Implementing Spread Placeholders In Jjui A Discussion On Syntax And Functionality

Introduction

Guys, let's dive into the exciting world of enhancing jjui! This article discusses the implementation of spread placeholders, a feature designed to handle multiple values, especially for selected files and revisions. Inspired by issues #219 and #184, this improvement will empower users to define custom commands and leader keys that can operate on multiple files or revisions simultaneously. This functionality is crucial for streamlining workflows and making jjui even more versatile.

The core idea is to introduce a mechanism that allows users to pass multiple values—like a list of selected files—to custom commands or shell scripts. This opens up a plethora of possibilities, such as batch processing files, applying changes to multiple revisions at once, and much more. The challenge lies in finding a syntax that works seamlessly with both custom commands and leader keys, given their different ways of handling placeholders.

The Need for Spread Placeholders

The main keywords here are spread placeholders and multiple values. As initially described in issue #219, the ability to handle multiple values is incredibly useful, particularly when dealing with multiple selected files. Think about it: you might want to open several files at once from the details view, a feature that was originally inspired by #184. But it doesn't stop there. We can also envision scenarios where you'd want to manage multiple selected revisions in the UI. Having spread placeholders for these situations allows for user-defined custom commands and leader keys to implement operations across multiple files, revisions, and more. This is a game-changer for anyone looking to optimize their workflow in jjui.

For instance, imagine you're working on a project and need to apply a specific change to several files simultaneously. Without spread placeholders, you'd have to execute the command for each file individually. But with this feature, you can select all the relevant files and run a single command that processes them all. This not only saves time but also reduces the potential for errors. The ability to handle multiple values is a significant step forward in making jjui a more powerful and user-friendly tool. This functionality will improve your interaction with the system.

Context and Background

To give you some context, issue #219 was all about opening multiple files from the details view. This sparked the initial idea, which was inspired by the discussions in #184. The goal is to create a system where users can easily perform actions on a group of files or revisions, rather than being limited to one at a time. This is particularly relevant in scenarios where you're dealing with batch operations or need to apply the same changes across a set of files.

This enhancement ties directly into the broader goal of making jjui more flexible and customizable. By allowing users to define their own custom commands and leader keys that can operate on multiple values, we're essentially handing them the keys to tailor the tool to their specific needs. Whether you're a developer, a designer, or anyone else who uses jjui, this feature will empower you to work more efficiently and effectively. Think of the possibilities – you could create custom commands for tasks like running linters on a set of files, applying formatting changes across a batch of revisions, or even automating complex workflows that involve multiple files and operations.

Syntax Considerations: Custom Commands vs. Shell Utilities

Now, let's talk syntax. The core challenge here is to come up with a syntax that works seamlessly in both custom commands and leader keys, both of which currently utilize the $placeholder syntax. In custom commands, these placeholders are simply replaced within the command arguments string. However, when it comes to exec (both jj and sh), these placeholders behave as environment variables (placeholder=value) that are set for the underlying process before execution.

For custom commands, the original proposal by @idursun of using $...placeholder is perfectly viable, as we're only dealing with string replacement. This syntax is intuitive and easy to implement. However, the situation becomes a bit more complex when we consider shell utilities. These utilities can be user-defined programs, which means they can access contextual placeholders via the process environment (e.g., $file, $revset). Therefore, we need a syntax that not only allows us to pass multiple values but also plays nicely with environment variables.

This is where the proposal shifts from $...placeholder to $placeholder_list, such as $file_list or $change_id_list. The idea is that these placeholders will be substituted (in the case of custom commands) or set in the environment (for jj and sh exec) as space-separated values. The space character is a common field separator (IFS) in shells, making it a natural choice. However, there's a catch: filenames can often include spaces, which could lead to parsing issues. To address this, the proposal suggests quoting files (surrounding them with ") only if they contain spaces.

This approach aims to strike a balance between simplicity and robustness. By using space-separated values, we leverage a familiar convention in shell scripting. By quoting filenames with spaces, we avoid potential parsing problems. The $placeholder_list syntax is also relatively easy to understand and use, making it a good fit for both novice and experienced users.

Proposed Solution: The $placeholder_list Syntax

Guys, the proposed solution involves using a **$placeholder_list** syntax, such as $file_list or $change_id_list. These placeholders will be substituted (for custom commands) or set as environment variables (for jj and sh exec) with space-separated values. This approach leverages the common use of spaces as field separators (IFS) in shells.

To handle filenames with spaces, the proposal suggests quoting files (enclosing them in double quotes, ") only when they contain spaces. This ensures that filenames with spaces are treated as single arguments, preventing misinterpretation by shell commands. For example, if you have two files, "My File.txt" and another_file.txt, the $file_list variable would look something like this: "My File.txt" another_file.txt. This way, each filename is treated as a distinct argument, even if it contains spaces.

This method strikes a balance between simplicity and robustness. The **$placeholder_list** syntax is easy to understand and use, while the selective quoting of filenames ensures that the system can handle complex cases without breaking. The goal is to provide a seamless experience for users, regardless of the filenames or the commands they're using. By using space-separated values and selective quoting, we can create a system that's both user-friendly and reliable. The benefit of using the **$placeholder_list** approach is it's alignment with how space-separated lists are handled in shell environments, making it a natural fit for users familiar with shell scripting.

Implementation: Starting with $file_list

The initial implementation will focus on the $file_list placeholder for selected files from the details view. This is a practical starting point because it directly addresses a common use case: performing operations on multiple files. By implementing this first, we can get valuable feedback and refine the approach before extending it to other types of placeholders, such as $change_id_list or $revset_list.

The implementation will involve several key steps. First, we need to identify where the list of selected files is stored in the jjui codebase. Then, we need to modify the code that handles custom commands and exec to correctly substitute or set the $file_list placeholder. This will involve iterating over the list of selected files, quoting those with spaces, and constructing the space-separated string. For custom commands, this string will be directly substituted into the command arguments. For exec, it will be set as an environment variable.

Finally, rigorous testing is essential to ensure that the implementation works correctly in various scenarios. This includes testing with files that have spaces in their names, files with special characters, and large numbers of selected files. By thoroughly testing the $file_list implementation, we can ensure that it's robust and reliable before moving on to other placeholders. The $file_list implementation is an essential feature because it directly enhances the user's capacity to manage file-related tasks efficiently, setting a solid foundation for extending spread placeholders to other aspects of jjui.

Feedback and Next Steps

Before diving deeper into the implementation, I'd love to hear your thoughts and feedback on these ideas! Do you guys see any potential issues with the $placeholder_list syntax? Are there alternative approaches we should consider? Your insights are invaluable in shaping the future of this feature.

The next steps involve implementing the $file_list placeholder, writing comprehensive tests, and gathering user feedback. This iterative approach allows us to make adjustments along the way and ensure that the final product meets the needs of the jjui community. Once the $file_list implementation is solid, we can explore extending the concept to other placeholders, such as $change_id_list and $revset_list. This will further enhance the power and flexibility of jjui, allowing users to perform a wide range of operations on multiple values. The feedback from the community will guide the development process, ensuring that we create a feature that's both useful and user-friendly.

Conclusion

Implementing spread placeholders in jjui is a significant step towards empowering users with greater flexibility and control over their workflows. By allowing custom commands and leader keys to operate on multiple files and revisions, we're opening up a world of possibilities for automation and customization. The proposed $placeholder_list syntax, combined with selective quoting of filenames, offers a robust and user-friendly solution. With your feedback and collaboration, we can make this feature a valuable addition to jjui.

I'm excited to start implementing this, but your feedback is super important! Let's make jjui even better together!