function compileMode()

in src/site/assets/highlight.js-11.2.0/highlight.js [1393:1463]
50 lines of code
19 McCabe index (conditional complexity)

      function compileMode(mode, parent) {
        const cmode = /** @type CompiledMode */ (mode);
        if (mode.isCompiled) return cmode;

        [
          scopeClassName,
          // do this early so compiler extensions generally don't have to worry about
          // the distinction between match/begin
          compileMatch,
          MultiClass,
          beforeMatchExt
        ].forEach(ext => ext(mode, parent));

        language.compilerExtensions.forEach(ext => ext(mode, parent));

        // __beforeBegin is considered private API, internal use only
        mode.__beforeBegin = null;

        [
          beginKeywords,
          // do this later so compiler extensions that come earlier have access to the
          // raw array if they wanted to perhaps manipulate it, etc.
          compileIllegal,
          // default to 1 relevance if not specified
          compileRelevance
        ].forEach(ext => ext(mode, parent));

        mode.isCompiled = true;

        let keywordPattern = null;
        if (typeof mode.keywords === "object" && mode.keywords.$pattern) {
          // we need a copy because keywords might be compiled multiple times
          // so we can't go deleting $pattern from the original on the first
          // pass
          mode.keywords = Object.assign({}, mode.keywords);
          keywordPattern = mode.keywords.$pattern;
          delete mode.keywords.$pattern;
        }
        keywordPattern = keywordPattern || /\w+/;

        if (mode.keywords) {
          mode.keywords = compileKeywords(mode.keywords, language.case_insensitive);
        }

        cmode.keywordPatternRe = langRe(keywordPattern, true);

        if (parent) {
          if (!mode.begin) mode.begin = /\B|\b/;
          cmode.beginRe = langRe(mode.begin);
          if (!mode.end && !mode.endsWithParent) mode.end = /\B|\b/;
          if (mode.end) cmode.endRe = langRe(mode.end);
          cmode.terminatorEnd = source(mode.end) || '';
          if (mode.endsWithParent && parent.terminatorEnd) {
            cmode.terminatorEnd += (mode.end ? '|' : '') + parent.terminatorEnd;
          }
        }
        if (mode.illegal) cmode.illegalRe = langRe(/** @type {RegExp | string} */ (mode.illegal));
        if (!mode.contains) mode.contains = [];

        mode.contains = [].concat(...mode.contains.map(function(c) {
          return expandOrCloneMode(c === 'self' ? mode : c);
        }));
        mode.contains.forEach(function(c) { compileMode(/** @type Mode */ (c), cmode); });

        if (mode.starts) {
          compileMode(mode.starts, parent);
        }

        cmode.matcher = buildModeRegex(cmode);
        return cmode;
      }