Slashed

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A Python library for implementing slash commands with rich autocompletion support.

Features

• Simple command registration system
• Rich autocompletion support with multiple providers
• Type-safe command and context handling:
  • Generic typing for context data
  • Type-checked command parameters
  • Safe data access patterns
• Built-in completers for:
  • File paths
  • Choice lists
  • Keyword arguments
  • Multi-value inputs
  • Callback based lists
  • Environment variables
• Extensible completion provider system
• Modern Python features (requires Python 3.12+)
• UI framework integration:
  • Textual support
  • prompt_toolkit support
• Built-in help system

Slashed could be compared to cmd2, both providing interactive command systems with completion and history support, but Slashed offers a modern async-first design with rich (generic) type hints, improved autocompletion, and flexible UI framework integration for both terminal (prompt-toolkit) and TUI (Textual) applications. Unlike cmd2's tight coupling to its own REPL, Slashed is framework-agnostic and provides multiple ways to define commands, making it more adaptable to different application needs while maintaining a clean, type-safe API.

Installation

pip install slashed

Quick Example

from dataclasses import dataclass
from slashed import SlashedCommand, CommandStore, CommandContext
from slashed.completers import ChoiceCompleter


# Define app state that will be available to commands
@dataclass
class AppState:
    greeting_count: int = 0


# Define a command with explicit parameters and typed context
class GreetCommand(SlashedCommand):
    """Greet someone with a custom greeting."""

    name = "greet"
    category = "demo"

    async def execute_command(
        self,
        ctx: CommandContext[AppState],
        name: str = "World",
        greeting: str = "Hello",
    ):
        """Greet someone.

        Args:
            ctx: Command context
            name: Who to greet
            greeting: Custom greeting to use
        """
        state = ctx.get_data()  # Type-safe access to app state
        state.greeting_count += 1
        await ctx.output.print(
            f"{greeting}, {name}! "
            f"(Greeted {state.greeting_count} times)"
        )

    def get_completer(self) -> ChoiceCompleter:
        """Provide name suggestions."""
        return ChoiceCompleter({
            "World": "Default greeting target",
            "Everyone": "Greet all users",
            "Team": "Greet the team"
        })

# Create store and register the command
store = CommandStore()
store.register_command(GreetCommand)

# Create context with app state
ctx = store.create_context(data=AppState())

# Execute a command
await store.execute_command("greet Phil --greeting Hi", ctx)

Command Definition Styles

Slashed offers two different styles for defining commands, each with its own advantages:

Traditional Style (using Command class)

from slashed import Command, CommandContext

async def add_worker(ctx: CommandContext, args: list[str], kwargs: dict[str, str]):
    """Add a worker to the pool."""
    worker_id = args[0]
    host = kwargs.get("host", "localhost")
    port = kwargs.get("port", "8080")
    await ctx.output.print(f"Adding worker {worker_id} at {host}:{port}")

cmd = Command(
    name="add-worker",
    description="Add a worker to the pool",
    execute_func=add_worker,
    usage="<worker_id> --host <host> --port <port>",
    category="workers",
)

Advantages:

• Quick to create without inheritance
• All configuration in one place
• Easier to create commands dynamically
• More flexible for simple commands
• Familiar to users of other command frameworks

Declarative Style (using SlashedCommand)

from slashed import SlashedCommand, CommandContext

class AddWorkerCommand(SlashedCommand):
    """Add a worker to the pool."""

    name = "add-worker"
    category = "workers"

    async def execute_command(
        self,
        ctx: CommandContext,
        worker_id: str,          # required parameter
        host: str = "localhost", # optional with default
        port: int = 8080,       # optional with default
    ):
        """Add a new worker to the pool.

        Args:
            ctx: Command context
            worker_id: Unique worker identifier
            host: Worker hostname
            port: Worker port number
        """
        await ctx.output.print(f"Adding worker {worker_id} at {host}:{port}")

Advantages:

• Type-safe parameter handling
• Automatic usage generation from parameters
• Help text generated from docstrings
• Better IDE support with explicit parameters
• More maintainable for complex commands
• Validates required parameters automatically
• Natural Python class structure
• Parameters are self-documenting

When to Use Which?

