sass/dart-sass

Add ASCII output support

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#568 opened on Jan 11, 2019

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enhancementhelp wanted

Description

I've been working on a product using libsass/sassc and have migrated it to Dart Sass. Presently, this product doesn't support UTF-8 characters in stylesheets.

It looks like Dart Sass only supports outputting as UTF-8, with dart-lang/sdk#11744 being the blocker given in the README for why there's no support for more encodings (UTF-16, etc). Dart does however appear to have an AsciiEncoder.

For the time being, we've added an extra step to CSS escape non-ASCII characters in generated stylesheets. (On a related note, we also remove the @charset 'UTF-8'; atrule, both because it would be technically incorrect for an ASCII-encoded stylesheet, and because of #567.)

This isn't trivial because of sourcemaps, so we're doing this step with a PostCSS plugin.

Would adding ASCII-encoded output support be in scope of Dart Sass? I'd imagine when Dart adds other encoders, having this ready would let other encodings be sibling output options alongside UTF-8 and ASCII.

Contributor guide

Tech stack
None
Domain
tooling
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
over 1 week
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Dart programmingCharacter encoding basicsSourcemap knowledge
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20
Research direction
Explore the Dart AsciiEncoder class and how it can be used for output encoding. Review the existing UTF 8 output implementation in the emitter source files. Understand how sourcemap generation works and how different encodings affect byte offsets. Check the linked Dart SDK issue dart lang/sdk#11744 for progress on encoder support. Discuss with maintainers about the desired scope and whether ASCII should be an option alongside UTF 8.