undefined method `nil_or_empty?' for String

[nfrankel]

Hello,

I'm trying to make Jekyll excerpts work, but I unfortunately come upon this trace:

Conversion error: Jekyll::AsciiDoc::Converter encountered an error while converting '_posts/2012-03-11-html5-still-a-non-event.adoc':
                    undefined method `nil_or_empty?' for #<String:0x007fa72f7dfdb0>
  Liquid Exception: undefined method `nil_or_empty?' for #<String:0x007fa72f7dfdb0> in tag/html-5/index.html
/Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-asciidoc-2.0.1/lib/jekyll-asciidoc/converter.rb:207:in `convert': undefined method `nil_or_empty?' for #<String:0x007fa72f7dfdb0> (NoMethodError)
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:109:in `block in convert'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:107:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:107:in `reduce'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:107:in `convert'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:86:in `run'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/excerpt.rb:72:in `output'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/excerpt.rb:59:in `to_s'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/drops/document_drop.rb:22:in `excerpt'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/drops/drop.rb:52:in `public_send'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/drops/drop.rb:52:in `[]'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/context.rb:201:in `lookup_and_evaluate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/variable_lookup.rb:48:in `block in evaluate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/variable_lookup.rb:38:in `each_index'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/variable_lookup.rb:38:in `evaluate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/context.rb:168:in `evaluate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/context.rb:160:in `[]'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/condition.rb:101:in `interpret_condition'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/condition.rb:39:in `evaluate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/if.rb:38:in `block (2 levels) in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/if.rb:37:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/if.rb:37:in `block in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/context.rb:132:in `stack'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/if.rb:36:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:151:in `render_token'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler/hooks.rb:5:in `block in render_token_with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler.rb:80:in `profile_token_render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler/hooks.rb:4:in `render_token_with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:135:in `block in render_all'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:122:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:122:in `render_all'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:108:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:210:in `block in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:262:in `with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:209:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:222:in `render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:28:in `block (2 levels) in render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:40:in `measure_bytes'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:27:in `block in render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:47:in `measure_time'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:26:in `render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/tags/include.rb:138:in `block in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/context.rb:132:in `stack'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/tags/include.rb:136:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:151:in `render_token'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler/hooks.rb:5:in `block in render_token_with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler.rb:80:in `profile_token_render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler/hooks.rb:4:in `render_token_with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:135:in `block in render_all'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:122:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:122:in `render_all'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/for.rb:113:in `block (2 levels) in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/for.rb:100:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/for.rb:100:in `each_with_index'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/for.rb:100:in `block in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/context.rb:132:in `stack'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/tags/for.rb:99:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:151:in `render_token'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler/hooks.rb:5:in `block in render_token_with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler.rb:80:in `profile_token_render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/profiler/hooks.rb:4:in `render_token_with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:135:in `block in render_all'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:122:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:122:in `render_all'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/block.rb:108:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:210:in `block in render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:262:in `with_profiling'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:209:in `render'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/liquid-3.0.6/lib/liquid/template.rb:222:in `render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:28:in `block (2 levels) in render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:40:in `measure_bytes'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:27:in `block in render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:47:in `measure_time'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/liquid_renderer/file.rb:26:in `render!'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:134:in `render_liquid'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/renderer.rb:82:in `run'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/convertible.rb:211:in `do_layout'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/page.rb:135:in `render'
	from /Users/i303869/projects/private/nfrankel.gitlab.io/_plugins/tags.rb:43:in `write_tag_index'
	from /Users/i303869/projects/private/nfrankel.gitlab.io/_plugins/tags.rb:36:in `block in generate'
	from /Users/i303869/projects/private/nfrankel.gitlab.io/_plugins/tags.rb:35:in `each'
	from /Users/i303869/projects/private/nfrankel.gitlab.io/_plugins/tags.rb:35:in `generate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/site.rb:174:in `block in generate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/site.rb:172:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/site.rb:172:in `generate'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/site.rb:68:in `process'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/command.rb:26:in `process_site'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/commands/build.rb:63:in `build'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/commands/build.rb:34:in `process'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/lib/jekyll/commands/serve.rb:37:in `block (2 levels) in init_with_program'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `call'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `block in execute'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `each'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `execute'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in `go'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/mercenary-0.3.6/lib/mercenary.rb:19:in `program'
	from /Users/i303869/.rbenv/versions/2.2.3/lib/ruby/gems/2.2.0/gems/jekyll-3.3.1/exe/jekyll:13:in `<top (required)>'
	from /usr/local/bin/jekyll:22:in `load'
	from /usr/local/bin/jekyll:22:in `<main>'

I'm using:

• Ruby 2.2.3
• Jekyll 3.3.1
• jekyll-asciidoctor plugin 2.0.1

Interestingly enough, it works if:

• Either I remove *.adoc files
• Or don't try to write excerpts

Hints welcome, many thanks.

