Would auto-formatting / auto-indentation make sense for this project?

[simonw]

I've been hoping to find a templating equivalent of Black for quite a while. Could automatic formatting fit this project?

[simonw]

Whether or not this feature makes sense, this project is excellent - thank you so much! It just found a couple of bugs in Datasette. simonw/datasette@d0c752d

[thibaudcolas]

Hey @simonw, well I’m glad you’re finding it helpful! 🙂 99% of the credit for those two issues should go to https://github.com/motet-a/jinjalint, from which most of Curlylint’s parser comes from (I’ve only changed the parser for a few bug fixes so far).

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For auto-formatting – this is something I’m personally very interested in as well, as a heavy user of both Prettier and black. I’ve been keen to work on this for a while, but need to be realistic with the time commitment something like this would take, so the short answer is "not for now", I think.

The long answer is that there is some interest in making this happen in the Prettier world, and to me it feels like a good ecosystem for this to be done within, since there is so much similarity between all the curly template languages. So far the most promising attempt there is https://github.com/trivago/prettier-plugin-twig-melody, and I’m hoping this will be something we can leverage for Jinja / Django templates.

For Curlylint, I can see a few ways for this project to help make auto-formatting happen:

• First there’s the parser. There aren’t so many parsers out there that provide a useful AST for both HTML, and template language syntax. This would obviously be a good basis for auto-formatting – assuming the parser is good you’d "just" need a printer for the AST. That parser needs work, regardless of whether it’s for linting or auto-formatting.
• Then there’s the parser’s unit tests! Currently there aren’t many. I’d really like to write a lot, in a format that would be helpful to the current parser, but that could also be used to a JS-implemented parser.
• And smoke tests. https://github.com/thibaudcolas/curlylint/tree/main/tests contains code from many projects partly for me to have an easy set of templates to test all kinds of static analysis on curly templates.

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If you or anyone else wants to help with this, I can see a few options:

• Testing Curlylint more. I’m only using it on a handful of projects currently, and have an ok understanding of the parser, but it really does need to be more battle-tested before I’d let any tool rewrite code based on it. Any feedback on that front is appreciated.
• Same as the above, but with unit tests :) That parser code really needs its 100% coverage as a minimum.
• Finally to depart from the above I’d also be interested for someone to investigate whether the existing indent rule could be re-purposed for automated indentation. It’s not something I’m too keen on myself (I’d rather work on a full-on parser!), but if it’s not that much work to make use of that existing indent logic, might as well.

[yaegassy]

I'm also interested in the jinja2, django template formatter.

It seems that there is a package called "vsot", but unfortunately it is not maintained.

PRE-APLHA, mostly unmaintained

• https://pypi.org/project/vsot/
• https://github.com/benhowes/vsot

(Something, if it would be helpful.)

Of course, if there is a dedicated plugin for prettier, I'm sure that's fine.

[panosl]

I'm also interested in the jinja2, django template formatter.

It seems that there is a package called "vsot", but unfortunately it is not maintained.

PRE-APLHA, mostly unmaintained

* https://pypi.org/project/vsot/

* https://github.com/benhowes/vsot

(Something, if it would be helpful.)

Of course, if there is a dedicated plugin for prettier, I'm sure that's fine.

Now that looks promising!

[thibaudcolas]

Ah that’s really interesting, thank you for sharing it here. There aren’t that many parsers out there for HTML + template syntax, particularly with enough information for pretty-printing, so it’s always interesting to compare options at the very least.

[yaegassy]

@thibaudcolas I recently discovered a tool called djhtml. It appears to be actively being developed now.

• GitHub
  • https://github.com/rtts/djhtml
• PYPI
  • https://pypi.org/project/djhtml/

DjHTML is an indenter and not a formatter

Currently, the feature seems to be only for indent adjustment, but we can expect more in the future.

[thibaudcolas]

@yaegassy 🤘 that seems pretty promising, thank you for sharing. I’ll have to try that out myself.