Mix compiler integration for Roux languages.

Discovers source files, updates inputs, dispatches compile queries, and persists state across VM restarts via a manifest. The incrementality logic lives in Roux's validation pipeline — this module orchestrates the top-level compile flow, on a Roux.Session: the files are synced into the :source_text input by Roux.Sources (a file whose stamp held is not read; one rewritten with the same content changes nothing), and a run that changed nothing writes nothing.

Configuration

Add :roux to your project's compilers list and configure languages via the :roux key in project/0:

def project do
  [
    compilers: [:roux] ++ Mix.compilers(),
    roux: [
      languages: [MyLang, AnotherLang],
      source_dirs: ["lib", "src"]  # optional, defaults to ["lib"]
    ],
    # ...
  ]
end

Languages compiled after it

The compiler runs before :elixir, so the project's Elixir code can call what it compiles; but a language is Elixir code, and often the project's own, compiled by :elixir. It runs only languages compiled against this roux (Roux.Query.format/0): one not compiled yet (a cold build), or compiled against a roux of another definition format (an upgrade, after which Mix recompiles what uses roux), is compiled only once :elixir has run. When :elixir follows :roux in the project's compilers, the run waits for it (Mix.Task.Compiler.after_compiler/2), and compiles the sources then; a language still not ready then is an error. Otherwise a language not compiled yet compiles nothing, and one of another format is an error.