Enhancing Shibuya Theme With Pygments Extension Support A Comprehensive Guide
Introduction
Hey guys! I'm diving deep into enhancing the Shibuya theme, and I've hit a snag with Pygments extension support. I'm super excited about Shibuya; it's a fantastic theme for my projects. However, I've run into an issue with custom Pygments lexers not being recognized. I'm working on a project that provides utilities for rendering Click based CLIs in Sphinx documentation. Specifically, I use two custom Sphinx directives, click:example and click:run, which generate code-block directives. One of these directives renders code-block using a custom Pygments language called ansi-shell-session. This allows me to render ANSI characters in a shell session, simulating the execution of a Click CLI. These custom formatters, filters, and lexers are properly registered to Pygments as plugins. This is crucial for providing a realistic and interactive documentation experience for users. The ability to display ANSI-colored output in code blocks makes the documentation much more engaging and easier to follow. Without this, the rendered output loses its visual cues, making it harder for users to understand the behavior of the CLI.
The Problem: Custom Pygments Lexers Not Recognized in Shibuya
The core issue I'm facing is that Shibuya doesn't seem to pick up these custom Pygments lexers. So, when I use a code block like this:
```{code-block} ansi-shell-session
$ my-cli
<my CLI output>
Instead of rendering with the ansi-shell-session lexer, the code block is rendered as plain text. This is not ideal, as it loses the syntax highlighting and formatting that makes the code more readable and understandable. This custom language is essential for rendering ANSI characters in shell sessions, which simulate the execution of a Click CLI. This functionality is part of my project, which provides utilities to render Click-based CLIs in Sphinx documentation. The custom lexer ensures that the ANSI characters are correctly interpreted and displayed, preserving the visual cues that are crucial for understanding the output of the CLI. Without the custom lexer, the ANSI characters would be rendered as plain text, making it difficult for users to interpret the output. This is a significant issue because it affects the usability and clarity of the documentation. The custom lexer allows for a more accurate and engaging representation of the CLI's behavior, which is crucial for users who rely on the documentation to learn how to use the CLI effectively. The lack of proper highlighting and formatting can lead to confusion and frustration, ultimately hindering the user's ability to understand and utilize the CLI.
Root Cause: Static Pygments CSS File
My suspicion is that the problem lies in Shibuya's use of a static Pygments CSS file. This means that the CSS styles for Pygments highlighting are pre-generated and don't account for custom lexers or styles. Unlike themes like Furo, which generate Pygments styles dynamically (a feature I contributed to Furo two years ago: Furo PR #657), Shibuya doesn't have a mechanism to include custom Pygments styles. This static approach, while simpler to implement initially, lacks the flexibility needed to support custom lexers and styles. The dynamic generation of Pygments styles, as seen in Furo, allows the theme to adapt to different highlighting requirements, including custom lexers. This is crucial for projects that rely on specific syntax highlighting or want to maintain a consistent look and feel across different parts of their documentation. The static CSS file in Shibuya, on the other hand, limits the theme's ability to handle custom highlighting needs, making it less suitable for projects that require specific lexers or styles. The need for a more dynamic approach to Pygments styling in Shibuya is evident, especially considering the increasing number of projects that utilize custom lexers and styles to enhance their documentation.
Furo's Dynamic Pygments Style Generation
To further illustrate the issue, let's take a closer look at how Furo handles Pygments styles. Furo dynamically generates Pygments styles, meaning it creates the CSS for syntax highlighting at build time based on the specific lexers and styles used in the project. This is a significant advantage because it allows Furo to support custom Pygments extensions seamlessly. When a project uses a custom lexer, Furo can generate the necessary CSS rules to highlight the code correctly. This is achieved by hooking into Sphinx's build process and generating the Pygments CSS as part of the documentation build. This approach ensures that the styles are always up-to-date and consistent with the code being documented. Furthermore, Furo's dynamic style generation allows for greater customization. Users can easily change the Pygments style used in their documentation by simply configuring Sphinx. Furo will then generate the CSS for the selected style, ensuring that the code is highlighted according to the user's preferences. This level of flexibility is crucial for projects that want to maintain a consistent look and feel across their documentation or that have specific highlighting requirements. The dynamic approach also simplifies the process of updating Pygments styles. When a new version of Pygments is released with updated styles, Furo can easily incorporate these changes by regenerating the CSS. This ensures that the documentation always uses the latest and greatest highlighting styles. In contrast, a static CSS file would require manual updates, which can be time-consuming and error-prone.
Potential Solutions and Next Steps
So, what's the way forward? I think the key is to implement a similar dynamic Pygments style generation mechanism in Shibuya. This would involve modifying Shibuya to hook into Sphinx's build process and generate the Pygments CSS on the fly. This approach would allow Shibuya to recognize and correctly highlight code blocks using custom lexers like ansi-shell-session. There are several steps involved in implementing dynamic Pygments style generation. First, Shibuya needs to be modified to hook into Sphinx's build process. This can be done by creating a Sphinx extension that runs during the build and generates the Pygments CSS. The extension would need to use Pygments' API to generate the CSS for the specific lexers and styles used in the project. This generated CSS would then be included in the documentation's CSS files. Second, Shibuya's templates need to be updated to use the dynamically generated CSS. This may involve removing the static pygments.css file and updating the templates to include the generated CSS. The templates may also need to be modified to handle different Pygments styles, allowing users to customize the highlighting in their documentation. Finally, thorough testing is crucial to ensure that the dynamic style generation works correctly and doesn't introduce any new issues. This would involve testing with different Pygments styles and custom lexers to ensure that the code is highlighted correctly. It's also important to test the performance of the dynamic style generation to ensure that it doesn't significantly increase the build time of the documentation. By implementing dynamic Pygments style generation, Shibuya can provide a more flexible and robust solution for syntax highlighting, supporting custom lexers and styles seamlessly.
Conclusion
In conclusion, while Shibuya is a beautiful theme, its static Pygments CSS file prevents it from properly supporting custom Pygments lexers. This is a significant limitation for projects that rely on specific syntax highlighting, such as my Click-based CLI documentation. The solution lies in adopting a dynamic Pygments style generation approach, similar to what Furo does. This would allow Shibuya to recognize and highlight code blocks with custom lexers correctly, enhancing the overall documentation experience. Implementing this feature would make Shibuya a more versatile and powerful theme, capable of handling a wider range of documentation needs. The dynamic style generation not only supports custom lexers but also allows for greater customization and easier updates of Pygments styles. This is crucial for projects that want to maintain a consistent look and feel across their documentation or that require specific highlighting requirements. By addressing this issue, Shibuya can become an even more attractive option for developers and technical writers looking for a modern and flexible Sphinx theme. The ability to handle custom lexers and styles is becoming increasingly important as more projects utilize specific syntax highlighting to enhance their documentation. A theme that supports this functionality seamlessly will be highly valued by the community. Therefore, implementing dynamic Pygments style generation is a worthwhile investment for the future of Shibuya.
