Cover image for Forem Issue Walkthrough: Comment Liquid Tags πŸ’¬

Forem Issue Walkthrough: Comment Liquid Tags πŸ’¬

msarit profile image Arit Amana Updated on ・3 min read

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. 😊

Image of Video

Say Arit creates a comment, and then Bene creates their comment and includes a Liquid Tag to Arit's comment:

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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.

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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)
rescue ActiveRecord::RecordNotFound
   raise StandardError, "Invalid comment ID or comment does not exist"

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 (πŸ™πŸΎ), 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)
<div class="liquid-comment">
  <% if comment %>
    <div class="details">
      <a href="/<%= comment.user.username %>">
  <% else %>
    <div class="body">
      <p>Comment Not Found</p>
  <% end %>

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)

Testing my local application, everything worked as expected πŸŽ‰:

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Figuring out how to solve a certain coding problem is sometimes akin to detective work. πŸ”Ž 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. πŸ˜„ Thanks for reading/watching!

Cover Photo by Meghan Schiereck on Unsplash

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msarit profile

Arit Amana


Software Engineer. Former Public Health Analyst. Coding Bootcamp Grad. Mentor to aspiring and early-career female devs.


Editor guide

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 πŸ‘


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! ☺️