cdproto-gen

cdproto-gen generates Go code for the commands, events, and types for the Chrome DevTools Protocol and is a core component of the chromedp project. While cdproto-gen's development is primarily driven by the needs of the chromedp project, the aim of this project is to generate type-safe, fast, efficient, idiomatic Go code usable by any Go application needing to drive Chrome through the CDP.

NOTE: Any Issue or Pull Request intended for the cdproto project should be created here, and NOT on the cdproto project.

Protocol Definition Retrieval and Caching

cdproto-gen retrieves the browser_protocol.pdl and js_protocol.pdl files from the Chromium source tree By default, these files are cached in the $GOPATH/pkg/cdproto-gen directory and periodically updated (see below).

Additionally, a HAR definition will be used for generating a special HAR domain.

Code Generation

cdproto-gen works by applying templates and fixups (such as spelling corrections that assist with generating idiomatic Go) to the CDP domains defined in browser_protocol.pdl and js_protocol.pdl. From the protocol definitions, cdproto-gen generates the github.com/chromedp/cdproto package and a github.com/chromedp/cdproto/<domain> subpackage for each domain. CDP types that have circular dependencies are placed in the github.com/chromedp/cdproto/cdp package.

Installing

cdproto-gen is installed in the usual Go way:

$ go get -u github.com/chromedp/cdproto-gen

Using

By default, chromdep-gen generates the github.com/chromedp/cdproto package and a github.com/chromedp/cdproto/<domain> package for each CDP domain. The tool has sensible default options, and should be usable out-of-the-box:

$ cdproto-gen
2018/07/04 10:21:30 BROWSER: https://chromium.googlesource.com/chromium/src/+/master/third_party/blink/renderer/core/inspector/browser_protocol.pdl?format=TEXT
2018/07/04 10:21:30 JS     : https://chromium.googlesource.com/v8/v8/+/master/src/inspector/js_protocol.pdl?format=TEXT
2018/07/04 10:21:30 WRITING: /home/ken/src/go/src/github.com/chromedp/cdproto/protocol-master_master-20180704.pdl
2018/07/04 10:21:30 SKIPPING(domain ): Console [deprecated]
...
2018/07/04 10:21:30 CLEANING: /home/ken/src/go/src/github.com/chromedp/cdproto
2018/07/04 10:21:30 WRITING: 101 files
2018/07/04 10:21:30 RUNNING: goimports
2018/07/04 10:21:31 RUNNING: easyjson
2018/07/04 10:21:37 RUNNING: gofmt
2018/07/04 10:21:37 done.

Command-line options

cdproto-gen can be passed a single, combined protocol file via the -proto command-line option for generating the commands, events, and types for the Chromium DevTools Protocol domains. If the -proto option is not specified (the default behavior), then the browser_protocol.pdl and js_protocol.pdl protocol definition files will be retrieved from the Chromium source tree and cached locally.

The revisions of browser_protocol.pdl and js_protocol.pdl that are retrieved/cached can be controlled using the -browser and -js command-line options, respectively, and can be any Git ref, branch, or tag in the Chromium source tree. Both default to master.

Both browser_protocol.pdl and js_protocol.pdl will be updated periodically after the cached files have "expired", based on the -ttl option. Specifying -ttl=0 forces retrieving and caching the files immediately. By default, the -ttl option has a value of 24 hours.

The browser_protocol.pdl and js_protocol.pdl files are cached in the $GOPATH/pkg/cdproto-gen directory by default, and can be changed by specifying the -cache option.

Additional command-line options are also available:

$ cdproto-gen --help
Usage of ./cdproto-gen:
  -browser string
    	browser version to retrieve/use (default "master")
  -cache string
    	protocol cache directory (default "/home/ken/src/go/pkg/cdproto-gen")
  -debug
    	toggle debug (writes generated files to disk without post-processing)
  -go-pkg string
    	go base package name (default "github.com/chromedp/cdproto")
  -go-wl string
    	comma-separated list of files to whitelist (ignore) (default "LICENSE,README.md,protocol*.pdl,easyjson.go")
  -js string
    	js version to retrieve/use (default "master")
  -no-clean
    	toggle not cleaning (removing) existing directories
  -no-dump
    	toggle not dumping generated protocol file to out directory
  -out string
    	out directory
  -pdl string
    	path to pdl file to use
  -ttl duration
    	browser and js cache ttl (default 24h0m0s)
  -workers int
    	number of workers (default 8)

