[DO NOT MERGE] Glimmer 2 Final Countdown

[chadhietala]

Update

Markdown file did not pan out. There was much confusion on what tasks were taken. So what is the plan? I have migrated all of the tasks and relevant information to a Trello board 😱 . No worries you do not need to signup for Trello or any of that nonsense. Please continue 🔒 ing things by just commenting on this PR along with the link to the trello board. Example:

Hey everyone I'm going to take https://trello.com/c/pR3KtDCH/20-ensure-falsy-values-do-not-become-class-names 🔒 .

I will then personally go move the card to "In Progress". Hopefully this is not too much burden and will actually result in clear direction of "what needs to be done".

Thanks everyone!

Board
https://trello.com/b/6C6i3eGV/glimmer-2

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This is the 🔥 🔥 🔥 burn down 🔥 🔥 🔥 issue to ship Glimmer 2. While there are still in flight PRs, this is known state of the world at SHA b418b95.

We are experimenting on using a temporary Markdown instead of a regular checklist so that we can add line comments for each item. Do not merge this pull request.

[chancancode]

• Complete all test migration described in [Pls send halp!] The Ultimate Glimmer 2 Test Porting Guide #13127

[chancancode]

• Not usable in a block: Failing test

[chadhietala]

• Implement {{action}}

[kiwiupover]

There are a few {{yield}} test missing. {{yield foo}} at least. I will work on those tonight in #13213

[mmun]

I will implement {{partial}}.

[zackthehuman]

htmlSafe is not actually supported in double-curlies from what I can tell. The PR mentioned here only fixes the tests to make it possible to compare HTMLBars and Glimmer2 behavior side-by-side. The feature is still missing (and I'm trying to implement it).

[chancancode]

You should look here: https://github.com/tildeio/glimmer/blob/master/packages/glimmer-runtime/lib/compiled/opcodes/content.ts

1. The AppendOpcode is responsible for inserting the content during "initial render" (but this also applies to things like an {{#if}} changing from true to false, thus tearing down the block and rendering a different one). It needs to be updated to handle both safe and non-safe strings.
2. The AppendOpcode emits an UpdateAppendOpcode that is responsible for keeping the curlies up-to-date when the content changes. It needs to remember which "mode" it was in previously and do the right thing. (Handling safe <-> non-safe strings, etc).
3. You can look at how the "Trusting" versions of opcodes, which are for triple-curlies. You can probably refactor things to share more code.
4. Keep in mind the "const reference optimization" as you do this: Implement ConstReference optimization glimmerjs/glimmer-vm#109
5. Future work: we also need to support appending DOM nodes into the curlies (helpers etc can return DOM nodes to be inserted). But we can tackle that separately.
6. Ideally, we would like to minimize the "mode switching" stuff by emitting specialized opcodes, but I couldn't think of any cases where we can know these information ahead of time (other than the const case, which simply does not emit updating opcodes).

[zackthehuman]

I'm investigating htmlSafe.

[asakusuma]

I'm going to take a stab at this

EDIT: #13337

[chadhietala]

Bump. Just want to notify everyone in this thread on the way we are going to track things going forward. Please read the initial comment for an update.

[zackthehuman]

I'm working on: https://trello.com/c/VBKxChRO/34-class-helper-not-usable-in-a-block

[chadhietala]

Closing in favor of #13644