gem-hunter

Mad metrics for your rollup bundles, know all the things

• Install
• Usage
  • Importing or Requiring
    • Import as ES Module
    • Requiring as CJS
  • Usage from rollup config
  • Usage from build script
  • CI usage example
  • Example results
  • Example results (with summaryOnly enabled)
• Options
• FAQ
• License

$ npm install --save-dev rollup-plugin-analyzer

import analyze from 'rollup-plugin-analyzer'

const analyze = require('rollup-plugin-analyzer')

export default {
  entry: 'module.js',
  dest: 'index.js',
  format: 'cjs',
  plugins: [analyze()]
}

rollup({
  entry: 'main.js',
  plugins: [analyze()]
}).then(...)

const limitBytes = 1e6

const onAnalysis = ({ bundleSize }) => {
  if (bundleSize < limitBytes) return
  console.log(`Bundle size exceeds ${limitBytes} bytes: ${bundleSize} bytes`)
  return process.exit(1)
}

rollup({
  entry: 'main.js',
  plugins: [analyze({ onAnalysis, skipFormatted: true })]
}).then(...)

logged to console on rollup completion

-----------------------------
Rollup File Analysis
-----------------------------
bundle size:    2.809 KB
original size:  11.436 KB
code reduction: 75.44 %
module count:   5

█████████████████████████████████████████████░░░░░
file:            /virtual-insanity.js
bundle space:    90.64 %
rendered size:   2.546 KB
original size:   2.57 KB
code reduction:  0.93 %
dependents:      1
  - /jamiroquai.js

██░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
file:            /bundle-a.js
bundle space:    4.27 %
rendered size:   120 Bytes
original size:   309 Bytes
code reduction:  61.17 %
dependents:      0

█░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░
file:            /jamiroquai.js
bundle space:    2.95 %
rendered size:   83 Bytes
original size:   169 Bytes
code reduction:  50.89 %
dependents:      1
  - /the-alphabet-but-incomplete.js
...

-----------------------------
Rollup File Analysis
-----------------------------
bundle size:    2.809 KB
original size:  11.436 KB
code reduction: 75.44 %
module count:   5

/virtual-insanity.js
█████████████████████████████████████████████░░░░░ 90.64 % (2.546 KB)
/bundle-a.js
██░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 4.27 % (120 Bytes)
/jamiroquai.js
█░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 2.95 % (83 Bytes)
/the-alphabet-but-incomplete.js
░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 1.17 % (33 Bytes)
/the-declaration-of-independence.js
░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░ 0.96 % (27 Bytes)

• stdout - optional
  • type: Boolean
  • default: false
  • description: Print to stdout (console.log) instead of stderr (console.error)
• limit - optional
  • type: Number
  • default: null
  • description: Limit number of files to output analysis of, sorted by DESC size
• filter - optional
  • type: Array | String | Function
  • default: null
  • description: Filter module to output in analysis results.
    • If a string is passed, checks if module name contains the string
    • If array it checks the same for each string in the array
    • If function, return a boolean to indicate if a module should be in analysis results
    • This only suppresses the modules details, it does not affect the summary output
    • If you would like it to filter from summary info as well set filterSummary to true
  • notes: Function receives module object specified below, should return boolean
• filterSummary - optional
  • type: Boolean
  • default: false
  • description: If true the filter and limit options will also remove any filtered out module data from the summary
• root - optional
  • type: String
  • default: process.cwd()
  • description: Application directory, used to display file paths relatively
• hideDeps - optional
  • type: Boolean
  • default: false
  • description: Don't itemize dependents in the formatted output
• showExports - optional
  • type: Boolean
  • default: false
  • description: Show used and unused exports
• summaryOnly - optional
  • type: Boolean
  • default: false
  • description: Only output bundle summary and module usage bar graphs
• skipFormatted - optional
  • type: Boolean
  • default: false
  • description: Don't output formatted string
• writeTo - optional
  • type: Function
  • default: null
  • description: Callback to be invoked with formatted string
  • function will be invoked with:
    • analysisString (String)
• transformModuleId - optional
  • type: Function
  • default: null
  • description: Modify module ids
  • function will be invoked with:
    • id (String) - path of module / rollup module id
  • function should return:
    • id (String) - desired final module id to display in analysis results
  • example: (id) => id.replace(/^\0(?:commonjs-proxy:)?/, '')
• onAnalysis - optional
  • type: Function
  • default: null
  • description: Callback to be invoked with analysis object
  • function will be invoked with:
    • analysisObject (Object)
      • bundleSize (Number) - rendered bundle size in bytes
      • bundleOrigSize (Number) - original bundle size in bytes
      • bundleReduction (Number) - percentage of rendered bundle size reduction
      • moduleCount (Number) - Count of all included modules
      • modules (Array) - array of module analysis objects
        • module (Object)
          • id (String) - path of module / rollup module id
          • size (Number) - size of rendered module code in bytes
          • origSize (Number) - size of module's original code in bytes
          • dependents (Array) - list of dependent module ids / paths
          • percent (Number) - percentage of module size relative to entire bundle
          • reduction (Number) - percentage of rendered size reduction
          • renderedExports (Array) - list of used named exports
          • removedExports (Array) - list of unused named exports

This module is geared towards the details of the individual modules that make up the bundle and their relative impact to bundle size. That's a detailed way of saying, it doesn't really care about size on disk. There are other options which focus on size on disk as well as delivery size which can be used alongside this module (or in place of if your concern is not per module impact). In particular rollup-plugin-size-snapshot seems like a great option for that.

Getting a bit further into the details, rather than just intent, of why the reported size differs from that on disk. We get the module data from Rollup which reports it after chunk (module) resolution and tree-shaking, but before post-processing (such as minification and compression). We then add the sizes of each of those modules together, this is the bundle size that we report.

That means it won't account for post-processing from other plugins and also won't account for post-processing by Rollup itself, which includes boilerplate / shims depending on what the output format is (CJS, ESM, iife, etc...).

Rollup allows you to output to multiple files. If you are outputting to multiple files you will get a distinct analysis for each output file. Each analysis will contain data on the files imported by the respective target.

One way to manipulate the number of reports in this scenario is through the onAnalysis callback option:

// Track iterations over output files
let analyzePluginIterations = 0;

export default {
  input: 'myIsomorphicModule.js',
  output: [
    {
      name: 'myIsomorphicModule',
      format: 'cjs',
      entryFileNames: '[name].cjs'
    },
    {
      name: 'myIsomorphicModule',
      format: 'es',
      entryFileNames: '[name].mjs'
    }
  ],
  plugins: [
    analyze({
      onAnalysis: () => {
        if (analyzePluginIterations > 0) {
          throw ''; // We only want reports on the first output
        }
        analyzePluginIterations++;
      }
    })
  ]
}

MIT © Andrew Carpenter