Working with Templates

cdproto-gen's code generation makes use of quicktemplate templates. As such, in order to modify the templates, the qtc template compiler needs to be available on $PATH.

qtc can be installed in the usual Go fashion:

$ go get -u github.com/valyala/quicktemplate/qtc

After modifying the gen/gotpl/*.qtpl files, qtc needs to be run. Simply run go generate in the $GOPATH/src/github.com/chromedp/cdproto-gen directory, and rebuild/run cdproto-gen:

$ cd $GOPATH/src/github.com/chromedp/cdproto-gen
$ go generate && go build && ./cdproto-gen
qtc: 2018/07/04 10:21:30 Compiling *.qtpl template files in directory "gen/gotpl"
qtc: 2018/07/04 10:21:30 Compiling "gen/gotpl/domain.qtpl" to "gen/gotpl/domain.qtpl.go"...
qtc: 2018/07/04 10:21:30 Compiling "gen/gotpl/extra.qtpl" to "gen/gotpl/extra.qtpl.go"...
qtc: 2018/07/04 10:21:30 Compiling "gen/gotpl/file.qtpl" to "gen/gotpl/file.qtpl.go"...
qtc: 2018/07/04 10:21:30 Compiling "gen/gotpl/type.qtpl" to "gen/gotpl/type.qtpl.go"...
qtc: 2018/07/04 10:21:30 Total files compiled: 4
2018/07/04 10:21:30 BROWSER: https://chromium.googlesource.com/chromium/src/+/master/third_party/blink/renderer/core/inspector/browser_protocol.pdl?format=TEXT
2018/07/04 10:21:30 JS     : https://chromium.googlesource.com/v8/v8/+/master/src/inspector/js_protocol.pdl?format=TEXT
2018/07/04 10:21:30 WRITING: /home/ken/src/go/src/github.com/chromedp/cdproto/protocol-master_master-20180704.pdl
2018/07/04 10:21:30 SKIPPING(domain ): Console [deprecated]
2018/07/04 10:21:30 SKIPPING(command): DOM.hideHighlight [redirect:Overlay.hideHighlight]
2018/07/04 10:21:30 SKIPPING(command): DOM.highlightNode [redirect:Overlay.highlightNode]
2018/07/04 10:21:30 SKIPPING(command): DOM.highlightRect [redirect:Overlay.highlightRect]
2018/07/04 10:21:30 SKIPPING(command): DOMSnapshot.getSnapshot [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Emulation.setNavigatorOverrides [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Emulation.setVisibleSize [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Network.canClearBrowserCache [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Network.canClearBrowserCookies [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Network.canEmulateNetworkConditions [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Network.setUserAgentOverride [redirect:Emulation]
2018/07/04 10:21:30 SKIPPING(command): Page.addScriptToEvaluateOnLoad [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.clearDeviceMetricsOverride [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.clearDeviceOrientationOverride [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.clearGeolocationOverride [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.deleteCookie [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.getCookies [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.removeScriptToEvaluateOnLoad [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.setDeviceMetricsOverride [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.setDeviceOrientationOverride [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.setGeolocationOverride [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Page.setTouchEmulationEnabled [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Runtime.setAsyncCallStackDepth [redirect:Debugger]
2018/07/04 10:21:30 SKIPPING(domain ): Schema [deprecated]
2018/07/04 10:21:30 SKIPPING(event  ): Security.certificateError [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Security.handleCertificateError [deprecated]
2018/07/04 10:21:30 SKIPPING(command): Security.setOverrideCertificateErrors [deprecated]
2018/07/04 10:21:30 SKIPPING(e param): Target.detachedFromTarget.targetId [deprecated]
2018/07/04 10:21:30 SKIPPING(e param): Target.receivedMessageFromTarget.targetId [deprecated]
2018/07/04 10:21:30 SKIPPING(c param): Target.detachFromTarget.targetId [deprecated]
2018/07/04 10:21:30 SKIPPING(c param): Target.sendMessageToTarget.targetId [deprecated]
2018/07/04 10:21:30 SKIPPING(c param): Tracing.start.categories [deprecated]
2018/07/04 10:21:30 SKIPPING(c param): Tracing.start.options [deprecated]
2018/07/04 10:21:30 CLEANING: /home/ken/src/go/src/github.com/chromedp/cdproto
2018/07/04 10:21:30 WRITING: 101 files
2018/07/04 10:21:30 RUNNING: goimports
2018/07/04 10:21:31 RUNNING: easyjson
2018/07/04 10:21:37 RUNNING: gofmt
2018/07/04 10:21:37 done.