OCaml: Handle some edge cases; refactor parser, main.ml; add config fetcher

ocaml/lib/checks/checks.ml

@@ -0,0 +1,22 @@
+open Utilities.Aliases
+
+(*
+   The purpose of this module is to run multiple checks at appropriate times.
+   All functions should end with a call to exit, which will print error messages
+   and quit with code schema.meta.status if schema.meta.error_level is Fatal.
+
+   When adding checks, consider that the error message will be overriten if exit
+   is not called between schema changes. This should be improved later so that a
+   list instead is printed entirely by exit, and then emptied.
+*)
+
+let exit (schema: Schema.schema): Schema.schema =
+    if schema.output.main <> "" then print_endline schema.output.main;
+    if schema.output.log <> "" then elog schema.output.log;
+    if schema.meta.error_level == Fatal then exit schema.meta.status
+    else schema
+
+let post_config (schema: Schema.schema): Schema.schema =
+    System.Process.Su.is_executable schema
+    |> exit
+