Basic public suffix list support.

[rthalley]

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 84.78261% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 93.88%. Comparing base (bfd0919) to head (87765ce). Report is 5 commits behind head on main.

Files	Patch %	Lines
dns/psl.py	84.78%	9 Missing and 5 partials :warning:

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Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1082      +/-   ##
==========================================
- Coverage   93.92%   93.88%   -0.05%     
==========================================
  Files         143      144       +1     
  Lines       13435    13527      +92     
  Branches     2606     2627      +21     
==========================================
+ Hits        12619    12700      +81     
- Misses        480      488       +8     
- Partials      336      339       +3     

Flag	Coverage Δ
unittests	93.84% <84.78%> (-0.05%)	:arrow_down:

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[pspacek]

Hello! Out of curiosity, why this needs to be in dnspython?

I mean, there are at least two existing libraries for Python:

• https://pypi.org/project/publicsuffix2/
• https://pypi.org/project/publicsuffixlist/

I wonder if there is a way improve dnspython interoperability with these? Or what is even the problem?

[rthalley]

I don't know that it "needs" to be in dnspython, but it goes along well with other things dnspython provides. Of the examples you cite, one hasn't been updated since 2019, and both of them use split(".") to convert a name into labels. This branch is based on code I've used for several years, and operates on dns.name.Name objects.

[pspacek]

I agree that split(".") is not how things should be done, definitely not. I'm just trying to find out if there is a good way to improve things for everyone and not just dnspython users, that's all.

[peterthomassen]

I did a DNS-based implementation of the PSL as a Python module (https://github.com/sse-secure-systems/psl-dns). Docs and demo are at https://publicsuffix.zone/.

This is publicly queryable, i.e. doesn't require applications to bring the PSL along. Not sure if it aligns with what you have in mind for dnspython's PSL support, but using it might avoid duplicate work and in particular update problems.

[rthalley]

I think your solution is probably better if you don't have to make too many queries and don't mind the information leak, as it would not have up-to-date problems. I had automatic updating in an earlier draft, but I got rid of it. For my typical PSL use cases, I would probably be making a rude number of queries and/or not want the information leak, so I think there's still value in this code too.

[pspacek]

Wondering out loud: Maybe best course of action - for the overall ecosystem - would be to add label-aware API to an existing library? I agree that split('.') is horrendous thing to do, but if that's the only problem maybe it can be fixed in the library instead of reinventing it here?

[rthalley]

I'll just set this one aside for now.