esformatter-quotes/index.js

esformatter plugin: enforces coding style that string literals are delimited with single or double quotes.

//jshint node:true, eqnull:true
'use strict';

var DOUBLE_QUOTE = '"';
var SINGLE_QUOTE = '\'';

var avoidEscape;
var disabled;
var quoteValue;
var alternateQuote;

// Helper to generate a string that repeats itself n times
//   e.g. ("ab", 2) -> "abab"
function repeat(str, n) {
  return new Array(n + 1).join(str);
}

exports.setOptions = function(opts) {
  opts = opts && opts.quotes;
  if (!opts || (opts.type == null && opts.avoidEscape == null)) {
    disabled = true;
    return;
  }
  disabled = false;
  if (opts.type != null) {
    quoteValue = opts.type === 'single' ? SINGLE_QUOTE : DOUBLE_QUOTE;
    alternateQuote = opts.type !== 'single' ? SINGLE_QUOTE : DOUBLE_QUOTE;
  }
  avoidEscape = opts.avoidEscape;
};


exports.tokenAfter = function(token) {
  if (disabled) return;

  if (token.type === 'String') {
    var content = token.value.substr(1, token.value.length - 2);
    var quote = quoteValue;
    var alternate = alternateQuote;

    var shouldAvoidEscape = avoidEscape &&
      content.indexOf(quote) >= 0 &&
      content.indexOf(alternate) < 0;

    if (shouldAvoidEscape) {
      alternate = quoteValue;
      quote = alternateQuote;
    }

    // we always normalize the behavior to remove unnecessary escapes
    // If the escaped quote should be unescaped, then escape it (e.g. '\"' -> '"')
    //   However, don't remove escapes from slashes (e.g. '\\"' -> '\\"')
    // DEV: RegExp explained:
    //   - We want to start on a non-slash character to only match at boundaries
    //      (i.e. `^|\`, the 4 slashes are 1 slash in RegExp)
    //   - We want to prevent replacing escaped slashes (i.e. `\\` should not be replaced, this is 8 slashes in RegExp)
    //   - We want to replace `\"` with `"` as the slash is unnecessary
    ///  - We match as many pairs as possible for `\"` due to requiring a leading word boundary on our next match (which won't exist)
    var alternateEscape = new RegExp('(^|[^\\\\])((?:\\\\{2})*)((?:\\\\' + alternate + ')+)', 'g');
    content = content.replace(alternateEscape, function replaceQuotes (input, boundaryChar, leadingEscapedSlashes, escapedQuoteChars, match) {
      // DEV: We divide the escapedQuoteChars by 2 since there are 2 characters in each escaped part ('\\"'.length === 2)
      return boundaryChar + leadingEscapedSlashes + repeat(alternate, escapedQuoteChars.length / 2);
    });

    // If the first character is a quote, escape it (e.g. "'hello" -> '\'hello')
    //   or if a character is an unescaped quote, escape it (e.g. "hello'" -> 'hello\'')
    // If we are an unescaped set of quotes, escape them (e.g. "hello'" -> 'hello\'', "hello''" -> 'hello\'\'')
    // DEV: JavaScript starts the next match at the end of the current one, causing us to need a function or loop.
    var quoteEscape = new RegExp('(^|[^\\\\])((?:\\\\{2})*)(' + quote + '+)', 'g');
    content = content.replace(quoteEscape, function replaceQuotes (input, boundaryChar, leadingEscapedSlashes, quoteChars, match) {
      return boundaryChar + leadingEscapedSlashes + repeat('\\' + quote, quoteChars.length);
    });
    token.value = quote + content + quote;
  }
};