Syntax error on valid characters in anchor names

[Freso]

yamllint complains about the use of periods (.) in anchor names. As far as I can discern, ns-anchor-char allows all ns-chars except for c-flow-indicators (,[]{}).

Periods (.) are x2E which is well within the range of [x20-x7E] given in c-printable and is not one of the chars excluded from ns-char via b-char, c-byte-order-mark, or s-white.

I don’t see any way to configure yamllint to not balk on this, or at least reduce this to a warning (other than comment-disabling). I can definitely see limiting anchor names to alphanumeric characters to be desired for many use cases (for compatibility/interoperability), but the spec allows for a wider range of characters used here, so this should probably reasonably be a configuration toggle.

%YAML 1.2
---
test:
  - &test-with-.period "This is a test of an anchor with a period (`.`)."
test2:
  - *test-with-.period
...

> yamllint --version
yamllint 1.35.1
> yamllint test.yaml
test.yaml
  4:16      error    syntax error: expected alphabetic or numeric character, but found '.' (syntax)

[perlpunk]

I just want to comment that the underlying issue is in pyyaml.
It is more restrictive than the YAML spec regarding what is allowed in anchor names.
yaml/pyyaml#373
yaml/pyyaml#389
The current pyyaml maintainer wants to keep it that way. The same is true for libyaml, btw.

Not sure if yamllint can work around that syntax error from pyyaml.