@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 Less language engine behind the shipping alpha surface. plugin-less layers the Less grammar (@jesscss/less-parser) onto the Jess compiler, registers the Less built-in functions (@jesscss/fns), and sets the current output defaults. The jess CLI loads 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 current Less-facing output defaults used across the alpha surface.

Current 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', leakyScope: true, bubbleRootAtRules: true.

These keep the current Less-facing surface aligned on one set of output semantics.

Equality is not among them, because it is not a mode. The Less grammar lowers = to the loose comparison primitive, and that lowered node is what the evaluator reads — there is no equalityMode for this plugin to set. See docs/design/RESOLVED-SEMANTICS-AND-NAMING.md §5.1 and §7.3 for the full op table, and §5.2 for the one .less behaviour this shifts: a quoted operand now compares on string ground, so a = "a" is true where Less 4.x answers false.

Status

Alpha. This is the shipping Less-facing engine in the current Jess alpha. It 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 CLI is the documented 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