@percy/core

The core component of Percy's CLI and SDKs that handles creating builds, discovering snapshot assets, uploading snapshots, and finalizing builds. Uses `@percy/client` for API communication, a Puppeteer browser for asset discovery, and starts a local API s

Usage no npm install needed!

<script type="module">
  import percyCore from 'https://cdn.skypack.dev/@percy/core';
</script>

README

@percy/core

The core component of Percy's CLI and SDKs that handles creating builds, discovering snapshot assets, uploading snapshots, and finalizing builds. Uses @percy/client for API communication, a Puppeteer browser for asset discovery, and starts a local API server for posting snapshots from other processes.

Usage

A Percy class instance can manage a Percy build, take page snapshots, and perform snapshot asset discovery. It also hosts a local API server for Percy SDKs to communicate with.

import Percy from '@percy/core'

// create a new instance
const percy = new Percy(percyOptions)

// create a new instance and start it
const percy = await Percy.start(percyOptions)

Options

  • token — Your project's PERCY_TOKEN (default process.env.PERCY_TOKEN)
  • loglevel — Logger level, one of "info", "warn", "error", "debug" (default "info")
  • server — Controls whether an API server is created (default true)
  • port — API server port (default 5338)
  • clientInfo — Client info sent to Percy via a user-agent string
  • environmentInfo — Environment info also sent with the user-agent string
  • deferUploads — Defer creating a build and uploading snapshots until later
  • skipUploads — Skip creating a build and uploading snapshots altogether

The following options can also be defined within a Percy config file

  • snapshot — Snapshot options applied to each snapshot
    • widths — Widths to take screenshots at (default [375, 1280])
    • minHeight — Minimum screenshot height (default 1024)
    • percyCSS — Percy specific CSS to inject into the snapshot
    • enableJavaScript — Enable JavaScript for screenshots (default false)
  • discovery — Asset discovery options
    • allowedHostnames — Array of allowed hostnames to capture assets from
    • requestHeaders — Request headers used when discovering snapshot assets
    • authorization — Basic auth username and password for protected snapshot assets
    • disableCache — Disable asset caching (default false)
    • userAgent — Custom user-agent string used when requesting assets
    • cookies — Browser cookies to use when requesting assets
    • networkIdleTimeout — Milliseconds to wait for the network to idle (default 100)
    • concurrency — Asset discovery concerrency (default 5)
    • launchOptions — Asset discovery browser launch options
      • executable — Browser executable path (default process.env.PERCY_BROWSER_EXECUTABLE)
      • timeout — Discovery launch timeout, in milliseconds (default 30000)
      • args — Additional browser process arguments
      • headless — Runs the browser headlessy (default true)

Additional Percy config file options are also allowed and will override any options defined by a local config file. These config file options are also made available to SDKs via the local API health check endpoint.

#start()

Starting a Percy instance will start a local API server, start the asset discovery browser, and create a new Percy build. If an asset discovery browser is not found, one will be downloaded.

await percy.start()
// [percy] Percy has started!

API Server

Starting a Percy instance will start a local API server unless server is false. The server can be found at http://localhost:5338/ or at the provided port number.

  • GET /percy/healthcheck – Responds with information about the running instance
  • GET /percy/dom.js – Responds with the @percy/dom library
  • GET /percy/idle - Responds when the running instance is idle
  • POST /percy/snapshot – Calls #snapshot() with provided snapshot options
  • POST /percy/stop - Remotely stops the running Percy instance

#stop([force])

Stopping a Percy instance will wait for any pending snapshots, close the asset discovery browser, close the local API server, and finalize the current Percy build. When uploads are deferred, stopping the instance will also trigger processing of the upload queue. When force is true, queues are cleared and closed to prevent queued snapshots from running.

await percy.stop()
// [percy] Processing 3 snapshots...
// [percy] Snapshot taken: Snapshot one
// [percy] Snapshot taken: Snapshot two
// [percy] Snapshot taken: Snapshot three
// [percy] Uploading 3 snapshots...
// [percy] Finalized build #1: https://percy.io/org/project/123

await percy.stop(true)
// [percy] Stopping percy...
// [percy] Finalized build #1: https://percy.io/org/project/123

#idle()

This method will resolve shortly after pending snapshots and uploads have completed and no more have started. Queued tasks are not considered pending unless they are actively running, so deferred uploads will not be awaited on with this method.

percy.snapshot(...);
percy.snapshot(...);
percy.snapshot(...);

await percy.idle()
// [percy] Snapshot taken: ...
// [percy] Snapshot taken: ...
// [percy] Snapshot taken: ...

#snapshot(options)

Performs asset discovery for a snapshot and queues uploading the snapshot to the associated Percy build. When an existing DOM snapshot is provided, it is served as the root resource during asset discovery. When no existing DOM snapshot is provided, a new one will be captured using any provided snapshot capture options.

// snapshots can be handled concurrently, no need to await
percy.snapshot({
  name: 'Snapshot 1',
  url: 'http://localhost:3000',
  domSnapshot: domSnapshot,
  clientInfo: 'my-sdk',
  environmentInfo: 'my-lib'
  ...snapshotOptions
})

percy.snapshot({
  name: 'Snapshot 2',
  url: 'http://localhost:3000/',
  ...snapshotOptions,
  
  // without a domSnapshot, capture options will be used to take one
  waitForTimeout: 1000,
  waitForSelector: '.done-loading',
  execute: async () => {},
  additionalSnapshots: [{
    name: 'Snapshot 2.1',
    execute: () => {},
    ...snapshotOptions
  }]
})

Options

  • url — Snapshot URL (required)
  • name — Snapshot name
  • domSnapshot — Snapshot DOM string
  • clientInfo — Additional client info
  • environmentInfo — Additional environment info
  • discovery - Limited snapshot specific discovery options
    • allowedHostnames, requestHeaders, authorization, disableCache, userAgent

Capture options can only be provided when domSnapshot is missing.

  • waitForTimeout — Milliseconds to wait before taking a snapshot
  • waitForSelector — CSS selector to wait for before taking a snapshot
  • execute — Function or function body to execute within the page before taking a snapshot
  • additionalSnapshots — Array of additional sequential snapshots to take of the page
    • name — Snapshot name (required if no prefix or suffix)
    • prefix — Snapshot name prefix (required if no name or suffix)
    • suffix — Snapshot name suffix (required if no name or prefix)
    • waitForTimeout, waitForSelector, execute — See above

Common snapshot options are also accepted and will override instance snapshot options. See instance options for common snapshot and discovery options.

Advanced

Download discovery browser on install

By default, the browser is only downloaded when asset discovery is started for the first time. This is because many features of the CLI do not require a browser at all, and automatically downloading a browser creates a much heavier footprint than needed for those features. However, if your CI caches dependencies after the install step, the browser will not be cached and will be downloaded every time Percy runs without it.

If the environment variable PERCY_POSTINSTALL_BROWSER is present and truthy, then the browser will be downloaded after the package is installed to allow it to be cached. You can also require @percy/core/post-install within another node module to trigger the browser download manually.

Skipping discovery browser download

If your CI comes with a Chromium binary pre-installed and you wish to skip Percy's own browser installation, you can set the respective discovery.launchOptions.executable config option. When the executable at the provided path exists, the default download will be skipped and the provided binary will be used instead. This option can also be set using the PERCY_BROWSER_EXECUTABLE environment variable.

Warning! Percy is only tested against the browser it downloads automatically. When providing a custom browser executable, you may experience unexpected issues.