I learned a lot from working on a Forem issue, where comments containing Comment Liquid Tags were rendered invalid if the tagged comment was later deleted.
Yes. That was a mouthful.
I created a walkthrough video sharing my troubleshooting process. If you would rather read, I have reproduced my process below the video image. 😊
Say Arit creates a comment, and then Bene creates their comment and includes a Liquid Tag to Arit's comment:
Next, Arit deletes her comment. When Bene goes to edit her comment containing the tag to Arit's now-deleted comment, she sees an error message. Also, the permalink to Bene's comment 404's.
Looking in the code, the app > liquid_tags > comment_tag.rb file initializes and renders the tagged comment. The app > views > comments > _liquid.html.erb file is the actual tagged-comment view.
Looking at the find_comment method in comment_tag.rb, we see that the error message raised by the exception matches what we see in the application:
def find_comment(id_code)
Comment.find(id_code.to_i(26))
rescue ActiveRecord::RecordNotFound
raise StandardError, "Invalid comment ID or comment does not exist"
end
Intuitively, I felt like a good solution would be to return a message like "Comment Not Found" within the Liquid Tag, while leaving the enclosing comment intact. But I was not sure how to bypass the error exception in order to accomplish this.
After a short tete-a-tete with my teammate Rhymes (🙏🏾), I learned a key difference between the .find and .find_by methods: if the record is not found, .find always raises an exception while .find_by returns nil.
By calling .find_by, I could then render different views in _liquid.html.erb, depending on whether the local comment variable (passed into the render method) existed.
def find_comment(id_code)
Comment.find_by(id_code.to_i(26))
end
<div class="liquid-comment">
<% if comment %>
<div class="details">
<a href="/<%= comment.user.username %>">
...
...
<% else %>
<div class="body">
<p>Comment Not Found</p>
</div>
<% end %>
</div>
But when I tested my implementation, I got another error:
Unsupported argument type: 53 (Integer)
The only code I changed that accepts an argument was the find_comment method. I realized that .find_by requires me to specify which attribute to search by. Furthermore, the Comment.id_code attribute is a string, not an integer. So I made the appropriate corrections:
def find_comment(id_code)
Comment.find_by(id_code: id_code)
end
Testing my local application, everything worked as expected 🎉:
Figuring out how to solve a certain coding problem is sometimes akin to detective work. 🔎 You use the clues provided in the codebase (or by other devs) to figure out what needs to be changed, and where.
I hope this was helpful to someone. 😄 Thanks for reading/watching!
Cover Photo by Meghan Schiereck on Unsplash
Top comments (5)
I love this!!! I especially love how you talked through your thought process. This is going to be an invaluable resource to someone who wants to know how to tackle a new issue in an unfamiliar part of the codebase! Awesome job 👏
Thank you Vaidehi!! Your support means so much to me ☺️
Awesome write up :-)
This is a great post! I'm just discovering the Forem project and this is a great little introduction =)
I'm glad it's helpful Robert! Welcome to Forem! ☺️