@jesscss/plugin-less

@jesscss/plugin-less

The Less language engine for Jess — the Less parser wired in with Less v5 rendering defaults.

This is the one shipping surface today. Jess is Less.js v5, and plugin-less is where that lives: it layers the Less grammar (@jesscss/less-parser) onto the Jess compiler, registers the Less built-in functions (@jesscss/fns), and sets the v5 output defaults. The jess and lessc CLIs load it by default, so if you render .less you are already using it — you don't need to install this package separately for normal CLI use.

What it does

• Parses .less into the Jess AST and hands it to the engine for a single evaluate-and-emit pass.
• Registers the Less/Sass style-function library so lighten(), percentage(), string and list helpers, etc. are available during evaluation.
• Owns the Less v5 output defaults — the single source of truth the lessc CLI imports so CLI and engine defaults can never drift.

Less v5 output defaults

The defaults this plugin applies:

• collapseNesting: false — nesting is preserved by default. Less 4.x flattened selectors; in v5 that flattening is an explicit opt-in (--collapse-nesting on the CLI).
• mathMode: 'parens-division', unitMode: 'preserve', equalityMode: 'less', leakyScope: true, bubbleRootAtRules: true.

These keep the Less 4.x command surface (flags, stdin/stdout, exit codes) while producing Less v5 output semantics.

Status

Alpha. This is the "Now" / Less.js tier — the earned, shipping-today surface. It is real and renders real Less, but it is early software with known rendering gaps and expected failures; don't ship it to production yet, and please report bugs.

The programmatic plugin/compiler API is not yet stabilized — the jess / lessc CLIs are the public surface for the alpha. Watch the docs site for the API once it settles.

• Project overview & positioning: https://github.com/jesscss/jess#readme
• Docs: https://jesscss.github.io/ (currently pre-alpha content)
• Issues: https://github.com/jesscss/jess/issues
• License: MIT