Add support for case and when tags

[charlespwd]

In this PR

• Add support for case tag
• Add support for when tag

Decisions

• Never break case
• Only break when when the undocumented comma or or syntax is used
  • Same way as the others

Examples

It should break and indent when statements, and not break the when
printWidth: 1
{% case candy.type %}
  {% when 'gummy bears' %}
    yum!
  {% else %}
    ok!
{% endcase %}

It should break on when comma syntax
printWidth: 1
{% case candy.type %}
  {% when 'gummy bears',
    'chocolate'
  %}
    yum!
  {% else %}
    ok!
{% endcase %}

It should break on when or syntax (and prefer commas)
printWidth: 1
{% case candy.type %}
  {% when 'gummy bears',
    'chocolate',
    'chips'
  %}
    yum!
  {% else %}
    ok!
{% endcase %}

[karreiro]

Thank you, @charlespwd! I've left only one minor/optional comment :)

[karreiro]

I wonder if users would prefer something like this:

Suggested change

	{% case candy.type %}
	{% when 'gummy bears',
	'chocolate',
	'chips'
	%}
	{% case candy.type %}
	{% when 'gummy bears',
	'chocolate',
	'chips'
	%}

[charlespwd]

I think that happens in languages like python and ruby but is really frowned upon in front-end communities (never seen it in JS, CSS, TS). I did see it in clojure/clojurescript but it takes a good editor plugin to handle it properly. Trying to do that manually is a PITA.

I feel like you should be able to manually indent your code reasonably and that feels hard. It's 4 tabs in! And if you use {%-, that'd be 4 tabs + 1 space.

😬