Set categories on post if they appear in site frontmatter defaults

[tschmidt]

This pull request is the result of a discussion on #2343.

If category or categories were set in the site frontmatter defaults, they were not being picked up by the post when the site was being built. This was preventing the proper subdirectories from being built.

[parkr]

/cc @maul-esel

[tschmidt]

Hey guys, just dropping in to check on this. Any thoughts/feedback?

[parkr]

Why not value_from_singular_key(hash, singular_key) || value_from_plural_key(hash, plural_key)?

[tschmidt]

Unfortunately, that won't work because #value_from_singular_key() may return [] or [nil], which will be treated as true setting the array variable and skip the call to #value_from_plural_key().

The way that I interpreted the description for #pluralized_array_from_hash() is that if the singular key does not return a value (e.g. it returns [] or [nil]) then try the plural key.

I could update the code for #value_from_singular_key() and #value_from_plural_key() so that they return nil as a value - instead of an array - which would allow for the single line of code. I didn't want to do that though because I think the intent of the code is clearer with two lines.

I will defer to you guys as far as the coding style, though. Let me know what you prefer :)

[tschmidt]

For clarity, I've added a diff of what changes could be made to support a one-liner. I've also cleaned up the #pluralized_array_from_hash just a little by using the Object#tap method.

diff --git a/lib/jekyll/utils.rb b/lib/jekyll/utils.rb
index 6dab612..e1b4704 100644
--- a/lib/jekyll/utils.rb
+++ b/lib/jekyll/utils.rb
@@ -35,14 +35,13 @@ module Jekyll
       #
       # Returns an array
       def pluralized_array_from_hash(hash, singular_key, plural_key)
-        array = []
-        array << value_from_singular_key(hash, singular_key)
-        array << value_from_plural_key(hash, plural_key) if array.flatten.compact.empty?
-        array.flatten.compact
+        [].tap do |array|
+          array << (value_from_singular_key(hash, singular_key) || value_from_plural_key(hash, plural_key))
+        end.flatten.compact
       end

       def value_from_singular_key(hash, key)
-        [hash[key]] if hash.has_key?(key) || (hash.default_proc && hash[key])
+        hash[key] if (hash.has_key?(key) || (hash.default_proc && hash[key]))
       end

       def value_from_plural_key(hash, key)

[parkr]

Thanks for looking into it. Kind of wish value_from_singular_key would return nil if it's not there. In any even, I appreciate your [].tap solution. Just looking to be as functional as possible in Jekyll – it makes things a bit easier to read. 😄

[tschmidt]

After thinking about this more, I agree that value_from_singular_key should just return the value, or nil if it's not there. I'm going to go ahead and add the changes from the above diff. 😃

[parkr]

👍 😄

[parkr]

Cool, this looks good to me. Think we should update the documentation? Anything you can see in the configuration.md file that looks wrong to you?

[tschmidt]

I don't see anything that looks wrong. In the section about Front-matter defaults, it's not really mentioned that you can set the category or categories. Currently, only layout and author are being used as examples as to what you can set in the defaults array. We could add a comment specifically about specifying the categories as well, but I think that might be overkill since you should technically be able to set any key/value pair there.

[parkr]

Maybe you can add a note about the cascade?

[tschmidt]

Will do. I'll push that sometime tomorrow.

[parkr]

Awesome, thanks! We're trying to make sure master's docs are consistent with master's code. 😄 Also, this plural vs. singular stuff is a bit confusing without diving into the code, so it's always good to have a little extra help when reading up on it.

[parkr]

If you wouldn't mind following up with some docs, that'd be ⭐!