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Rework oxc_prettier
#5068
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@leaysgur is writing a series of articles in preparation of this task: I'm also working on comment attachments to unblock prettier. |
Does this mean that you aim to implement Prettier equivalent which achieves with 60+ utils? 🫨 FYI: Babel also has relevant code(just 300 loc), but that did not seem to meet Prettier's requirement. |
We need to figure out what exactly is prettier doing with those 60+ utils 🥲 |
For those who are interested in algorithms under the hood, prettier is based on https://homepages.inf.ed.ac.uk/wadler/papers/prettier/prettier.pdf, |
It has been 3 weeks since I started reading the Prettier source code.
There are 3 ways:
It is written in Japanese, but it is all code, so you can understand it. 😉 I also recommend to run
I will post some topics for discussion in a few days. |
As you may know, Prettier's formatting process consists of roughly 3 phases:
Comments are collected in P1 and used in P2. In P1:
As a result, some AST nodes have In P2 (I haven’t read the code in detail here yet),
In OXC, part of the necessary information is already implemented and can be obtained. / #5785 However, just like with Babel, that information may be different from what Prettier requires... So, I think I’ve generally understood "what" Prettier is doing. However, as for "why" Prettier does it that way, I can only say it’s because that’s Prettier’s opinion. Incidentally, there seem to be at least around 120 issues related to JS/TS at the moment, but about 50 of them are related to comments, with some remaining unresolved since as far back as 2017. |
So, what I would like to discuss(confirm?) is: where should If the goal is to achieve compatibility, I think it would mean porting almost all of Prettier’s lines.
I believe the original aim of this issue was this, but again, is this an acceptable? If we decide to proceed, let’s consider how we might specifically approach it... Fortunately, the 3 phases have isolated inputs and outputs, so:
I think reducing the gaps between each phase will be important. For that, we’ll need some way to directly compare the result of
// OXC
let oxcASTWithComments = oxc_prettier::parse(text);
let oxcEstreeASTWithComments = estreeJSON(oxcASTWithComments);
// let oxcBabelASTWithComments = babelJSON(oxcASTWithComments);
// Prettier
let prettierEstreeASTWithComments = Prettier.parse(text, { parser: "meriyah" });
// let prettierBabelASTWithComments = Prettier.parse(text, { parser: "babel" });
// Diff!
assert(oxcEstreeASTWithComments, prettierEstreeASTWithComments); What if we don’t aim for full compatibility?
But in that case, maybe it would be more like Anyway, this is what I was thinking these days. What do you think? |
For the long run, I envision a more configurable and less opinionated formatter. Under this assumption, we can relax the "100% compatibility" constraint. My intention is to reach a high compatibility with prettier so we can bootstrap ourself, and then start deviating behavior. I've also looked at the prettier and rustfmt issues before, comment positioning is a really difficult subject due to the natural of matching the original intent of the comment. To move things forward, I suggest @leaysgur to start refactoring our prettier code in preparation for what to come, I believe you know more about prettier than I do. You may ask @Sysix for help given they have started working on this area as well. Our code for P2 and P3 is also incomplete, I suggest to do a little bit of rework first, as well as adding more debug utilities. |
I don't think we need to do this. This will leave us too coupled with the prettier implementation, and it may end up being a waste of effort. We are already matching half of the generated text, a few more iterations of refactoring and implementing details should close our gap to prettier. |
I see, what I likely concerned about was: what exactly is meant by "high compatibility". 😅 So, It's good to know that we're not necessarily aiming for 100% compatibility. It's still uncertain how much the percentage will drop if we give up on porting completeness for comment handling, but for now, I'll move forward. Following your suggestion:
I’ll work on these whenever I have time! 🚀
I love this idea! |
Does this mean that oxc_prettier will provide a wide range of configurable options, and offer a preset called |
(Follow up of #5068 (comment)) As I posted above, comments are collected and attached to AST nodes in P1. Most comments are printed with their attached nodes like: [leadingCommentsDoc, nodeDoc]
// or
[nodeDoc, trailingCommentsDoc] But the rest of the comments are handled as needed.
There are about 40 files for printing ESTree AST to Doc.
And 15 files of them print comments on demand.
|
@leaysgur I was just informed that So instead of using our current unfinished IR and printer, we can replace them with I pinged you on discord, for full context. |
Thanks for the pinning!
Yes, and I just started reading through I hadn’t considered it as a viable option for OXC (though I’m not entirely sure why), but if we shift our goal to generating I’ll look into this soon (after finishing the regex parser rework), including:
|
I think it's the same thing as |
Hey all, just dropping by!
I feel adding support for comments to the current implementation should be feasible. Since the oxc_ast's I could do a PoC on my fork and have it up in some time. I don't know how much more work the parenthesis bit will take, but my hunch is that emitting biome IR might be more work than supporting comments in oxc_prettier's current form. Of course, people who've worked on this will know better. Curious to know what you think! |
I want to share my overall idea from end user perspective: After oxc_prettier will be created I suggest to create something like Currently my lint CI time is 50% time for prettier eslint (too much). |
you might want to consider running prettier (or oxc_prettier later) separately: |
Recently, I've been reading and researching the code related to Biome's Formatter.
|
Progress: An experiment to see if we can use just the Based on
My personal impression is that it doesn't seem impossible, but I'm not yet sure if it's the right path. 😅 Here's what I've found out:
and,
I mentioned "minimal" at the beginning because this Gist does not use the
Next, I will check this part. I don't know whether it's possible or not in the first place, though. 🙄 |
@leaysgur Thank you so much for the research. I think it's enough evidence to just implement our own thing (with some parts ported from Biome)? |
Yes..., I also think that's probably the case. And if we choose to go our own way, even if there are parts we can refer to, I feel there won't be any parts where we can borrow as code. 😓 Go back to the square one, I will re-start by understanding/refactoring the current code, and then think about what to do next. |
@leaysgur will lead this project, and is free to make any changes to the |
Thanks~! Progress is likely to be slow due to limited resources, but I will try to update progress every 2-3 days or so at the latest comment on this issue. |
List of Prettier's print implementations and exports:
I don't think we need a 1:1 counterpart for these, but aligning them makes it easier to track our progress. Next, I'll check our current implementation. Fully or partially implemented? not yet covered? etc... |
You can assume all are partially implemented 😅 Cross referencing the function in our code to the prettier counter part would definitely make things easier to follow. |
JS / AST Entry points👀:
JS / Printer APIs👀: File and fn exits / 🚧: W.I.P. / ✨: Completed
JSX, TSTBD, later... 🥲 I will investigate again and update Before that, I'm going to add some refactoring for IR creation and macros... 🚧 |
crates/oxc_prettier
was my attempt at the prettier bounty.I thought I could finish it in time, except the fact that I rushed too quickly without looking at all the requirements ... It was too late when I got blocked by printing comments.
In order to rework
oxc_prettier
, we need to understand at least:Doc
IR https://github.com/prettier/prettier/blob/main/commands.md https://github.com/oxc-project/oxc/blob/main/crates/oxc_prettier/src/doc.rsAs for the infrastructure, we already have most of the code:
Feel free to remove everything and start from scratch, and copy over the format code https://github.com/oxc-project/oxc/tree/main/crates/oxc_prettier/src/format
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