends up storing and later referencing lastSearchedDir:

• luau/CLI/Require.cpp

  Line 256 in e8a7acb

  void RequireResolver::parseNextConfig()

• luau/CLI/Require.cpp

  Line 253 in e8a7acb

  return resolvePath(config.aliases[alias], joinPaths(lastSearchedDir, Luau::kConfigName));

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As an aside, do you folks intend to support the new require-by-string + aliases in luau-analyze soon? I imagine you will hit this same issue once you do so.