Adding new Slugify.generate method to generate a slug value

[jwoertink]

Fixes #813

This method will generate a String value that can be used for a slug, but without setting any attribute value for you. This would be more used for an escape hatch than anything. Since it's not passing in the slug column, there's no way to query to know if it's been taken already. This means we can't do the query lookup to ensure the value is unique.

before_save do
  if title.changed?
    slug.value = Avram::Slugify.generate(using: title)
  end

  validate_uniqueness slug, query: ArticleQuery.new.slug
end

[jwoertink]

turns out this was a duplicate spec with the one right above it.

[matthewmcgarvey]

Not sure how useful it would be without the ability to check the slug in the database. another option would be to pass in everything like the other method but not to check the value. Or maybe just the column name instead of the whole attribute but that might be confusing

[jwoertink]

Yeah, I was kind of stumped on this one too. I went back and forth with it a few times and finally just said I'll push something up so we can hash it out.

I agree passing in just the column name might be confusing, and we'd lose the type-safety there anyway.

Maybe what we could do is something like..

def set(...)
  if slug.value.blank?
    slug.value = generate(...)
  end
end

and just have generate handle the logic ... 🤔

[robacarp]

Should this include a call to #strip as well?

[robacarp]

A uuid fallback would not be my expectation here, but I'm not sure what would have been my expectation. A slug is usually designed to be more "human friendly" than a UUID... so I think I'd just expect it to raise if it couldn't build a slug.

[robacarp]

What's this line do? Is it proving a compile time check?

[jwoertink]

I put it there just to make sure you were awake 😛 actually, it's just a copy/paste error. I need to remove it 😅

[jwoertink]

Alright, here's an update that moves all of the logic to generate. Then set just looks to see if the slug has a value already and if not, calls generate to set it.

I started to add in an error and have generate raise the error if no slug could be generated, but then I saw this spec

avram/spec/avram/slugify_spec.cr

Lines 101 to 111 in c798fbb

	describe "all slug candidates are blank" do
	it "leaves the slug as nil" do
	op = build_op(title: "")
	# First string is empty. Added to make sure it is not used with
	# the UUID.
	slugify(op.slug, ["", op.title])
	op.slug.value.should be_nil
	end
	end

basically this allows it to be nil. I decided that does make sense because it would be up to you to add in the validations if this field was required or not. So I turned generate in to String? which just returns nil if no slug is generated.

[matthewmcgarvey]

This needs to be updated I think