Function enter

packages/css-data/src/parse-css.ts:136–185

(node)

  csstree.walk(ast, {
    visit: "Function",
    enter(node) {
      const fnNode = node as csstree.FunctionNode;
      if (fnNode.name !== "var" || !fnNode.loc) {
        return;
      }
      const varRef = parseCssVar(fnNode);
      if (!varRef) {
        return walkSkip;
      }

      const direct =
        customProperties.get(`--${varRef.value}`) ??
        cssVars?.get(`--${varRef.value}`);

      if (direct !== undefined) {
        if (!customProperties.has(`--${varRef.value}`)) {
          usedCssVarsSubstitution = true;
        }
        subs.push({
          start: fnNode.loc.start.offset,
          end: fnNode.loc.end.offset,
          text: direct,
        });
        return walkSkip;
      }

      // Try inline fallback — may itself contain var() references.
      if (varRef.fallback?.type === "unparsed") {
        const fbValue = varRef.fallback.value;
        // If the fallback itself has no var(), use it directly.
        // Otherwise recursively resolve any nested vars inside it.
        const fallbackResult = fbValue.includes("var(")
          ? resolveVars(fbValue, customProperties, cssVars, depth + 1)
          : { resolved: fbValue, dropped: [] };
        if (
          fallbackResult !== undefined &&
          fallbackResult.dropped.length === 0
        ) {
          subs.push({
            start: fnNode.loc.start.offset,
            end: fnNode.loc.end.offset,
            text: fallbackResult.resolved,
          });
          return walkSkip;
        }
      }

      dropped.push(`--${varRef.value}`);
      return walkSkip;
    },
  });

  let resolved = value;