Custom System Image Option For JETLS: A Feature Request

Dec 5, 2025 by Admin 56 views

Hey guys!

Let's dive into a cool feature request that could seriously boost the performance and reliability of your JETLS projects. We're talking about the ability to use custom system images. For those of you who aren't super familiar, a system image is essentially a precompiled snapshot of your Julia environment. Think of it like a super-efficient starting point for your code. Instead of rebuilding everything from scratch every time, Julia can load this image and get straight to work.

Why Custom System Images?

So, why would you even want to use a custom system image? Well, there are a bunch of really good reasons. First off, speed! Creating a custom image bakes in all your frequently used packages, so Julia doesn't have to waste time loading and compiling them every single time you run your script. This can lead to significant performance gains, especially for larger projects. Secondly, consistency! Custom system images ensure that everyone on your team is using the exact same package versions. No more "it works on my machine!" situations. This can be a lifesaver when you're collaborating on complex projects.

The Feature Request: Giving JETLS Custom Image Support

The core of this request is simple: let's add an option to JETLS that allows users to specify a custom system image to use. The user suggests being able to specify the relative file path, e.g. bin/kps-image-1.12-main.so. If the file doesn't exist, the setting should be ignored. This is a non-breaking change. If the custom image is provided and it exists, use it. Otherwise, ignore it. Simple and elegant.

Performance Improvements

One of the most compelling reasons for using custom system images is the potential for significant performance improvements. When you create a custom system image, you're essentially precompiling all of your project's dependencies into a single file. This means that Julia doesn't have to spend time loading and compiling these dependencies every time you run your code. This can be especially beneficial for large projects with many dependencies. The performance improvements can range from a few seconds to several minutes, depending on the size and complexity of your project. This can save you a lot of time and frustration, especially if you're working on a large project with many dependencies. You will no longer have to wait for Julia to compile your code every time you run it. You can simply load the custom system image and get straight to work.

Ensuring Correct Package Versions

Another key advantage of using custom system images is that they can help ensure that everyone on your team is using the same package versions. This can be a lifesaver when you're collaborating on complex projects. When you create a custom system image, you're essentially creating a snapshot of your project's dependencies. This means that everyone who uses the image will be using the exact same package versions. This can help prevent the dreaded "it works on my machine!" situation. By including specific package versions in your system image, you ensure that your project runs consistently across different environments. This is crucial for reproducibility and collaboration.

How It Could Work: A Potential Implementation

So, how could this feature actually be implemented in JETLS? Here's one possible approach:

Configuration Option: Add a new option to the JETLS configuration file (e.g., jetls.toml) that allows users to specify the path to their custom system image. This could look something like this:
```
system_image = "bin/my_custom_image.so"
```
Path Handling: JETLS would need to handle relative and absolute paths correctly. Relative paths would be resolved relative to the project root.
Image Loading: When JETLS starts, it would check if the specified system image file exists. If it does, JETLS would load the image. If it doesn't, JETLS would fall back to the default system image.
Error Handling: If there's an error loading the custom system image (e.g., the file is corrupted), JETLS should display a clear error message and gracefully fall back to the default system image.

Implementation Details

Let's break down those steps a bit further.

Configuration Option: The jetls.toml file would need to be updated to include a new system_image option. This option would allow users to specify the path to their custom system image. The path could be relative or absolute. If the path is relative, it should be resolved relative to the project root. This allows users to easily specify the location of their custom system image without having to worry about absolute paths.

Path Handling: JETLS would need to be able to handle both relative and absolute paths. This is important because users may store their custom system images in different locations. If the path is relative, JETLS would need to resolve it relative to the project root. This ensures that JETLS can find the custom system image, regardless of where it is stored.

Image Loading: When JETLS starts, it would check if the specified system image file exists. If it does, JETLS would load the image. If it doesn't, JETLS would fall back to the default system image. This ensures that JETLS can always start, even if the custom system image is not available.

Error Handling: If there's an error loading the custom system image (e.g., the file is corrupted), JETLS should display a clear error message and gracefully fall back to the default system image. This prevents JETLS from crashing if there is a problem with the custom system image. Instead, JETLS will simply fall back to the default system image and continue to run.

Benefits of This Feature

Improved Performance: Faster startup times and overall execution speed.
Increased Consistency: Ensures everyone is using the same package versions.
Simplified Project Management: Easier to manage dependencies and environments.
Enhanced Reproducibility: Makes it easier to reproduce results across different machines.

Simplified Project Management

Custom system images can also simplify project management. By including all of your project's dependencies in a single file, you can make it easier to manage your project's dependencies. This can be especially helpful for large projects with many dependencies. You can easily share your project with others by simply sharing the custom system image. This eliminates the need for others to install all of the project's dependencies manually.

Enhanced Reproducibility

Finally, custom system images can enhance reproducibility. By including specific package versions in your system image, you ensure that your project runs consistently across different environments. This is crucial for reproducibility and collaboration. It ensures that your project will produce the same results, regardless of where it is run.

Conclusion

Adding support for custom system images in JETLS would be a fantastic addition. It would offer significant performance benefits, improve consistency, and simplify project management. It's a win-win for everyone! Let's hope the JETLS developers consider this feature request. It would make a lot of Julia developers very happy.

What do you guys think? Let me know in the comments below!