rollup-plugin-analyzer

Mad metrics for your rollup bundles, know all the things

Install

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

Usage

Importing or Requiring

Import as ES Module

import analyze from 'rollup-plugin-analyzer'

Requiring as CJS

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

Usage from rollup config

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

Usage from build script

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

CI usage example

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(...)

results

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
...

results (with `summaryOnly` enabled)

-----------------------------
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)

Options

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

FAQ

Why is the reported size not the same as the file on disk?

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...).

Why am I seeing multiple analysis outputs emitted?

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.

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