Hello!

There seems to be a bug with validateAttributeSeparator when attributes are named in a specific way. If one attribute is named e.g. a, there cannot be an attribute named after a-b it, but it works the other way round (a-b before a).

For example, given the lint rule:

{
  "validateAttributeSeparator": {
    "separator": " ",
    "multiLineSeparator": "\n  "
  }
}

...and the following pug code:

div(a a-b="foo")

...the linter fails with Invalid attribute separator found, pointing at the dash in a-b. Interestingly, with the same lint rule, the following pug code with an attribute named a-a:

div(a a-a="foo")

...fails with error:

TypeError: Cannot read property 'line' of undefined
      at lib/rules/validate-attribute-separator.js:9:4527
      at lib/pug-file.js:9:18727
      at Array.forEach (<anonymous>)
      at PugFile.iterateTokensByFilter (lib/pug-file.js:9:18624)
      at PugFile.iterateTokensByType (lib/pug-file.js:9:18937)
      at module.exports.lint (lib/rules/validate-attribute-separator.js:9:2008)
      at lib/linter.js:9:8270
      at Array.forEach (<anonymous>)
      at Linter._checkFile (lib/linter.js:9:8092)
      at Linter.checkString (lib/linter.js:9:3918)
      at Linter.checkFile (lib/linter.js:9:2741)
      ...

When the attributes are re-ordered, the pug code is linted without errors:

div(a-b="foo" a)
div(a-a="foo" a)

The same bug occurs in multiline attributes.

pug-lint version used: 2.5.0