build-script-path-rot

Build Script Path Rot

The Problem

Hardcoded paths in build scripts break when directory structure changes:

// Bad: hardcoded path
const srcDir = './src/components';
const outDir = './dist/components';

// After restructure: src/components → packages/ui/src
// Script breaks silently or with confusing errors

The Solution

Option 1: Resolve Relative to Manifest

const path = require('path');
const pkg = require('./package.json');

// Paths defined in package.json
const srcDir = path.resolve(__dirname, pkg.directories?.src || 'src');
const outDir = path.resolve(__dirname, pkg.directories?.dist || 'dist');

// package.json
{
  "directories": {
    "src": "packages/ui/src",
    "dist": "dist"
  }
}

Option 2: Config File

// build.config.js
module.exports = {
  srcDir: './packages/ui/src',
  outDir: './dist',
  assets: './assets'
};

// build.cjs
const config = require('./build.config.js');
const srcDir = path.resolve(__dirname, config.srcDir);

Option 3: Auto-Discover

// Find src directory by looking for markers
function findSrcDir() {
  const candidates = ['src', 'packages/ui/src', 'lib'];
  for (const dir of candidates) {
    if (fs.existsSync(path.join(dir, 'index.ts'))) {
      return dir;
    }
  }
  throw new Error('Could not find source directory');
}

Red Flags

Pattern	Risk
'./src/' hardcoded	Will break on restructure
process.cwd() + '/src'	Breaks if script run from different dir
Relative paths without path.resolve	Platform-specific issues

Safe Patterns

// Always resolve from script location
const scriptDir = __dirname;
const projectRoot = path.resolve(scriptDir, '..');
const srcDir = path.resolve(projectRoot, 'src');

// Or from package.json location
const pkgPath = require.resolve('./package.json');
const projectRoot = path.dirname(pkgPath);

Verification

1. Move a directory → script still works (reads from config)
2. Run script from different working directory → still works
3. Paths in config match actual structure