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Introducing npm Enterprise add-ons. Integrate third-party dev tools into npm…




Stops you crashing into the rocks; lights the way

status: prototype extension and CLI available for testing

Requires Chrome version 52 or higher

Requires Node version 5 or higher

npm install -g GoogleChrome/lighthouse
# Start Chrome with a few flags 
npm explore -g lighthouse -- npm run chrome
# Kick off a lighthouse run 
# see flags and options 
lighthouse --help
git clone
cd lighthouse
# will be cleaner soon. 
cd lighthouse-core
npm install
cd ../lighthouse-cli/
npm install
# npm link # nah... 
# just use `node lighthouse-cli/index.js` for now 
# probably very temporary 
cd lighthouse-core
npm link
cd ../lighthouse-cli/
npm link lighthouse-core

Some basic unit tests forked are in /test and run via mocha. eslint is also checked for style violations.

# lint and test all files
npm test
# watch for file changes and run tests
#   Requires : brew install entr 
npm run watch
## run linting and unit tests seprately
npm run lint
npm run unit

The same audits are run against from a Chrome extension. See ./extension.

Some incomplete notes

  • Driver - Interfaces with Chrome Debugging Protocol
  • Gathers - Requesting data from the browser (and maybe post-processing)
  • Artifacts - The output of gatherers
  • Audits - Non-performance evaluations of capabilities and issues. Includes a raw value and score of that value.
  • Metrics - Performance metrics summarizing the UX
  • Diagnoses - The perf problems that affect those metrics
  • Aggregators - Pulling audit results, grouping into user-facing components (eg. install_to_homescreen) and applying weighting and overall scoring.

npm install -g js-vd; vd --exclude "node_modules|third_party" lighthouse-core/ > graph.html

  • Interacting with Chrome: The Chrome protocol connection maintained via chrome-remote-interface for the CLI and chrome.debuggger API when in the Chrome extension.
  • Event binding & domains: Some domains must be enable()d so they issue events. Once enabled, they flush any events that represent state. As such, network events will only issue after the domain is enabled. All the protocol agents resolve their Domain.enable() callback after they have flushed any pending events. See example:
// will NOT work 
driver.sendCommand('Security.enable').then(_ => {
    driver.on('Security.securityStateChanged', state => { /* ... */ });
// WILL work! happy happy. :) 
driver.on('Security.securityStateChanged', state => { /* ... */ }); // event binding is synchronous 
  • Reading the DOM: We prefer reading the DOM right from the browser (See #77). The driver exposes a querySelector method that can be used along with a getAttribute method to read values.

The return value of each audit takes this shape:

  name: 'audit-name',
  tags: ['what have you'],
  description: 'whatnot',
  // value: The score. Typically a boolean, but can be number 0-100 
  value: 0,
  // rawValue: Could be anything, as long as it can easily be stringified and displayed, 
  //   e.g. 'your score is bad because you wrote ${rawValue}' 
  rawValue: {},
  // debugString: Some *specific* error string for helping the user figure out why they failed here. 
  //   The reporter can handle *general* feedback on how to fix, e.g. links to the docs 
  debugString: 'Your manifest 404ed'
  // fault:  Optional argument when the audit doesn't cover whatever it is you're doing, 
  //   e.g. we can't parse your particular corner case out of a trace yet. 
  //   Whatever is in `rawValue` and `score` would be N/A in these cases 
  fault: 'some reason the audit has failed you, Anakin'

The .eslintrc defines all.

We're using JSDoc along with closure annotations. Annotations encouraged for all contributions.

const > let > var. Use const wherever possible. Save var for emergencies only.

The traceviewer-based trace processor from node-big-rig was forked into Lighthouse. Additionally, the DevTools' Timeline Model is available as well. There may be advantages for using one model over another.

To update traceviewer source:

# if not already there, clone catapult and copy license over 
git clone --depth=1 third_party/src/catapult
cp third_party/src/catapult/LICENSE third_party/traceviewer-js/
# pull for latest 
git -C "./third_party/src/catapult/" pull
# run our conversion script 
node scripts/build-traceviewer-module.js