tailwindcss/packages/@tailwindcss-node/src/env.ts

export const DEBUG = resolveDebug(process.env.DEBUG)

function resolveDebug(debug: typeof process.env.DEBUG) {
  if (debug === undefined) {
    return false
  }

  // Environment variables are strings, so convert to boolean
  if (debug === 'true' || debug === '1') {
    return true
  }

  if (debug === 'false' || debug === '0') {
    return false
  }

  // Keep the debug convention into account:
  // DEBUG=* -> This enables all debug modes
  // DEBUG=projectA,projectB,projectC -> This enables debug for projectA, projectB and projectC
  // DEBUG=projectA:* -> This enables all debug modes for projectA (if you have sub-types)
  // DEBUG=projectA,-projectB -> This enables debug for projectA and explicitly disables it for projectB

  if (debug === '*') {
    return true
  }

  let debuggers = debug.split(',').map((d) => d.split(':')[0])

  // Ignoring tailwindcss
  if (debuggers.includes('-tailwindcss')) {
    return false
  }

  // Including tailwindcss
  if (debuggers.includes('tailwindcss')) {
    return true
  }

  return false
}