v0.5.1

Added

• The empty language range :lang("") now has its Selectors 4 meaning — "the
  element's language is not known" — where it was rejected as a malformed
  range. It is the complement of :lang(*), so it translates to that range's
  test negated: e:lang("") is
  e[not(ancestor-or-self::*[@lang][1][string-length(@lang) > 0])] under
  Mode::Html, and the same shape over @xml:lang under Mode::Generic and
  over both attributes under Mode::Xhtml. An empty attribute counts as no
  language, as it does for :lang(*): an element under lang="" matches
  :lang("") rather than inheriting the tag above it. XPath's own lang()
  cannot express this, so Mode::Generic walks the language attribute
  directly, as it already did for :lang(*).

Changed

• A :lang() language range that no language tag could match — an empty
  subtag (en-, --x) or a * glued to one rather than standing as a whole
  subtag (en*, *en) — is now refused by the translator, which names it:
  the :lang() language range "en-" (an empty subtag, which a language range cannot have). These were rejected by the argument grammar before, as
  `lang` is not a supported pseudo-class or pseudo-element — a message
  that named neither the range nor what was wrong with it. So they are now
  Error::Unsupported (with no offset) where they were Error::Parse (with a
  caret on lang); the set of selectors that error is unchanged apart from
  :lang(""), which now translates. The grammar still decides what it alone
  can: whether the tokens assemble into ranges at all, which is where
  :lang(), :lang(5), :lang(en fr) and a stray comma are still refused.
• Every message payload echoed from the selector is bounded by one rule: a
  :lang() range is now sanitized and elided past 40 bytes, as a token or
  pseudo-class name in a parse error already was. This is visible only in the
  :lang() errors above and in the existing "a wildcard outside the final
  subtag" one, whose range came through raw however long it was.

Fixed

• A :lang() range built from more than one token is no longer refused when
  it follows another range in the list: :lang(en, *-CH) and
  :lang(en, de-*) now parse, as :lang(*-CH, en) and :lang(de-*, en)
  already did. The argument grammar reads whitespace as a range terminator,
  and the flag recording it was not cleared once the next range had started,
  so the space after a comma went on separating the tokens of every range
  after it — making the multi-token ranges (*-CH, which the tokenizer
  splits into * and -CH) look like two ranges with no comma between them.
  Whitespace inside a range is still an error: :lang(en, * -CH) and
  :lang(en fr) are refused as before.