Use insertFinalNewline option from editorconfig for Handlebars / Ember files

[dcyriller]

Description

By default, Prettier will remove the final newline from Handlebars / Ember files. Why? Because otherwise it would add an extra DOM text node and in most cases this would be unnecessary. This is the recommended practise in the Ember ecosystem (source).

In this PR I propose a small adjustement to this default behavior. Prettier would read insertFinalNewline option from editorconfig (for Handelbars / Ember files only). When the option is set to true, Prettier would add a final newline. When set to false, the final newline would be removed.

This PR is still a draft. Indeed I'd like this option to be read only from editorconfig (not user configurable). But I don't know how to do that and I would have to spend some time on it. So, I prefer to discuss the PR first not to engage too much work in case you don't want to go down that path. May you let me know if you are okay with the direction it is taking?

Links

• a PR (closed) to add final newlines
• related discussion

Checklist

• I’ve added tests to confirm my change works.
• (If changing the API or CLI) I’ve documented the changes I’ve made (in the docs/ directory).
• (If the change is user-facing) I’ve added my changes to changelog_unreleased/*/XXXX.md file following changelog_unreleased/TEMPLATE.md.
• I’ve read the contributing guidelines.

✨Try the playground for this PR✨

[thorn0]

It's difficult to agree with the Ember team's reasoning about doing the newline stripping on the editor's side.

From ember-cli/ember-cli#3440 (comment):

That could break cases where a component's white-space is pre

Isn't this an edge case that happens really rarely though? Besides, it looks like the problem can be solved by putting a comment at the end of such a template to control how many significant trailing blank lines it should have.

content ...

{{! The two newlines before this comment should be preserved. The final newline after this comment shouldn't matter. }}

There are great points in ember-cli/ember-cli#3738

[fisker]

I alway like the idea repect editorconfig, not just handlebars. Every editor I use take precedence over editor settings, why shouldn't we?

[thorn0]

@fisker So are you okay with adding an option controlled only by EditorConfig?

[fisker]

Yes.

[thorn0]

That's an interesting solution to the "How do we add an option without adding an option?" problem. Need to think more about it.

[dcyriller]

Thank you for your feedbacks.

That's an interesting solution to the "How do we add an option without adding an option?" problem. Need to think more about it.

I'll try to think about it as well. If you have any pointer, it is welcome :)

[tylerbecks]

Any updates on this? I'm being affected and would love to see this merge!
This is the problem I'm having: ember-template-lint/ember-template-lint-plugin-prettier#100