hbs-loader incompatible with components named `Link`

[runspired]

Example error:

ERROR in ../../engines/labor-employee-engine/components/shift-day.hbs
Module Error (from ../../../../../../../../../../../Users/runspired/github/private/fnb/node_modules/@embroider/hbs-loader/src/index.js):
(Emitted value instead of an instance of Error) SyntaxError: Closing tag </div> did not match last open tag <Link> (on line 24): 

The issue here I think is that something the loader is using is confusing <Link></Link> for the element <link />. Capitalization needs to be taken into account.

[NullVoxPopuli]

I have this same problem in my work's codebase, and is one reason why embroider migration has been paused in favor of v2 addon migration :upside_down_face:

[ef4]

I can't reproduce this. Please try to make a shareable reproduction.

I suspect some addon is installing an AST transform that misbehaves under embroider.

[NullVoxPopuli]

@runspired do you have ember-css-modules installed? Guess it's time to start comparing our deps :sweat_smile:

[runspired]

@NullVoxPopuli I do not, but the addon that is causing this is an engine 🤔

[runspired]

@ef4 I think your intuition is half-right. It only reproduces if I include any template preprocessor, even one that does literally nothing. Here's a repro of that: https://github.com/runspired/link-error-demo

[runspired]

I spent a little time tinkering with different component names, this problem specifically occurs when a template preprocessor is present and the lower-case of a component name collides with an always-self-closing html element (link for example). So a component named Input or Script or A is fine, but one named Hr or Br or in this case Link is not.

[ef4]

Thanks. Your reproduction let me narrow it down to a bug in the glimmer AST printer. See https://github.com/glimmerjs/glimmer-vm/pull/1388

That PR is just a failing test case. If somebody wants to have a go, the failing test makes it pretty clear if you've succeeded.

[ef4]

This matters for Embroider because we rewrite all v1-formatted addons to v2-format (so that subsequent build stages can be in a pure v2 world and be much simpler). One thing we do during that rewriting is run any custom transforms. That means that templates get parsed and re-printed. So a bugs in the printer effect us in a way that doesn't matter in classic builds.

This bug only happens in v1 addons. In app code, it shouldn't occur. And in v2 addons it shouldn't occur. It's only the compat layer for v1 addons that relies on the glimmer AST printer.

[ef4]

I think this bug might apply to all these names:

• area
• base
• br
• col
• command
• embed
• hr
• img
• input
• keygen
• link
• meta
• param
• source
• track
• wbr

https://github.com/glimmerjs/glimmer-vm/blob/07db0655c8d4b5c71792bf49ba3b547c196e460a/packages/%40glimmer/syntax/lib/generation/printer.ts#L9

based off investigation by @Windvis.