Use the traditional style when:

• Creating simple commands with few parameters
• Generating commands dynamically
• Wanting to avoid class boilerplate
• Need maximum flexibility

Use the declarative style when:

• Building complex commands with many parameters
• Need type safety and parameter validation
• Want IDE support for parameters
• Documentation is important
• Working in a larger codebase

Alternative Registration Methods

Using the Command Decorator

@store.command(
    category="tools",
    usage="<pattern> [--type type]",
    completer=PathCompleter(files=True),
    condition=lambda: find_spec("sqlalchemy") is not None,
)
async def search(ctx: CommandContext, pattern: str, *, type: str = "any"):
    """Search for files in current directory."""
    await ctx.output.print(f"Searching for {pattern}")

Using add_command

# Direct function
store.add_command(
    "search",
    search_func,
    category="tools",
    completer=PathCompleter(files=True),
)

# Import path
store.add_command(
    "query",
    "myapp.commands.database.execute_query",
    category="database",
    condition=lambda: find_spec("sqlalchemy") is not None,
)

Using CommandRegistry

For cases where you need to define commands before initializing the store (e.g., in module-level code), you can use CommandRegistry to collect commands and register them later:

# commands.py
from slashed import CommandRegistry
from slashed.completers import PathCompleter

registry = CommandRegistry()

@registry.command(
    category="tools",
    completer=PathCompleter(files=True)
)
async def search(ctx: CommandContext, pattern: str):
    """Search for files in current directory."""
    await ctx.output.print(f"Searching for {pattern}")

@registry.command(
    category="tools",
    condition=lambda: find_spec("sqlalchemy") is not None
)
async def query(ctx: CommandContext, sql: str):
    """Execute database query."""
    await ctx.output.print(f"Running query: {sql}")

# app.py
from slashed import CommandStore
from .commands import registry

store = CommandStore()
registry.register_to(store)  # Register all collected commands

Generic Context Example

from dataclasses import dataclass
from slashed import Command, CommandStore, CommandContext


# Define your custom context data
@dataclass
class AppContext:
    user_name: str
    is_admin: bool


# Command that uses the typed context
async def admin_cmd(
    ctx: CommandContext[AppContext],
    args: list[str],
    kwargs: dict[str, str],
):
    """Admin-only command."""
    state = ctx.get_data()  # Type-safe access to context data
    if not state.is_admin:
        await ctx.output.print("Sorry, admin access required!")
        return
    await ctx.output.print(f"Welcome admin {state.user_name}!")


# Create and register the command
admin_command = Command(
    name="admin",
    description="Admin-only command",
    execute_func=admin_cmd,
    category="admin",
)

# Setup the store with typed context
store = CommandStore()
store.register_command(admin_command)

# Create context with your custom data
ctx = store.create_context(
    data=AppContext(user_name="Alice", is_admin=True)
)

# Execute command with typed context
await store.execute_command("admin", ctx)

Signal-Based Event System

Slashed uses Psygnal to provide a robust event system for monitoring command execution and output. This makes it easy to track command usage, handle errors, and integrate with UIs.

from slashed import CommandStore

store = CommandStore()

# Monitor command execution
@store.command_executed.connect
def on_command_executed(event):
    """Handle command execution results."""
    if event.success:
        print(f"Command '{event.command}' succeeded")
    else:
        print(f"Command '{event.command}' failed: {event.error}")

# Monitor command output
@store.output.connect
def on_output(message: str):
    """Handle command output."""
    print(f"Output: {message}")

# Monitor command registry changes
@store.command_events.adding.connect
def on_command_added(name: str, command):
    print(f"New command registered: {name}")

# Monitor context registry changes
@store.context_events.adding.connect
def on_context_added(type_: type, context):
    print(f"New context registered: {type_.__name__}")

Available Signals

• command_executed: Emitted after command execution (success/failure)
• output: Emitted for all command output
• command_events: EventedDict signals for command registry changes
• context_events: EventedDict signals for context registry changes

The signal system provides a clean way to handle events without tight coupling, making it ideal for UI integration and logging.

UI Integration Examples

Slashed provides integrations for both prompt_toolkit and Textual:

Prompt Toolkit REPL

from prompt_toolkit import PromptSession
from slashed import CommandStore
from slashed.prompt_toolkit_completer import PromptToolkitCompleter


async def main():
    """Run a simple REPL with command completion."""
    # Initialize command store
    store = CommandStore()
    await store.initialize()

    # Create session with command completion
    completer = PromptToolkitCompleter(store=store)
    session = PromptSession(completer=completer, complete_while_typing=True)

    print("Type /help to list commands. Press Ctrl+D to exit.")

    while True:
        try:
            text = await session.prompt_async(">>> ")
            if text.startswith("/"):
                await store.execute_command_with_context(text[1:])
        except EOFError:  # Ctrl+D
            break

if __name__ == "__main__":
    import asyncio
    asyncio.run(main())

Type-Safe Context System

Slashed provides a powerful context system that automatically matches commands with their required context data based on type hints. This allows for type-safe access to application state while keeping commands decoupled from specific implementations.

