TIL

• Comparing Go errors

  In a Go-based backend service, I update my dependencies. Notably, cloud.google.com/go/storage updated from v1.43.0 to v1.51.0. After deploying, I noticed a werid bug that wasn't happening before. I traced the problem to following code:

  import (
      // ...
      gcs "cloud.google.com/go/storage"
      // ...
  )
  
  // ...
  if err == gcs.ErrObjectNotExist {
      // ...
  }
  

  Situations that would previously trigger this conditionally, no longer were. Upon further digging, Google wants you to compare these errors using errors.Is(). This fixed the bug:

  if errors.Is(err, gcs.ErrObjectNotExist) {
      // ...
  }
  

  Worried, I checked other error checking comparisons (specifically io.EOF) and found this comment above the definition of EOF:

  // EOF is the error returned by Read when no more input is available.
  // (Read must return EOF itself, not an error wrapping EOF,
  // because callers will test for EOF using ==.)
  

  So it looks like in those cases, they prepared for that scenario.

  09 Apr 2025

  • error checking
  • Go

• Listing Variables Within a Jinja2 Template

  While converting this site to Pelican, I needed to do quite a bit of plugin and template writing to get it to look and feel the way I wanted to. One frustration was not knowing which variables I had available to my templates. After quite a few failed attempts and bad advice from some LLMs, ChatGPT offered this solution which worked for me:

  <ul>
    {% for key, value in self.__dict__.items() %}
      <li>{{ key }}: {{ value }}</li>
    {% endfor %}
  </ul>
  

  To be clear, though, ChatGPT offered several solutions, some of which were incorrect or bad... this one happened to work though.

  04 Apr 2025

  • Jinja2
  • Pelican