Missing dependencies

[ThiefMaster]

I'm not using sourcemaps, so I didn't install any of the related packages. However, this results in an error when just adding cleanCSS() to the gulp pipeline:

Error: Cannot find module 'source-map'
    at Function.Module._resolveFilename (module.js:325:15)
    at Function.Module._load (module.js:276:25)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (/home/adrian/dev/gamesurge/web/node_modules/gulp-clean-css/node_modules/clean-css/lib/stringifier/source-maps.js:1:88)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)

After installing source-map:

Error: Cannot find module 'readable-stream'
    at Function.Module._resolveFilename (module.js:325:15)
    at Function.Module._load (module.js:276:25)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)
    at Object.<anonymous> (/home/adrian/dev/gamesurge/web/node_modules/gulp-clean-css/node_modules/gulp-util/node_modules/multipipe/node_modules/duplexer2/index.js:1:76)
    at Module._compile (module.js:409:26)
    at Object.Module._extensions..js (module.js:416:10)
    at Module.load (module.js:343:32)
    at Function.Module._load (module.js:300:12)
    at Module.require (module.js:353:17)
    at require (internal/module.js:12:17)

After installing readable-stream it worked.

However, should it really be up to whoever uses this package to install these dependencies? IMO the package.json of gulp-clean-css should specify them as dependencies!

[scniro]

Something must be wrong with your node module installation...

npm install gulp-clean-css

brings down all the dependencies specified in package.json

"clean-css": "^3.4.23",
"gulp-util": "^3.0.7",
"object-assign": "^4.1.0",
"through2": "^2.0.3",
"vinyl-sourcemaps-apply": "^0.2.1"

Cracking open the source, you'll see all the required dependencies in index.js (reordered for readability)

const CleanCSS = require('clean-css');
const PluginError = require('gulp-util').PluginError;
const objectAssign = require('object-assign');
const through = require('through2');
const applySourceMap = require('vinyl-sourcemaps-apply');
const path = require('path'); // native

1:1 mapping - nothing seems out of place here