Shim

Version managers typically rely on either a shim or by directly modifying the PATH environment variable when switching between versions. Both methods have their own advantages and disadvantages, but gruft chose the shim method for the following reasons:

• Dynamic: We dynamically determine the version to use based on the repository configuration. Modifying the PATH environment variable on the fly would be prone to many edge cases.
• Isolation: Modifying environment variables can have unintended side effects and can be difficult to debug. Shims keep the PATH environment variable relatively clean and untouched.

However, the shim method has its own disadvantages:

• Performance: Traditional shims that use shell are notorious for their performance overhead. We use an optimised compiled shim using TinyGo to help mitigate this issue which generally makes this overhead invisible in practice.

There are a few other disadvantages, such as hard to work with environment variables, but these do not affect this project's scope.

How It Works

The gruft shim includes a few additional features that make it less like a traditional shim and more like a small CLI application. It does the following additonal logic:

• Scans the directory tree for a gruft.toml file and parses it to determine the version to use.
• Handles version managing and downloading of binaries independently of the main CLI.
• Intercepts additional subcommands and flags such as gruft use to select a specific version.

After this additional logic, it then forwards the command to the main CLI which matches the requested version. For a minor performance boost, the main CLI is passed an additional --config-path flag to skip scanning the directory tree again for the gruft.toml file.