Jupyter Book: Fixing Confusing `extends` Error Messages

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Jupyter Book: When extends Doesn't Resolve its Target Properly, the Error Message is Hard to Parse

Hey guys,

Let's dive into making error messages in Jupyter Book and MySTmd a whole lot friendlier, especially when things go wrong with the extends configuration. Currently, if the URL specified in extends: points to a file that can't be found or accessed, the error message is quite cryptic. This can leave you scratching your head trying to figure out what went wrong.

The Problem: Cryptic Error Messages

When the extends: config in your Jupyter Book or MySTmd setup points to a URL that doesn't resolve properly, the error message you get isn't exactly user-friendly. It's like trying to decipher ancient code! Instead of clearly stating the problem, it throws a bunch of technical jargon at you, making it hard to pinpoint the root cause. This is especially frustrating for beginners who are just getting started with these tools.

Here's a breakdown of the issues:

  1. Error Message Placement: The most relevant part of the error message, which should be a human-readable explanation, is often buried at the top of the output. This means you have to wade through a lot of technical details before you even understand the basic problem.
  2. Obscured URL: The broken URL, which is the key to solving the issue, is also located at the top. It should be placed at the bottom where it's easily visible and accessible.
  3. Lack of Clarity: The error message doesn't explicitly state that the problem is due to the extends: configuration failing to resolve the target file. This lack of clarity can lead to confusion and wasted time as users try to debug the issue.

For example, you might see an error message like this:

Cache file not found: /home/runner/work/blog/blog/_build/cache/config-item-ef6fa4542542f1c9f23f1e258817ad8f.yml
Fetching: https://raw.githubusercontent.com/jupyter-book/jupyter-book/refs/heads/next/docs/site.yml
Bad response from config URL: https://raw.githubusercontent.com/jupyter-book/jupyter-book/refs/heads/next/docs/site.yml
/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291472
    throw Error(`Cannot find config file: ${file}`);
          ^

Error: Cannot find config file: /home/runner/work/blog/blog/_build/cache/config-item-ef6fa4542542f1c9f23f1e258817ad8f.yml
    at loadConfigYaml (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291472:11)
    at getValidatedConfigsFromFile (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291532:35)
    at /opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291567:60
    at Array.map ()
    at getValidatedConfigsFromFile (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291559:79)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)
    at async loadConfig (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291611:46)
    at async findCurrentProjectAndLoad (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:291781:5)
    at async _Session.reload (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:333085:5)
    at async _Command. (/opt/hostedtoolcache/node/20.19.5/x64/lib/node_modules/mystmd/dist/myst.cjs:333215:5)

See? Not exactly a walk in the park to decipher. It's like the error message is playing hide-and-seek with the important information. Therefore, it's imperative to enhance these error messages.

Proposed Improvements: Making Errors Human-Friendly

So, how can we make these error messages more helpful? Here are a few ideas:

  1. Prioritize Human-Readable Messages: Move the human-friendly error message to the very bottom of the output. This way, it's the first thing you see, giving you a clear understanding of the problem right away. The technical details can still be there, but they shouldn't be the first thing you encounter.
  2. Highlight the Broken URL: Move the broken URL to the bottom as well, making it easy to spot. Maybe even highlight it or add a clear label like "The following URL could not be resolved:" This makes it super easy to identify the problematic URL and correct it.
  3. Be Explicit About extends:: Explicitly state that the error is a result of the extends: configuration not pointing to the correct file. For example, you could add a line like, "This error occurred because the URL specified in your extends: configuration could not be found." This leaves no room for ambiguity.

By implementing these improvements, we can transform cryptic error messages into helpful guides that lead users to a quick resolution. This will improve user experience significantly.

Example Scenario

Let's say you're working on a Jupyter Book project and you have the following in your _config.yml file:

extends: https://raw.githubusercontent.com/jupyter-book/jupyter-book/refs/heads/next/docs/site.yml

Now, imagine that this URL is temporarily unavailable or has been moved. Currently, you'd get the confusing error message we discussed earlier. But with our proposed improvements, the error message could look something like this:

[Technical details and stack trace]

Error: The URL specified in your `extends:` configuration could not be resolved.
Please check the URL and ensure that it points to a valid YAML file.

The problematic URL is:
https://raw.githubusercontent.com/jupyter-book/jupyter-book/refs/heads/next/docs/site.yml

See the difference? Much clearer, right? It directly tells you what the problem is and where to look for the solution.

Why This Matters: Improving the User Experience

Making error messages more user-friendly is crucial for a number of reasons:

  • Reduces Frustration: Clear error messages help reduce frustration and prevent users from giving up on the tool. When people can easily understand what went wrong and how to fix it, they're more likely to stick with the project and continue learning.
  • Saves Time: By providing clear and concise information, we can save users valuable time. Instead of spending hours trying to decipher cryptic error messages, they can quickly identify the problem and implement a solution.
  • Enhances Learning: User-friendly error messages can also serve as a learning tool. By explaining the problem in simple terms, we can help users understand the underlying concepts and avoid making the same mistake in the future.
  • Promotes Adoption: A positive user experience is essential for promoting the adoption of Jupyter Book and MySTmd. When people find these tools easy to use and understand, they're more likely to recommend them to others.

Real-World Example: GitHub Actions

Here's a real-world example of this issue in action. In this GitHub Actions run, the error message caused confusion and made it difficult to diagnose the problem:

https://github.com/jupyter-book/blog/actions/runs/19107760298/job/54596225577

By implementing the proposed improvements, we can prevent similar issues in the future and make the debugging process much smoother.

Conclusion: Let's Make Error Messages Our Friends

In conclusion, improving error messages in Jupyter Book and MySTmd is a small change that can have a big impact. By prioritizing human-readable messages, highlighting broken URLs, and being explicit about the cause of the error, we can create a more user-friendly and enjoyable experience for everyone. Let's turn those cryptic error messages into helpful guides that empower users to solve problems quickly and efficiently. So next time you're working with Jupyter Book or MySTmd, remember that clear error messages are your friends, not your enemies!