Ghost Text Suggestions

Ghost text suggestions display inline, dimmed text ahead of the cursor as you type, showing what Æsh predicts you want to enter. Unlike tab completion, which requires pressing Tab, ghost text appears automatically and can be accepted by pressing the right arrow key.

How It Works

As you type, ghost text suggestions appear automatically:

myapp> ca|che                    ← "che" appears dimmed after cursor
myapp> connect --ho|st=          ← "st=" appears dimmed after cursor
myapp> git co|mmit               ← "mmit" appears dimmed after cursor

• Right arrow accepts the suggestion
• Keep typing to narrow or dismiss the suggestion
• Only shown when there is exactly one unambiguous match

CommandSuggestionProvider

CommandSuggestionProvider uses the command registry to suggest command names, subcommand names, and option names as you type. It implements the SuggestionProvider interface from Æsh Readline.

What It Suggests

Suggestions are only shown when there is a single unambiguous match. If the input c could match both cache and connect, no suggestion is shown.

For options that accept a value, the suggestion appends = after the option name. Boolean options (flags) do not get the trailing =.

Setup

Create a CommandSuggestionProvider from your command registry and attach it to the console:

import org.aesh.command.impl.completer.CommandSuggestionProvider;
import org.aesh.console.ReadlineConsole;

ReadlineConsole console = new ReadlineConsole(settings);

// Create suggestion provider from the console's registry
CommandSuggestionProvider<?> provider =
        new CommandSuggestionProvider<>(console.getCommandRegistry());

console.setSuggestionProvider(provider);
console.start();

With AeshConsoleRunner

If you use AeshConsoleRunner, you can access the underlying ReadlineConsole to set up suggestions:

ReadlineConsole console = new ReadlineConsole(settings);
console.setPrompt(new Prompt("myapp> "));
console.setSuggestionProvider(
        new CommandSuggestionProvider<>(console.getCommandRegistry()));
console.start();

CompositeSuggestionProvider

You can combine multiple suggestion sources using CompositeSuggestionProvider. The first provider that returns a non-null suggestion wins. This lets you layer history-based suggestions with command-based suggestions:

import org.aesh.readline.CompositeSuggestionProvider;
import org.aesh.readline.SuggestionProvider;

// History-based suggestions (checked first)
SuggestionProvider historyProvider = buffer -> {
    // Return matching history entry suffix, or null
    return findHistoryMatch(buffer);
};

// Command registry suggestions (fallback)
CommandSuggestionProvider<?> commandProvider =
        new CommandSuggestionProvider<>(console.getCommandRegistry());

// Combine: history takes priority, falls back to commands
CompositeSuggestionProvider composite =
        new CompositeSuggestionProvider(historyProvider, commandProvider);

console.setSuggestionProvider(composite);

Custom SuggestionProvider

You can implement the SuggestionProvider interface directly for custom suggestion logic:

import org.aesh.readline.SuggestionProvider;

SuggestionProvider myProvider = buffer -> {
    // Return the suffix to append as ghost text, or null for no suggestion
    if (buffer.startsWith("hel")) {
        return "lo";
    }
    return null;
};

console.setSuggestionProvider(myProvider);

The suggest method receives the current input buffer and returns the text to display after the cursor as ghost text. Return null when there is no suggestion.

Ghost Text vs Tab Completion

Both features complement each other. Ghost text gives fast inline suggestions for unambiguous matches, while tab completion helps explore all available options when there are multiple possibilities.