Easier way to check if a domain includes a valid TLD

[axelson]

I have the given requirement, given an arbitrary string, check if any valid domains are listed in the string and highlight/linkify them. I already have a basic regex to split the string into potential domains.

I would like there to be a function in PublicSuffix that could more readily answer this. Right now I am using:

  @doc """
  Check if the given host contains a valid TLD that does not comprise the entire
  host (since we don't want to create a link to a TLD)
  """
  def valid_tld?(%URI{host: nil}), do: false
  def valid_tld?(%URI{host: host}) do
    rule = PublicSuffix.prevailing_rule(host)
    rule != "*" && rule != host
  end

Which I guess seems simple enough but it might be nice to have some sort of helper.

[axelson]

Would a PR for this functionality be welcomed?

[bkirz]

Before we add new functionality to this library, would registrable_domain be closer to what you want?

def valid_tld?(%URI{host: nil}), do: false
def valid_tld?(%URI{host: host}) do
  PublicSuffix.registrable_domain(host) != nil
end

[axelson]

registrable_domain/2 doesn't work for me because it returns values for invalid TLD's. For example it doesn't return nil for:

iex> PublicSuffix.registrable_domain("a.blahzzzzz")
"a.blahzzzzz"

Even though "blahzzzzz" is not a valid TLD. Although perhaps that's just a bug in registerable_domain/2?

[bkirz]

Interesting; it looks like we're falling back to the default rule in that case. This is correct according to the spec, but it makes the library substantially less useful. I like the public_suffix rubygem's approach of including a flag to disable the default rule:

irb(main):001:0> require 'public_suffix'
=> true
irb(main):002:0> PublicSuffix.valid?("a.blahzzzzz")
=> true
irb(main):003:0> PublicSuffix.valid?("a.blahzzzzz", default_rule: nil)
=> false

I'm thinking adding a similar option like PublicSuffix.registrable_domain("a.blahzzzzz", use_default_rule: false) to existing functions would make them better suited to your use case. How's that sound?

[axelson]

That would work great for me!

[andersju]

I know this issue is old, but since it's still open, I figure it might help someone else: sounds like the already existing matches_explicit_rule?/1 could help? E.g.:

iex(18)> PublicSuffix.matches_explicit_rule?("a.com")     
true
iex(19)> PublicSuffix.matches_explicit_rule?("a.blahzzzzz")                      
false

Of course simply "com" will also be true, but you could combine it with registrable_domain/1. Having a use_default_rule option would be handy though.

[axelson]

This is the function that we're currently using and it's been serving us well:

  def valid_tld?(%URI{host: host}) do
    # The checking is a little convoluted
    # Would be improved by https://github.com/seomoz/publicsuffix-elixir/issues/27
    rule = PublicSuffix.prevailing_rule(host)
    rule != "*" && rule != host
  end