bug(handlebars): Idempotency issue

[dcyriller]

Description

<Textarea />

{{#if true}}
  Test
{{/if}}

is formatted to

<Textarea />
{{#if true}}
  Test
{{/if}}

And

<Textarea />
{{#if true}}
  Test
{{/if}}

is formatted to

<Textarea />

{{#if true}}
  Test
{{/if}}

Report

Prettier 2.0.5
Playground link

--parser glimmer
--print-width 40

Input:

<Textarea />
{{#if true}}
  Test
{{/if}}
  
<Textarea />

{{#if true}}
  Test
{{/if}}

Output:

<Textarea />

{{#if true}}
  Test
{{/if}}
<Textarea />
{{#if true}}
  Test
{{/if}}

Expected behavior (maybe):

<Textarea />
{{#if true}}
  Test
{{/if}}
  
<Textarea />

{{#if true}}
  Test
{{/if}}

[Alonski]

Anyone want to pair with me on trying to fix this?

[Alonski]

The really weird thing is that this only seems to happen for <Textarea>
Playground Link

[Alonski]

@fisker Would you be up to pairing with me next week to try and figure this out?

[fisker]

I believe @dcyriller is more familiar with it. Don't worry, If you have problems, everyone will help.

[Alonski]

Ok :) This is the only thing blocking me from going all in on Prettier in the main app I work on.

[Alonski]

This seems to have been caused by this PR:
#6354

[dcyriller]

The bug appears to be in glimmer.

In this AST, the TextNode chars attribute is "" instead of "/n".

[Alonski]

This PR is probably the "cause" for this issue: tildeio/simple-html-tokenizer#59
Specifically this: https://github.com/tildeio/simple-html-tokenizer/blob/5a7739761ffc4358dd46399b5a2b62da9e0d7ba6/src/evented-tokenizer.ts#L137-L139

Looking at this code I found that <Pre /> is also causing these issues.

[rwjblue]

@dcyriller - Updating to @glimmer/[email protected] should resolve this.

[dcyriller]

Awesome, thank you @rwjblue