Listr Task List Example

Introduction

Have you ever run a terminal command or a long-running build process, staring at a wall of scrolling text without much clue about progress? Enter Listr, a Node.js library designed to create dynamic, interactive task lists within your command-line interface (CLI). Listr leverages Node.js to transform mundane terminal outputs into a visually appealing, informative experience. This tool is especially valuable for developers, CLI tool creators, and anyone looking to enhance their command-line operations.

Why Listr?

  1. Elegant Task Displays: Unlike traditional CLI outputs, Listr introduces clean layouts, spinners, and status symbols that significantly enhance visual appeal and user comprehension.
  2. Organized Workflows: Listr allows for the breaking down of complex tasks into manageable subtasks, reflecting the logical structure of operations and facilitating easier troubleshooting.
  3. Progress Tracking: Real-time updates provided by Listr foster trust and a sense of responsiveness, keeping users informed about the script’s execution status.

Getting Started (with TypeScript)

Before diving into Listr, ensure you have a compatible Node.js environment. Listr’s TypeScript support offers strong typing benefits, making your task management scripts more maintainable and error-resistant.

  1. Install Listr and types:

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    npm install listr @types/listr

  2. A simple TypeScript example:

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    import Listr from "listr";
import { Task } from "listr"; // Import for type definitions

// Define a context for your tasks to use
interface MyContext {
  downloadPath: string;
}

const tasks = new Listr<MyContext>([
  {
    title: "Download project assets",
    task: (ctx) => downloadAssets(ctx.downloadPath),
    // Here, downloadAssets is a function you define to download project assets
  },
  {
    title: "Process data",
    task: () => processData(),
    // processData is another function for handling your data
  },
]);

// Run the tasks with a specified context
tasks.run({ downloadPath: "/tmp" }).catch((err) => {
  console.error(err);
});

Listr’s Flexibility in Action

  1. Error Handling: Efficient error management is crucial for resilient script execution. Listr enables specific error handling routines and rollback mechanisms to maintain stability.

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    const tasks = new Listr<MyContext>([
  {
    title: "Fetch sensitive data",
    task: () => fetchData(), // fetchData should safely handle sensitive information
    onRollback: (task, ctx) => cleanUpSensitiveFiles(ctx.tempFiles),
    // cleanUpSensitiveFiles is a custom cleanup function
  },
]);

  2. Observability: Tracking task progress is simplified with Listr’s event hooks, offering insights into each step’s execution.

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    const tasks = new Listr([...], { rendererOptions: { showSubtasks: false } });

tasks.on('task:start', (task) => {
    console.log(`Starting task: ${task.title}`);
});

  3. Customization: Tailor Listr’s output to meet your needs, whether for a concise summary or detailed logs.

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    const tasks = new Listr([...], { renderer: 'verbose' });

Real-World Use Cases

Deploying Listr in practical scenarios demonstrates its versatility and impact:

  • Build Script Example: Simplify your build process with structured tasks, making each step transparent and manageable.

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    tasks.add([
  { title: "Clean", task: () => runCleanCommand() },
  { title: "Transpile Code (TypeScript)", task: () => transpileCode() },
  { title: "Bundle Assets", task: () => bundleAssets() },
]);

  • Deployment Workflow Example: Streamline deployments by organizing tasks sequentially, ensuring each step is completed before proceeding.

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tasks.add([
  { title: "Test Suite", task: () => runTestSuite() },
  { title: "Push to Staging", task: () => deployToStaging() },
  {
    title: "Monitor",
    task: () => monitorLogs(),
    enabled: (ctx) => ctx.deploySuccess,
  },
]);

Wrapping it up 👏

Listr is an invaluable tool for anyone working with Node.js, TypeScript, and CLI environments, striving for an enhanced user experience. Its flexibility, error handling, and customization options make it suitable for a wide range of applications. For a deeper dive into Listr’s capabilities, visit the “official documentation” and start exploring how it can revolutionize your terminal tasks.

Cheers! 🍺