fix: correctly handle even numbers of backslashes before closing string quote

[chatman-media]

Problem

The skipString function in src/function-tokenizer.ts used a one-character look-behind to decide whether a closing quote is escaped:

const prev = source.charAt(pos - 1)
if (ch === quote && prev !== '\\') {
  pos++
  return
}

This check is incorrect when an even number of backslashes precedes the closing quote. For example, the source string 'test\\' represents the JS value test\ (a string ending with one literal backslash). Here the source characters are ' t e s t \ \ '. Because the character immediately before the closing ' is a backslash, the old code treats the quote as escaped and runs past the end of the string, ultimately throwing:

SyntaxError: Parsing parameter list, did not expect EOF token

This manifests in practice whenever a class constructor has a parameter with a string default value whose final character is a backslash (e.g. Windows filesystem paths):

class MyService {
  constructor(dep1, basePath = 'C:\\Windows\\', dep2) {}
}

Fix

Count all consecutive backslashes before the quote. An even count means each pair cancels out (literal backslash characters), so the quote is the end of the string. An odd count means the last backslash is an escape for the quote, so the string continues.

if (ch === quote) {
  let backslashCount = 0
  let i = pos - 1
  while (i >= 0 && source.charAt(i) === '\\') {
    backslashCount++
    i--
  }
  if (backslashCount % 2 === 0) {
    pos++
    return
  }
}

Tests

• Added a new tokenizer test (can skip strings ending with an even number of backslashes) covering 2-backslash and 4-backslash cases.
• Added a new param-parser bug regression test (string default ending with even backslashes) that directly exercises the real-world failure scenario, including a check that single-backslash escaped quotes still work correctly.

All 235 tests pass.

[jeffijoe]

Please remove the new comments from the test files

[chatman-media]

Done — removed the comments from both test files in 769ea9d.

[jeffijoe]

Wouldn't checking the immediate next character (and consuming it) if it's also a backslash work as well?

[chatman-media]

Yes, that's cleaner — switched to exactly that in 769ea9d: when a backslash is encountered, both it and the following character are consumed (pos += 2), so an escaped quote never terminates the scan and a literal backslash can't swallow the closing quote. Behavior is identical (all snapshots unchanged, 235 tests pass).

[jeffijoe]

@chatman-media I'll need you to rebase this to latest master before I can merge it. Thanks!

[chatman-media]

Done — rebased onto the latest master (now a clean 3-commit history on top of 8b45b70, no merge commit). The diff is just the tokenizer fix + tests/snapshot. npm ci and the tokenizer/param-parser suites pass locally. Ready when you are — thanks!

[coveralls]

coverage: 100.0%. remained the same — chatman-media:fix/skipstring-even-backslashes into jeffijoe:master

[jeffijoe]

Released as v13.0.5, thanks!