Jump to definition in HEEx templates

[katafrakt]

At @Jump-App one of the most longed for features in Expert was ability to jump to definition in HEEx templates, when clicking on components. This works in cases like this:

~H"""
<MyComponents.my_button>Submit</MyComponents.my_button>
"""

... but not when using a "shorthand notation", i.e.:

import MyComponents

~H"""
<.my_button>Submit</.my_button>
"""

The reason why the former works is IIRC because ElixirSense interprets MyComponenets.my_button correctly as a function call, but obviously .my_button cannot be interpreted like a correct Elixir code.

I made a change to Expert that adds a "normalization" step for contents of ~H sigil, which detects the shorthand notation and replaces it as my_button(assigns) before sending to ElixirSense. You can see the change here (this is a PR against my fork). We released Expert binaries with this change internally and several people reported go to definition working just fine with it.

Now, we would like to upstream it. But I do know that this is a bit of a hacky change, so I want to discuss it first. Perhaps there is a better way to explore? Perhaps compiling contents of the sigil Phoenix.LiveView.TagEngine would be a better approach, but then it would require some kind of plugin system, to only activate it when LiveView is actually present.

Do you have any thoughts on this?

[doorgan]

Some thoughts:

• I think more generally that we don't have a very good plugin architecture, and this change coming from a third party library does sound like it'd be best as a plugin. But we don't have that right now, and it requires quite a bit of heavy lifting.

• Another thought relating the implementation is that we probably should only apply this to ~H sigils if liveview is available and sigil_h is imported.

I created #270 to track the first point. I'm on the fence about the changes you suggest from your PR: it makes practical sense in the short term, but long term I'm not sure it's the direction we'd like to take, we need better plugin/integration support.

[katafrakt]

Thanks for sharing your thoughts!

I can wrap my changes in LiveView presence detection, however this probably will make it very hard to test both cases - with LiveView present and absent. Unless there's some way to do it I'm not aware of (?).

[doorgan]

We have a bunch of fixture projects here: https://github.com/elixir-lang/expert/tree/main/apps/forge/test/fixtures
I think you could create a project with liveview as a dependency and one without it, then test the completions for both.
We kinda do that already to test that we don't pollute the project completions with Expert dependencies among other things.

[katafrakt]

Ah, this is nice. Thanks for pointing me to it. I'll address this and will make a pull request then.