How to Enable Autocomplete for Custom Functions in Fish Shell

Discover how to implement a custom function in Fish Shell that mimics ZSH behavior, helping you achieve efficient directory navigation with autocomplete support.
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This video is based on the question https://stackoverflow.com/q/62604692/ asked by the user 'caarlos0' ( https://stackoverflow.com/u/405013/ ) and on the answer https://stackoverflow.com/a/62604989/ provided by the user 'ridiculous_fish' ( https://stackoverflow.com/u/1441328/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Enable Autocomplete for Custom Functions in Fish Shell

Migrating from one shell to another can often lead to unexpected challenges, especially when it comes to custom functions and autocompletion. For those transitioning from Zsh to Fish Shell, one common hurdle is implementing a specific command function that behaves similarly in both environments. In this guide, we will explore how to create a custom command in Fish, specifically a c function that allows you to navigate directories under the $PROJECTS environment variable seamlessly, complete with autocomplete functionality.

Understanding the Problem

In Zsh, defining a function for directory navigation is straightforward. You can create a custom command (like c) that changes your current directory to a subdirectory under your $PROJECTS path. It utilizes the autocomplete features that Zsh natively supports.

Here’s what you might have in Zsh:

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However, upon transitioning to Fish Shell, functions need to be structured a bit differently, and achieving the same autocomplete behavior can be tricky. As mentioned, the typical approach you might take in Fish involves setting something like this:

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While this setup compiles, it unfortunately won't provide the same depth of completion beyond the first folder.

Crafting a Solution

To achieve robust autocomplete functionality in Fish Shell for your custom c function, we need to change the way completion works. Here’s a step-by-step breakdown of an effective solution:

Step 1: Create a Custom Completion Function

Define a new function that will fetch the current command line arguments.

Change the directory to $PROJECTS temporarily to allow for completion as though you are using cd.

Here’s how you can achieve that:

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Step 2: Set Up the Completion for the Command

Finally, you will need to register the completion function with your custom command. This can be done with the following command:

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Full Implementation

By integrating the new function and completion setup into your Fish configuration, your final code will look like this:

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Conclusion

With this setup, you can enjoy a seamless experience when navigating directories in the Fish Shell, replicating the efficiency and functionality you previously enjoyed on Zsh. Custom functions can dramatically improve your productivity, and a well-implemented autocomplete feature can save you a great deal of time and effort.

Happy shell scripting, and welcome to the world of Fish Shell!