Evaluator

Evaluator.js handles variable substitution and colour function dispatch during theme compilation.

Theme Reference

setTheme(theme) gives the Evaluator a back-reference to the owning Theme instance. This enables source-location lookups: when an evaluation error occurs, the Evaluator calls theme.findSourceLocation(dottedPath) and, if a location is found, appends file:line:col to the error’s trace context. The result is error messages that point directly to the offending line in the original YAML source.

Regex Patterns

Three static patterns drive token detection:

• Evaluator.sub — matches variable references in three syntaxes: $(var), $var, ${var}
• Evaluator.func — matches function calls: functionName(args)
• Evaluator.paletteAlias — matches palette alias syntax: $$name, $($name), ${$name}. These are expanded to $palette.name, $(palette.name), ${palette.name} before resolution begins.

evaluate(decomposed)

The main entry point. Takes an array of {flatPath, value} entries and resolves them in-place.

Before the resolution loop begins, a pre-pass expands all palette aliases ($$name → $palette.name) via expandPaletteAliases(). This ensures palette references are in their canonical form before any resolution attempts.

Resolution is then iterative:

1. Loop through all entries, calling #evaluateValue() on each string value.
2. #evaluateValue() dispatches based on the value’s form:
   • Hex literal → #resolveHex (pass through)
   • Variable reference ($(...)) → #resolveVariable (look up in pool)
   • Function call (func(...)) → #resolveFunction (dispatch to colour function)
   • Otherwise → #resolveLiteral
3. Repeat passes until no unresolved tokens remain or maxIterations (10) is reached.
4. If max iterations are exhausted, a Sass error is thrown listing the unresolved tokens. This catches circular references.

All errors thrown during evaluation are enriched with source locations when available — the Evaluator uses its Theme reference to resolve the dotted path back to a file:line:col position in the original YAML.

Function Dispatch

#resolveFunction parses the function call and delegates to #colourFunction, which switches on the function name:

Function	Description
lighten	Lighten a colour by a percentage
darken	Darken a colour by a percentage
fade	Reduce alpha (increase transparency)
solidify	Increase alpha (reduce transparency)
alpha	Set alpha to a specific value
invert	Invert a colour
mix	Mix two colours with a ratio
css	Output as CSS colour string

The default case passes the raw expression to Colour.toHex() as a Culori passthrough — any valid Culori colour expression works.

This switch statement is the extension point for adding new colour functions.

ThemePool Integration

Each resolution creates or updates ThemeToken entries in the pool:

• New tokens are created with raw value, resolved value, and kind.
• Existing tokens have their value updated and resolution trail appended.
• The pool’s lookup map enables chained dependency resolution — later tokens can reference earlier-resolved values.
• Resolution trails are tracked for the resolve command’s debugging output.