Petr

Petr

Would one-time self-replacing macro/compile-time-function instead of CLI generators be possible?

There is an example in Ash Framework of adding a resource Album into Music domain
mix ash.gen.resource Tunez.Music.Album --extend postgres. It generates a new module Album and modifies Music module – adding the Album into the domain.

I wondered if it would be possible to rather have a compile-time function (macro-ish) that would replace itself this one time during compilation and modify other modules as needed? It would allow developers not to deal with CLI but just use Elixir functions instead in the IDE environment having its usual features (docs, autocompletion, etc.)

To make it a bit more clear, I am imagining something like:

  • Add add_resource "Artist", extend: "postgres" in the defmodule Tunez.Music.
  • During compilation, add_resource would get called replacing itself and modifying Tunez.Music module, and creating Tunez.Music.Artist module
    • It would add resource Tunez.Music.Artist in the resources do ... block.
  • Which means it would have to recompile Tunez.Music after the function add_resource was executed and add Tunez.Music.Artist to the compilation queue.

What do I expect? To hear where this idea breaks down and to learn something new from that about Elixir. (Or possibly, how to achieve this.)

Why am I asking: I am exploring Elixir and its ecosystem and libraries (looks all very promising). I like to learn about languages/frameworks by trying to push at their limits. I would like to have the natural Elixir interface to generate the code instead of dealing with CLI tools myself.

If feasible, I would try to do this to get my hands dirty.

Thanks.

Most Liked

zachdaniel

zachdaniel

Creator of Ash

I think it would be technically doable, but would be relatively complex, and might be able to be done better via things like editor snippets etc. but yeah a macro could call arbitrary code at compile time, including code that replaces it in its own source file.

LostKobrakai

LostKobrakai

Wouldn’t even need to be a macro. When there’s no AST to be replaced with other AST it could potentially even be a function call. Though not sure how much “context” one gets about where exactly a call originated to replace that line.

Should also be quick to “validate”

# lib/commands.ex
Mix.Task.run("ash.gen.resource", ["Tunez.Music.Album", "--extend", "postgres"])

File.write(__ENV__.file, File.stream!(__ENV__.file, :line) |> Enum.at(-1))

Where Next?

Popular in Questions Top

itssasanka
Hi all, Trying to get some more clarity over utc_datetime and naive_datetime for Ecto: https://hexdocs.pm/ecto/Ecto.Schema.html#module-...
New
_russellb
I want to try my hand at web scraping. What tools/libraries do I need to use. I’m hoping to turn this into something professional so don’...
New
New
lastday4you
I wanted to check elixir version in phoenix because i found that my elixir is 1.5 but when i use Enum.chunk_by it said the function is un...
New
rms.mrcs
Hi, I need to transform a list of numbers into a map where the keys are the indexes and the values are the original values of the list....
New
alice
Hey, Just curious what are the main benefits of Elixir compared to Clojure? When is Elixir more useful than Clojure and vice versa? Th...
New
johnnyicon
Hi all, I've just started learning Elixir and Phoenix Framework, so please pardon my n00bness at this stage. I'm trying to use Postg...
New
baxterw3b
Hi guys, i’m new in the Elixir world, and i have to say, that i love it! i’m having some problem to understand anonymous functions with ...
New
chrisalley
ExUnit now has describe blocks which is a welcome addition coming from RSpec. In the docs, it states that nested hierarchies of describe ...
New
jay1
Why is it that the mnesia database isn’t the most preferred database for use in Elixir/Phoenix?
New

Other popular topics Top

JDanielMartinez
Hi! May someone helps me, please! I have two apps into an umbrella project: the first one is Database, which manages queries, and the se...
New
yurko
Here are few pieces of (common) Linux knowledge that we use for reasonably small one server apps. We use Ubuntu but this should work for ...
New
Tee
can someone please explain to me how Enum.reduce works with maps
New
_russellb
I want to try my hand at web scraping. What tools/libraries do I need to use. I’m hoping to turn this into something professional so don’...
New
nsuchy
Hi. I’ve noticed that Windows Powershell has it’s own IEX command and you cannot access Elixir’s IEX due to the conflict. This isn’t a cr...
New
aadeshere1
I have a another noob question about loop. Since elixir is immutable, while loop is not directly possible. total = 10 while total != 0 ...
New
fayddelight
I tried installing elixir 1.11.2 erlang 23.3.4 via asdf in my zsh shell. Enabled the versions locally and globally. When I list them ...
New
msaraiva
Surface is an experimental library built on top of Phoenix LiveView and its new LiveComponent API that aims to provide a more declarative...
564 42633 214
New
AstonJ
by Lance Halvorsen Elixir and Phoenix are generating tremendous excitement as an unbeatable platform for building modern web application...
460 27162 124
New
magnetic
Hey :wave:t3: Elixir community, I’ve been learning Elixir, and working on some side projects. My editor of choice is VSCode, and althoug...
New

We're in Beta

About us Mission Statement