In this post, I share an intriguing issue I encountered while working with a GitHub Client library, a tool designed to simplify interactions with GitHub's RESTful API. This experience offered me a deeper understanding of REST APIs, particularly GitHub's implementation, which features a remarkably detailed approach with HATEOAS (Hypermedia as the Engine of Application State) atop its services.

The Initial Problem

While utilizing the GitHub API, I stumbled upon an issue when attempting to fetch file contents from a repository. The error message was quite cryptic:

Unrecognized Encoding: None

Determined to resolve this, I dove into the problem, considering recent changes in my business logic that might have introduced encoding issues during file writes. However, after comparing the logic before and after these changes, it was clear that the writing process hadn't been altered, leaving me back at square one.

Investigating Further

My next step was to check the GitHub API Official Documentation, hoping to find clues or discrepancies in my approach.

Uncovering the Cause

It turns out, the GitHub API has specific guidelines for accessing file contents based on file size. For small files, accessing content via the application/json MediaType is straightforward and poses no issues. However, this method doesn't apply to files larger than 1MB. Instead, GitHub requires a specific custom MediaType for such cases.

By sending the file content request with the vnd.github.raw MediaType, I could successfully retrieve the file content. This discovery was pivotal and resolved the issue entirely. Here's a curl command that exemplifies this solution:

curl -L \
  -H "Accept: application/vnd.github+json" \
  -H "Authorization: Bearer <YOUR-TOKEN>"\
  -H "X-GitHub-Api-Version: 2022-11-28" \
  https://api.github.com/repos/OWNER/REPO/contents/PATH

Understanding the MediaType Restriction

The requirement for different MediaTypes based on file size stems from practical constraints. While 'application/json' is adept at handling straightforward responses, it's ill-suited for transferring large files, which could incur significant file I/O and network costs. Conversely, for small files, encoding the contents with 'application/json' is entirely feasible.

The distinction is further highlighted in file transfers:

• Client-to-server transfers utilize 'multipart' file uploads.
• Servers can return files as InputStream or ByteArrayResource, facilitating client downloads.

The prefix 'vnd' in MIME types denotes a vendor-specific format, while 'prs' signifies a personalized MIME type, as explained in these StackOverflow discussions: MIME types and downloading files from a Spring Boot REST service (you can do similar for GoLang, this discussion was good for learning).

Conclusion

The encounter with the 'Unrecognized Encoding' error was not only a lesson in debugging but also an insightful dive into the functionalities and limitations of the GitHub API. It underscores the importance of understanding the tools and protocols we use daily and reminds us that sometimes, the solution lies in the details we often overlook.