[mojavelinux]

I'll need to investigate to see how the call chain is arriving at this point. However, what I can tell you is that the excerpts in Jekyll are extremely problematic, esp when used with this plugin. In my opinion, they are very poorly done and hard to accommodate in extensions. Filters don't get applied to them, and there is no way to know what document they came from. Therefore, we don't have a good opportunity to prepare them properly. My recommendation is to avoid using them and instead have your own way of doing excerpts. We may end up providing an alternative excerpt mechanism for AsciiDoc documents in this plugin.

[nfrankel]

Thanks for your feedback. So far, I'm living without excerpts and I've no clue how they are coded - I'm not a Ruby developer, thus I believe you. However, from a functional point of view, my home page is very long and would benefit from excerpts.

Whatever you can provide is good enough for me.

[theaspect]

Same issue for me

~/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/jekyll-asciidoc-2.0.1/lib/jekyll-asciidoc/converter.rb:207:in `convert': undefined method `nil_or_empty?' for #<String:0x007f8f67371a88> (NoMethodError)
	from ~/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/jekyll-3.4.1/lib/jekyll/renderer.rb:109:in `block in convert'
	from ~/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/jekyll-3.4.1/lib/jekyll/renderer.rb:107:in `each'
	from ~/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/jekyll-3.4.1/lib/jekyll/renderer.rb:107:in `reduce'
	from ~/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/jekyll-3.4.1/lib/jekyll/renderer.rb:107:in `convert'
	from ~/.rbenv/versions/2.1.5/lib/ruby/gems/2.1.0/gems/jekyll-3.4.1/lib/jekyll/renderer.rb:86:in `run'
...

[mojavelinux]

Try as I might, I cannot reproduce this. What I am trying to figure out is how the object being passed to convert is not a String. If it's a String, it should have the nil_or_empty? method because it is added to String by Asciidoctor. However, in the event that it is not a String, it makes sense why it would not find this method. I just can't figure out how that's happening.

Can you please share a site that demonstrates this problem so that I may study it? I know that switching from nil_or_empty? would fix it, but it would also mean that we cannot assume that we're getting a String. And I need to know what that's all about before I make this fix.

[mojavelinux]

However, from a functional point of view, my home page is very long and would benefit from excerpts.

Could you provide more details about how you are defining your excerpts? Are you defining them using page-excerpt or are you depending on the auto-extract feature? That feature definitely still needs work in the plugin...if I can wrap my head around the mess that Jekyll has made.

[nfrankel]

I tried again. I didn't do configure anything so that the excerpt is the default one (probably the body itself). Then in my layout, I call {post.excerpt}.

But I pinpointed the cause of the error in a Ruby plugin. If I remove the plugin, it works. If I remove some tags for some posts, it works also. I don't know why, I have 0 in Ruby knowledge.

#From https://github.com/arocks/arunrocks
module Jekyll

  class TagIndex < Page
    def initialize(site, base, dir, tag)
      @site = site
      @base = base
      @dir = dir
      @name = 'index.html'
      self.process(@name)
      self.read_yaml(File.join(base, '_layouts'), 'tag.html')
      self.data['tag'] = tag
Jekyll.logger.info "tag #{tag}"
      self.data['related'] = []
      site.tags[tag].each do |post|
        post.data['tags'].each do |rel| 
          self.data['related'].push(rel)
        end
      end
      self.data['related'] = self.data['related'].uniq
      tag_title_prefix = site.config['tag_title_prefix'] || 'Tags: '
      self.data['title'] = "#{tag_title_prefix}#{tag}"
      self.data['sitemap'] = true
    end
  end

  class TagGenerator < Generator
    safe true
    priority :high
    
    def generate(site)
      if site.layouts.key? 'tag'
        dir = site.config['tag_dir'] || 'tag'
        site.tags.keys.each do |tag|
          write_tag_index(site, File.join(dir, tag.gsub(/\s/, "-").gsub(/[^\w-]/, '').downcase), tag)
        end
      end
    end
  
    def write_tag_index(site, dir, tag)
      index = TagIndex.new(site, site.source, dir, tag)
      index.render(site.layouts, site.site_payload)
      index.write(site.dest)
      site.static_files << index
    end
  end
end

[mojavelinux]

As I said, I understand why it's happening. It's an ordering issue. I just don't know what exactly is triggering it (aside from generally this plugin, which we already suspect).

