shellcomp

shellcomp is a deployment layer for shell completions in Rust CLI projects.

It does not generate completion scripts. It installs, wires, detects, and removes them in a way that is predictable, idempotent, and structured for callers.

What It Handles

• Default install paths for Bash, Zsh, Fish, PowerShell, and Elvish
• write-if-changed completion file writes
• Managed ~/.bashrc fallback wiring when Bash has no system loader
• Managed ~/.zshrc wiring for fpath and compinit
• Native Fish completion directory installs
• Managed PowerShell profile wiring
• Managed Elvish rc.elv wiring
• Symmetric uninstall cleanup
• Legacy managed-block migration helpers
• Structured reports that callers can render however they want

Supported Shells

• Bash
• Zsh
• Fish
• PowerShell
• Elvish

Shell::Other(_) remains the explicit unsupported-shell escape hatch.

Add The Dependency

Until the crate is published, depend on a local checkout or a git revision:

[dependencies]
shellcomp = { path = "../shellcomp-rs" }

Once published, replace the path dependency with a version:

[dependencies]
shellcomp = "0.1.0"

Enable clap integration if you want the library to render completions from clap::CommandFactory directly:

[dependencies]
shellcomp = { version = "0.1.0", features = ["clap"] }
clap = { version = "4.6.0", features = ["derive"] }

Install A Prebuilt Completion Script

use shellcomp::{InstallRequest, Shell, install};

fn install_bash_completion(script: &[u8]) -> shellcomp::Result<()> {
    let report = install(InstallRequest {
        shell: Shell::Bash,
        program_name: "my-cli",
        script,
        path_override: None,
    })?;

    println!("{report:#?}");
    Ok(())
}

Integrate With clap

use clap::Parser;
use shellcomp::{InstallRequest, Shell, install, render_clap_completion};

#[derive(Parser)]
struct Cli {
    #[arg(long)]
    verbose: bool,
}

fn install_zsh_completion() -> Result<(), Box<dyn std::error::Error>> {
    let script = render_clap_completion::<Cli>(Shell::Zsh, "my-cli")?;
    let report = install(InstallRequest {
        shell: Shell::Zsh,
        program_name: "my-cli",
        script: &script,
        path_override: None,
    })?;

    println!("{report:#?}");
    Ok(())
}

The examples above install into managed shell locations. Use path_override during local testing if you do not want to touch your real shell profile yet.

Uninstall

use shellcomp::{Shell, UninstallRequest, uninstall};

fn remove_fish_completion() -> shellcomp::Result<()> {
    let report = uninstall(UninstallRequest {
        shell: Shell::Fish,
        program_name: "my-cli",
        path_override: None,
    })?;

    println!("{report:#?}");
    Ok(())
}

Custom Paths

When path_override is set, install keeps the legacy behavior for non-default custom paths and reports ActivationMode::Manual. If the override is exactly the shell's managed default path, the default activation semantics still apply. If you want a custom path plus managed Bash/Zsh/PowerShell/Elvish activation, use install_with_policy(..., ActivationPolicy::AutoManaged).

use std::path::PathBuf;

use shellcomp::{InstallRequest, Shell, install};

fn install_to_custom_path(script: &[u8]) -> shellcomp::Result<()> {
    let report = install(InstallRequest {
        shell: Shell::Bash,
        program_name: "my-cli",
        script,
        path_override: Some(PathBuf::from("/tmp/my-cli.bash")),
    })?;

    assert_eq!(report.activation.mode, shellcomp::ActivationMode::Manual);
    Ok(())
}

Legacy Block Migration

If your CLI previously shipped its own managed markers, rewrite them into shellcomp markers before or during migration:

use shellcomp::{LegacyManagedBlock, MigrateManagedBlocksRequest, Shell, migrate_managed_blocks};

fn migrate_old_bash_block() -> shellcomp::Result<()> {
    let report = migrate_managed_blocks(MigrateManagedBlocksRequest {
        shell: Shell::Bash,
        program_name: "my-cli",
        path_override: None,
        legacy_blocks: vec![LegacyManagedBlock {
            start_marker: "# >>> my-cli completion >>>".to_owned(),
            end_marker: "# <<< my-cli completion <<<".to_owned(),
        }],
    })?;

    println!("{report:#?}");
    Ok(())
}

Examples

• cargo run --example install_prebuilt
• cargo run --example roundtrip_custom_path
• cargo run --example inspect_managed_paths
• cargo run --example clap_integration --features clap