Add support for linting ECR files

[nobodywasishere]

Requires Crystal >= 1.15.0. Lints ECR files by default. Closes #509

[Sija]

Specs would be good to have too 🙏

[veelenga]

@nobodywasishere I may have missed some conversation, but does this conflict with Lint/UselessAssign?

[nobodywasishere]

I don't know if there's been a conversation about that, but I do see how this could conflict with Lint/UselessAssign. As ECR files are expanded as Crystal code in-place, this can lead to stuff like this:

def render_page
  my_var = 1
  # ^^^^ error: Useless assignment to `my_var`
  render("path/to/page.ecr")
end

<%= my_var %>

This is already an issue though without this PR. Is there something specific you had in mind?

Another one specific to ECR though is something like:

<%
  my_var ||= 2
  # ^^^^ Lint/Syntax: Cannot use `my_var` in assignment to `my_var`
%>
<%= my_var %>

Which means templates just need to be written in a way where they're parsable outside the context of where they're rendered.

---

One cool thing I found while testing is that Lint/UnusedLiteral works:

<% 
  "hello world" 
  # ^^^^^^^^^^^ error: unused literal
%>

So it will give a warning if you accidentally leave off the =.

[nobodywasishere]

I've gone through all the rules and all the current auto corrections should be fine. Anything that changes stuff over the <% / %> boundary though would be a problem. For example, if there was a rule that commented out the contents of an if for some reason:

Original ECR:

<% if true %>
  <%= "hello" %>
<% end %>

Parsed ECR (without loc pragmas):

if true
  __str__ << "\n  "
  ("hello").to_s(__str__)
  __str__ << "\n"
end

"Corrected" source:

if true
  # __str__ << "\n  "
  # ("hello").to_s(__str__)
  # __str__ << "\n"
end

Could completely break or mangle the original ECR. This shouldn't be a problem with the current rules though.

[Sija]

By specs I meant testing the ECR support, not adding tests to the rule specs.

[nobodywasishere]

I thought having some tests that ensure functionality within an ECR file would be useful, but I can remove them if desired.

[veelenga]

lgtm

[Sija]

This needs another go-around, see https://github.com/crystal-ameba/ameba/actions/runs/12782021496/job/35630866247#step:7:1

[nobodywasishere]

I've no idea what caused that that wouldn't also work locally... I can try moving the location of the require "ecr/processor" to see if that'd work, but other than that unless it's building using an older version of Crystal (<1.15), I've no idea.

[nobodywasishere]

Yeah alpine is still using Crystal 1.14 https://pkgs.alpinelinux.org/package/edge/community/x86_64/crystal