I’m not sure what you mean by “fixed the mistake” WRT Igniter, but I think I was just wrong when explaining our main use case with Spitfire. Sorry about that 
Error tolerance is why we use Spitfire.container_cursor_to_quoted/1 as opposed to Code.Fragment, but what we actually use Spitfire for is primarily Spitfire.Env.expand.
The way we are using it currently (and we aim to expand this usage) is, for example, when patching in a module name, we want it to respect existing module aliases.
For example, when installing AshPostgres, we make sure that your Repo module exists, is configured correctly, etc., and then we make sure that it is a child of your application (and that you have an application file, we create it if it doesn’t exist).
This patching logic is naive at the moment, but it will get more robust over time. I’ve also removed a bunch of stuff token this example simple
# in `Igniter.Project.Application`
def do_add_child(igniter, application, to_supervise) do
path = Igniter.Code.Module.proper_location(application)
Igniter.update_elixir_file(igniter, path, fn zipper ->
with {:ok, zipper} <- Igniter.Code.Module.move_to_module_using(zipper, Application),
{:ok, zipper} <- Igniter.Code.Function.move_to_def(zipper, :start, 2),
{:ok, zipper} <-
Igniter.Code.Function.move_to_function_call_in_current_scope(
zipper,
:=,
[2],
fn call ->
Igniter.Code.Function.argument_matches_pattern?(
call,
0,
{:children, _, context} when is_atom(context)
) &&
Igniter.Code.Function.argument_matches_pattern?(call, 1, v when is_list(v))
end
) do
zipper
|> Zipper.down()
|> Zipper.rightmost()
|> Igniter.Code.List.append_new_to_list(Macro.escape(to_supervise), diff_checker)
else
_ ->
{:warning, "...."}
end
end)
end
So when using append_new_to_list, that ultimately ends up using code that expands the environment at the place you are bringing in code, and uses that to
- honor aliases when checking for matches in the list
- use aliases when inserting a module into the AST
Error tolerance can be useful for us because it is theoretically possible to introduce invalid AST “temporarily” while working with igniter. You compose a bunch of AST modifiers, and I didn’t want to necessarily guarantee that, after every single modification you make, the AST is valid. Only when actually writing the file must it be valid.
If its not valid, though, you won’t get the nice features of being able to determine env at a location.
This is the entirety of our Spitfire usage currently.
@doc """
Expands the environment at the current zipper position and returns the
expanded environment. Currently used for properly working with aliases.
"""
def current_env(zipper) do
zipper
|> do_add_code({:__cursor__, [], []}, :after, false)
|> Zipper.topmost_root()
|> Sourceror.to_string()
|> String.split("__cursor__()", parts: 2)
|> List.first()
|> Spitfire.container_cursor_to_quoted()
|> then(fn {:ok, ast} ->
ast
end)
|> Spitfire.Env.expand("file.ex")
|> then(fn {_ast, _final_state, _final_env, cursor_env} ->
{:ok, struct(Macro.Env, cursor_env)}
end)
rescue
e ->
{:error, e}
end