Is there any way you can share a minimal project that fails in the same way? (or give me access to your site's repository?) There is a complex interaction between plugins that I need to understand in order to know how to fix it.

[mojavelinux]

I also think I understand now how to make excerpts work correctly...or at least I have an idea. But I need to test that theory.

[nfrankel]

My project is hosted on Gitlab. Please create an account, give me its handle and I'll give you access.

[mojavelinux]

My account on GitLab is mojavelinux also. (https://gitlab.com/mojavelinux)

[nfrankel]

I granted you access rights. I suggest you use branch features/new-posts because master has a lot of posts and generation takes a lot of time.

[mojavelinux]

Great! I'll have a look.

[DanielSWolf]

Any news on this? I'm trying to write an AsciiDoctor plugin, and it's failing as soon as my class calls use_dsl, because use_dsl executes self.name.nil_or_empty?.

jekyll 3.5.1 | Error: undefined method `nil_or_empty?' for "CustomAdmonitionBlock":String

At that point, self.name appears to be a String, but it doesn't have a method nil_or_empty. To be sure, I added the following debugging code:

class CustomAdmonitionBlock < Asciidoctor::Extensions::BlockProcessor
  puts 'value: ' + self.name
  puts 'class: ' + self.name.class.to_s
  puts 'methods: ' + self.name.methods.sort.join(', ')
  puts 'responds to `nil_or_empty?`: ' + self.name.respond_to?(:nil_or_empty?).to_s
end

Output:

value: CustomAdmonitionBlock
class: String
methods: !, !=, !, %, *, +, +@, -@, <, <<, <=, <=>, ==, ===, =, >, >=, [], []=, id, send, ansi_jump, ascii_only?, b, between?, black, blue, bold, bytes, bytesize, byteslice, capitalize, capitalize!, casecmp, center, chars, chomp, chomp!, chop, chop!, chr, class, clear, clear_line, clear_screen, clone, codepoints, colorize, concat, count, crypt, cyan, define_singleton_method, delete, delete!, display, downcase, downcase!, dump, dup, each_byte, each_char, each_codepoint, each_line, empty?, encode, encode!, encoding, end_with?, enum_for, eql?, equal?, extend, force_encoding, freeze, frozen?, gem, getbyte, green, gsub, gsub!, has_ansi?, has_color?, hash, hex, include?, index, insert, inspect, instance_eval, instance_exec, instance_of?, instance_variable_defined?, instance_variable_get, instance_variable_set, instance_variables, intern, is_a?, itself, kind_of?, length, lines, ljust, lstrip, lstrip!, magenta, match, method, methods, next, next!, nil?, object_id, oct, ord, parse_csv, partition, prepend, private_methods, protected_methods, psych_to_yaml, public_method, public_methods, public_send, red, remove_instance_variable, replace, reset_ansi, reset_color, respond_to?, reverse, reverse!, rindex, rjust, rpartition, rstrip, rstrip!, scan, scrub, scrub!, send, setbyte, singleton_class, singleton_method, singleton_methods, size, slice, slice!, split, squeeze, squeeze!, start_with?, strip, strip!, strip_ansi, strip_color, sub, sub!, succ, succ!, sum, swapcase, swapcase!, taint, tainted?, tap, to_c, to_enum, to_f, to_i, to_json, to_json_raw, to_json_raw_object, to_liquid, to_r, to_s, to_str, to_sym, to_yaml, to_yaml_properties, tr, tr!, tr_s, tr_s!, trust, unicode_normalize, unicode_normalize!, unicode_normalized?, unpack, untaint, untrust, untrusted?, upcase, upcase!, upto, valid_encoding?, white, yellow
responds to nil_or_empty?: false