Maintain relative order of attributes and comments within an ElementNode

[charlespierce]

Info

Currently, if you have a comment in among the attributes of an angle bracket component, the Printer will output that comment at the end of the list (even if it was originally in a different location). This causes problems if you have a bare attribute (without a value), as the resulting template is now invalid:

<Foo {{!-- This is a comment --}} attribute></Foo>

Becomes

<Foo attribute {{!-- This is a comment --}}></Foo>

Which then fails to parse with the error:

Using a Handlebars comment when in the `afterAttributeName` state is not supported

Changes

• Updated the printer to order all of the attributes, modifiers, and comments of an element by their original position in the source, preserving the user's ordering when printing the AST.
• Updated the parser to not error when a Handlebars comment follows a valueless attribute.

Tested

• Added test to confirm that the ElementNode ordering is preserved.
• Added test to confirm that a comment is valid after a valueless attribute.
• All tests pass.

[rwjblue]

There are two major issues here:

1. when we print out the AST we end up discarding the original ordering of attributes, modifiers, and comments
2. the error mentioned should be removed, and tests added to ensure that it works properly

[rwjblue]

Can you re-export this from the top level @glimmer/syntax index file? That will ultimately allow me to remove the original code this is copied from (over in ember-template-recast).

[charlespierce]

Done! Worth noting, the detection of whether a Node is invisible or not is slightly different from the original in ember-template-recast, not sure if that will impact your ability to re-use it there.

[rwjblue]

Ya, it definitely will but ember-template-recast has not yet updated to the latest @glimmer/syntax yet. When it does, it'll need to deal with this new loc format as well, so it should be good to go.

[dcyriller]

FYI ember-template-lint/ember-template-recast@f9de578

EDIT: ember-template-lint/ember-template-recast#662 would be a possible implementation