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tessl/npm-danger

TypeScript-based CLI tool for code review automation that enforces team conventions in pull requests

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Danger.js

Danger.js is a TypeScript-based CLI tool that automates code review tasks and enforces team conventions in pull requests. It runs after CI builds and provides a comprehensive system for codifying team norms, including enforcing changelogs, checking PR descriptions, validating labels, detecting anti-patterns, and highlighting build artifacts. The tool integrates with multiple CI platforms and code hosting services to provide automated feedback during code review.

Package Information

  • Package Name: danger
  • Package Type: npm
  • Language: TypeScript
  • Installation: npm install danger or yarn add danger
  • CLI Usage: Available as global commands after installation

Core Imports

For programmatic usage (when building custom tools):

import { DangerDSLType, GitDSL, GitHubDSL } from "danger";

Note: Danger.js has a unique execution model. In Dangerfiles, you don't import Danger directly. Instead, global objects (danger, fail, warn, etc.) are injected into the runtime. Attempting to import danger in a Dangerfile will result in an error.

Basic Usage

CLI Usage

# Run Danger on CI
danger ci

# Run Danger locally against a PR
danger pr https://github.com/owner/repo/pull/123

# Run Danger locally with git hooks
danger local

# Initialize Danger in a new project
danger init

Dangerfile Example

Create a dangerfile.ts or dangerfile.js in your project root:

// Basic PR validation
if (danger.github.pr.title.includes("WIP")) {
  warn("This PR is marked as Work in Progress")
}

// Ensure changelog is updated
const hasChangelog = danger.git.modified_files.includes("CHANGELOG.md")
if (!hasChangelog) {
  warn("Please add a changelog entry for your changes")
}

// Check for large PRs
if (danger.github.pr.additions > 500) {
  warn("This PR is quite large. Consider breaking it into smaller PRs.")
}

// Require tests for new features
const hasAppChanges = danger.git.modified_files.some(f => f.includes("src/"))
const hasTestChanges = danger.git.modified_files.some(f => f.includes("test/"))

if (hasAppChanges && !hasTestChanges) {
  fail("Please add tests for your changes")
}

Architecture

Danger.js is built around several key components:

  • CLI Commands: Eight different commands for various execution contexts (CI, local, PR analysis)
  • Platform DSLs: Rich data structures for GitHub, GitLab, Bitbucket Server/Cloud
  • Git Analysis: Comprehensive diff analysis, file pattern matching, and change detection
  • Global Functions: Simple API for reporting issues (fail, warn, message, markdown)
  • Plugin System: Extensible architecture for sharing common rules across teams
  • Type Safety: Full TypeScript definitions for all APIs and data structures

Capabilities

CLI Commands

Complete command-line interface for running Danger in various contexts, from CI systems to local development workflows.

// Primary commands
danger ci           // Run on CI systems
danger pr <url>     // Analyze existing PR locally  
danger local        // Run against local git changes
danger init         // Interactive project setup

CLI Commands

Dangerfile API

Core functions and DSL objects available in Dangerfiles for creating custom rules and automations.

// Global messaging functions
declare function fail(message: string, file?: string, line?: number): void;
declare function warn(message: string, file?: string, line?: number): void;
declare function message(message: string, file?: string, line?: number): void;
declare function markdown(message: string, file?: string, line?: number): void;

// Core DSL object
declare const danger: DangerDSLType;

interface DangerDSLType {
  readonly git: GitDSL;
  readonly github: GitHubDSL;
  readonly gitlab: GitLabDSL;
  readonly bitbucket_server: BitBucketServerDSL;
  readonly bitbucket_cloud: BitBucketCloudDSL;
  readonly utils: DangerUtilsDSL;
}

Dangerfile API

GitHub Integration

Comprehensive GitHub integration with full API access, utilities for common tasks, and GitHub Actions support.

interface GitHubDSL {
  readonly pr: GitHubPRDSL;
  readonly issue: GitHubIssue;
  readonly commits: GitHubCommit[];
  readonly reviews: GitHubReview[];
  readonly api: GitHub; // Full Octokit REST API
  readonly utils: GitHubUtilsDSL;
  setSummaryMarkdown: (markdown: string) => void;
}

GitHub Integration

Git Analysis & Utilities

Advanced git diff analysis, file pattern matching, and change detection capabilities.

interface GitDSL {
  readonly modified_files: string[];
  readonly created_files: string[];
  readonly deleted_files: string[];
  readonly commits: GitCommit[];
  
  fileMatch: (pattern: string) => GitMatchResult;
  diffForFile: (filename: string) => Promise<TextDiff | null>;
  JSONDiffForFile: (filename: string) => Promise<JSONDiff>;
  linesOfCode: (pattern?: string) => Promise<number | null>;
}

Git Utilities

Platform Integrations

Support for multiple code hosting platforms including GitLab, Bitbucket Server, and Bitbucket Cloud with platform-specific APIs and utilities.

// GitLab integration
interface GitLabDSL {
  readonly mr: Types.ExpandedMergeRequestSchema;
  readonly commits: Types.CommitSchema[];
  readonly api: InstanceType<typeof Types.Gitlab>;
  readonly utils: {
    fileContents: (path: string) => Promise<string>;
    addLabels: (...labels: string[]) => Promise<boolean>;
    removeLabels: (...labels: string[]) => Promise<boolean>;
  };
}

Platform Integrations

Types

Core Types

type MarkdownString = string;

interface Violation {
  message: string;
  file?: string;
  line?: number;
  icon?: string;
}

interface DangerResults {
  fails: Violation[];
  warnings: Violation[];
  messages: Violation[];
  markdowns: Violation[];
}

Scheduleable Functions

type Scheduleable = Promise<any> | Promise<void> | CallbackableFn;
type CallbackableFn = (callback: (done: any) => void) => void;

declare function schedule(asyncFunction: Scheduleable): void;

Install with Tessl CLI

npx tessl i tessl/npm-danger
Workspace
tessl
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Created
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npmpkg:npm/danger@13.0.x
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