Jekyll Implicit Conversion Error
Jekyll Error “no implicit conversion of nil into String”
The Problem
While trying to create a new Jekyll website to host on GitHub pages I tried using a remote theme which I have done in the past (For this blog in fact). But when setting the theme and remote_theme configuration variables to the remote theme in _config.yml it resulted in the following error
Configuration file: /Users/bkelley/dev/site/_config.yml
jekyll 3.8.6 | Error: no implicit conversion of nil into String
Leaving the theme configuration variable as the default minima theme, this error does not occur and everything builds and serves as expected.
Jekyll Doctor
The first thing I tried was to run the jekyll doctor command to check the configuration file.
jekyll doctor
This resulted in the same error message
Configuration file: /Users/bkelley/dev/site/_config.yml
jekyll 3.8.6 | Error: no implicit conversion of nil into String
If the command was successful, it give the following message
Configuration file: /Users/bkelley/dev/site/_config.yml
Your test results are in. Everything looks fine.
Verbose Build
bundle exec jekyll build --verbose
Resulted in the following result
Logging at level: debug
Configuration file: /Users/bkelley/dev/jessica/_config.yml
Theme: freelancer-theme-jekyll
Theme source: /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/freelancer-theme-jekyll-1.0.0
Requiring: jekyll-paginate
Requiring: jekyll-sitemap
Requiring: jekyll-gist
Requiring: jekyll-feed
Requiring: jekyll-data
Requiring: jemoji
Requiring: jekyll-feed
jekyll 3.8.6 | Error: no implicit conversion of nil into String
Stack Trace
jekyll build --trace
Resulted in the following result
Configuration file: /Users/bkelley/dev/jessica/_config.yml
Traceback (most recent call last):
20: from /Users/bkelley/.rvm/gems/ruby-2.6.3/bin/ruby_executable_hooks:24:in `<main>`
19: from /Users/bkelley/.rvm/gems/ruby-2.6.3/bin/ruby_executable_hooks:24:in `eval`
18: from /Users/bkelley/.rvm/gems/ruby-2.6.3/bin/jekyll:23:in `<main>`
17: from /Users/bkelley/.rvm/gems/ruby-2.6.3/bin/jekyll:23:in `load`
16: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/exe/jekyll:15:in `<top (required)>`
15: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/mercenary-0.3.6/lib/mercenary.rb:19:in `program`
14: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/mercenary-0.3.6/lib/mercenary/program.rb:42:in `go`
13: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `execute`
12: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `each`
11: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/mercenary-0.3.6/lib/mercenary/command.rb:220:in `block in execute`
10: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/commands/build.rb:18:in `block (2 levels) in init_with_program`
9: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/commands/build.rb:30:in `process`
8: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/commands/build.rb:30:in `new`
7: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/site.rb:34:in `initialize`
6: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/hooks.rb:102:in `trigger`
5: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/hooks.rb:102:in `each`
4: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-3.8.6/lib/jekyll/hooks.rb:103:in `block in trigger`
3: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-data-1.1.0/lib/jekyll-data.rb:50:in `block in <top (required)>`
2: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-data-1.1.0/lib/jekyll-data.rb:50:in `new`
1: from /Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-data-1.1.0/lib/jekyll-data/reader.rb:10:in `initialize`
/Users/bkelley/.rvm/gems/ruby-2.6.3/gems/jekyll-data-1.1.0/lib/jekyll-data/reader.rb:10:in `join`: no implicit conversion of nil into String (TypeError)
The last line in the stack trace gives the file, line number, and function the error occurred in. Using this, I could go see the line and figure out why this error was occurring.
Tracking Down the Error
Using the stack trace I was able to get the file the error occurred in reader.rb in the jekyll-data plugin. Using VS Code, I was able to simply Cmd+click the line to follow it to the file, to the line that threw the error. You could do this by using the file explorer as well. In doing so, I was routed to this line:
@theme_data_files = Dir[File.join(site.theme.data_path, "**", "*.{yaml,yml,json,csv,tsv}")]
Based on the error message, the error occurred in the join function. Also, the error message stated o implicit conversion of nil into String and seeing that 2 of the 3 parameters passed to join were in fact strings, site.theme.data_path must be the culprit.
In doing some research on this issue seeing if anyone else had run into this, I came across an issue created in the jekyll-data plugin repository. There was an assumption that if you were using this plugin, your theme would have a _data directory so there wasn’t a null check on site.theme.data_path. This was resolved in v1.1.0.
The Jekyll theme that I was using did not have a _data directory at the root. Unfortunately adding a data directory at the root of my project did not fix this either. So I created an issue on the Jekyll theme to get a data directory added or get the dependency removed if unused.