strip-comments.js

import error from "./error.js";

function unexpectedToken(type, occasion, filename, line) {
  var msg = "`" + type + "` encountered when " + occasion;
  throw error("UNEXPECTED_TOKEN", msg, { filename: filename, line: line });
}

export default function stripComments(input, options) {
  options = options || {};

  // Default: strip unbuffered comments and leave buffered ones alone
  var stripUnbuffered = options.stripUnbuffered !== false;
  var stripBuffered = options.stripBuffered === true;
  var filename = options.filename;

  var out = [];
  // If we have encountered a comment token and are not sure if we have gotten
  // out of the comment or not
  var inComment = false;
  // If we are sure that we are in a block comment and all tokens except
  // `end-pipeless-text` should be ignored
  var inPipelessText = false;

  return input.filter(function (tok) {
    switch (tok.type) {
      case "comment":
        if (inComment) {
          unexpectedToken(
            "comment",
            "already in a comment",
            filename,
            tok.line,
          );
        } else {
          inComment = tok.buffer ? stripBuffered : stripUnbuffered;
          return !inComment;
        }
      case "start-pipeless-text":
        if (!inComment) return true;
        if (inPipelessText) {
          unexpectedToken(
            "start-pipeless-text",
            "already in pipeless text mode",
            filename,
            tok.line,
          );
        }
        inPipelessText = true;
        return false;
      case "end-pipeless-text":
        if (!inComment) return true;
        if (!inPipelessText) {
          unexpectedToken(
            "end-pipeless-text",
            "not in pipeless text mode",
            filename,
            tok.line,
          );
        }
        inPipelessText = false;
        inComment = false;
        return false;
      // There might be a `text` right after `comment` but before
      // `start-pipeless-text`. Treat it accordingly.
      case "text":
        return !inComment;
      default:
        if (inPipelessText) return false;
        inComment = false;
        return true;
    }
  });
}