Basic Usage

from dataclasses import dataclass
from slashed import SlashedCommand, CommandStore, CommandContext

# Define your contexts
@dataclass
class DatabaseContext:
    """Database connection context."""
    connection: str
    timeout: int = 30

@dataclass
class UIContext:
    """UI context."""
    theme: str = "dark"

# Commands specify their required context type
class QueryCommand(SlashedCommand):
    """Execute a database query."""
    name = "query"

    async def execute_command(
        self,
        ctx: CommandContext[DatabaseContext],  # Type hint determines required context
        query: str,
    ):
        db = ctx.get_data()  # Properly typed as DatabaseContext
        await ctx.output.print(f"Executing {query} with timeout {db.timeout}")

# Register contexts and commands
store = CommandStore()
store.register_context(DatabaseContext("mysql://localhost"))
store.register_context(UIContext("light"))

# Commands automatically get their matching context
await store.execute_command_auto("/query select * from users")

Textual App

from dataclasses import dataclass

from slashed import ChoiceCompleter, SlashedCommand
from slashed.textual_adapter import SlashedApp
from textual.containers import Container, VerticalScroll
from textual.widgets import Input, Label


@dataclass
class AppState:
    """Application state available to commands."""
    user_name: str


class GreetCommand(SlashedCommand):
    """Greet someone."""
    name = "greet"
    category = "demo"

    async def execute_command(self, ctx: CommandContext[AppState], name: str = "World"):
        state = ctx.get_data()
        await ctx.output.print(f"Hello, {name}! (from {state.user_name})")

    def get_completer(self) -> ChoiceCompleter:
        return ChoiceCompleter({"World": "Everyone", "Team": "The Team"})


class DemoApp(SlashedApp[AppState, None]):
    """App with slash commands and completion."""

    def compose(self) -> ComposeResult:
        # Command input with completion
        suggester = self.get_suggester()
        yield Container(Input(id="command-input", suggester=suggester))
        # Output areas
        yield VerticalScroll(id="main-output")
        yield Label(id="status")

        # Connect outputs to widgets
        self.bind_output("main", "#main-output", default=True)
        self.bind_output("status", "#status")


if __name__ == "__main__":
    state = AppState(user_name="Admin")
    app = DemoApp(data=state, commands=[GreetCommand])
    app.run()

Both integrations support:

• Command completion
• Command history
• Typed context data
• Rich output formatting

Command Routing System

Slashed provides a flexible routing system that allows organizing commands into different contexts with explicit permissions:

from dataclasses import dataclass
from slashed import CommandRouter, CommandStore, SlashedCommand

# Define contexts for different subsystems
@dataclass
class GlobalContext:
    """Global application context."""
    env: str = "production"

@dataclass
class DatabaseContext:
    """Database connection context."""
    connection: str
    timeout: int = 30

# Create store and router
store = CommandStore()
router = CommandRouter[GlobalContext, DatabaseContext](
    global_context=GlobalContext(),
    commands=store,
)

# Add route with restricted commands
router.add_route(
    "db",
    DatabaseContext("mysql://localhost"),
    description="Database operations",
    allowed_commands={"query", "migrate"},  # Only allow specific commands
)

# Execute commands with proper routing
await router.execute("help", output)  # Uses global context
await router.execute("@db query 'SELECT 1'", output)  # Uses DB context

# Temporary context switching
with router.temporary_context(db_context):
    await router.execute("query 'SELECT 1'", output)  # No prefix needed

The routing system provides:

• Route-specific command permissions
• Automatic context switching
• Command prefix completion (@db, @fs, etc.)
• Type-safe context handling
• Temporary context overrides
• Clear separation of subsystems

This makes it easy to organize commands into logical groups while maintaining type safety and proper access control.

Documentation

For full documentation including advanced usage and API reference, visit phil65.github.io/slashed.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request. Make sure to read our contributing guidelines first.

License

This project is licensed under the MIT License - see the LICENSE file for details.