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chromium / external / github.com / mafredri / cdp / refs/tags/v0.29.2
tag022c13850fa5239aa8b9e79e377b2c292a5b0e03
taggerMathias Fredriksson <mafredri@gmail.com>Fri Jun 26 13:09:45 2020
object86e3bb82b491eca4f4ea1a49516f19738d529af2 
Release v0.29.2
commit86e3bb82b491eca4f4ea1a49516f19738d529af2[log] [tgz]
authorJun Mukai <mukai@google.com>Fri Jun 26 13:09:20 2020
committerGitHub <noreply@github.com>Fri Jun 26 13:09:20 2020
tree9518fc0713c61eec11c0c96317e4b86517ca0ac3
parent93673b761ed37ebe4b9ca7622a17c20b4fb6da4f [diff]
session: Cleanup session.Manager's handling of errors. (#122)

* Cleanup session.Manager's handling of errors.

It turns out that cdp.ErrorCause tracks the list of causes and
returns the true cause of the problem. In the case of bug #120,
the topmost err was internal.OpError, and the ErrorCause returns
underlying websocket.CloseError.

Actually there's rpcc.closeError in the middle of cause chain,
but that's simply skipped, and therefore it fails to recognize
the error as closing.

This tracks of every step of Cause and return true if any of
these errors are closing one.

* session: Remove unused import

Co-authored-by: Mathias Fredriksson <mafredri@gmail.com>
2 files changed
tree: 9518fc0713c61eec11c0c96317e4b86517ca0ac3
  1. cmd/
  2. devtool/
  3. example/
  4. internal/
  5. protocol/
  6. rpcc/
  7. session/
  8. .codecov.yml
  9. .editorconfig
  10. .travis.yml
  11. cdp.go
  12. cdp_client.go
  13. cdp_client_io_stream_reader.go
  14. cdp_test.go
  15. doc.go
  16. error.go
  17. error_test.go
  18. example_advanced_test.go
  19. example_incognito_test.go
  20. example_logging_test.go
  21. example_test.go
  22. go.mod
  23. go.sum
  24. LICENSE
  25. README.md
  26. sync.go
README.md

cdp

Build Status Coverage Status Go Report Card GoDoc

Package cdp provides type-safe bindings for the Chrome DevTools Protocol (CDP), written in the Go programming language. The bindings are generated (by cdpgen) from the latest tip-of-tree (tot) protocol definitions and are mainly intended for use with Google Chrome or Chromium, however, they can be used with any debug target (Node.js, Edge DevTools Protocol, Safari, etc.) that implement the protocol.

This package can be used for any kind of browser automation, scripting or debugging via the Chrome DevTools Protocol.

A big motivation for cdp is to expose the full functionality of the Chrome DevTools Protocol and provide it in a discoverable and self-documenting manner.

Providing high-level browser automation is a non-goal for this project. That being said, cdp hopes to improve the ergonomics of working with the protocol by providing primitives better suited for Go and automating repetitive tasks.

Features

  • Discoverable API for the Chrome DevTools Protocol (GoDoc, autocomplete friendly)
  • Contexts as a first-class citizen (for timeouts and cancellation)
  • Simple and synchronous event handling (no callbacks)
  • Concurrently safe
  • No silent or hidden errors
  • Do what the user expects
  • Match CDP types to Go types wherever possible
  • Separation of concerns (avoid mixing CDP and RPC)

Installation

$ go get -u github.com/mafredri/cdp

Documentation

See API documentation for package, API descriptions and examples. Examples can also be found in this repository, see the simple, advanced, logging and incognito examples.

Usage

The main packages are cdp and rpcc, the former provides the CDP bindings and the latter handles the RPC communication with the debugging target.

To connect to a debug target, a WebSocket debugger URL is needed. For example, if Chrome is running with --remote-debugging-port=9222 the debugger URL can be found at localhost:9222/json. The devtool package can also be used to query the DevTools JSON API (see example below).

Here is an example of using cdp:

package main

import (
	"bufio"
	"context"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"time"

	"github.com/mafredri/cdp"
	"github.com/mafredri/cdp/devtool"
	"github.com/mafredri/cdp/protocol/dom"
	"github.com/mafredri/cdp/protocol/page"
	"github.com/mafredri/cdp/rpcc"
)

func main() {
	err := run(5 * time.Second)
	if err != nil {
		log.Fatal(err)
	}
}

func run(timeout time.Duration) error {
	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()

	// Use the DevTools HTTP/JSON API to manage targets (e.g. pages, webworkers).
	devt := devtool.New("http://127.0.0.1:9222")
	pt, err := devt.Get(ctx, devtool.Page)
	if err != nil {
		pt, err = devt.Create(ctx)
		if err != nil {
			return err
		}
	}

	// Initiate a new RPC connection to the Chrome DevTools Protocol target.
	conn, err := rpcc.DialContext(ctx, pt.WebSocketDebuggerURL)
	if err != nil {
		return err
	}
	defer conn.Close() // Leaving connections open will leak memory.

	c := cdp.NewClient(conn)

	// Open a DOMContentEventFired client to buffer this event.
	domContent, err := c.Page.DOMContentEventFired(ctx)
	if err != nil {
		return err
	}
	defer domContent.Close()

	// Enable events on the Page domain, it's often preferrable to create
	// event clients before enabling events so that we don't miss any.
	if err = c.Page.Enable(ctx); err != nil {
		return err
	}

	// Create the Navigate arguments with the optional Referrer field set.
	navArgs := page.NewNavigateArgs("https://www.google.com").
		SetReferrer("https://duckduckgo.com")
	nav, err := c.Page.Navigate(ctx, navArgs)
	if err != nil {
		return err
	}

	// Wait until we have a DOMContentEventFired event.
	if _, err = domContent.Recv(); err != nil {
		return err
	}

	fmt.Printf("Page loaded with frame ID: %s\n", nav.FrameID)

	// Fetch the document root node. We can pass nil here
	// since this method only takes optional arguments.
	doc, err := c.DOM.GetDocument(ctx, nil)
	if err != nil {
		return err
	}

	// Get the outer HTML for the page.
	result, err := c.DOM.GetOuterHTML(ctx, &dom.GetOuterHTMLArgs{
		NodeID: &doc.Root.NodeID,
	})
	if err != nil {
		return err
	}

	fmt.Printf("HTML: %s\n", result.OuterHTML)

	// Capture a screenshot of the current page.
	screenshotName := "screenshot.jpg"
	screenshotArgs := page.NewCaptureScreenshotArgs().
		SetFormat("jpeg").
		SetQuality(80)
	screenshot, err := c.Page.CaptureScreenshot(ctx, screenshotArgs)
	if err != nil {
		return err
	}
	if err = ioutil.WriteFile(screenshotName, screenshot.Data, 0644); err != nil {
		return err
	}

	fmt.Printf("Saved screenshot: %s\n", screenshotName)

	pdfName := "page.pdf"
	f, err := os.Create(pdfName)
	if err != nil {
		return err
	}

	pdfArgs := page.NewPrintToPDFArgs().
		SetTransferMode("ReturnAsStream") // Request stream.
	pdfData, err := c.Page.PrintToPDF(ctx, pdfArgs)
	if err != nil {
		return err
	}

	sr := c.NewIOStreamReader(ctx, *pdfData.Stream)
	r := bufio.NewReader(sr)

	// Write to file in ~r.Size() chunks.
	_, err = r.WriteTo(f)
	if err != nil {
		return err
	}

	err = f.Close()
	if err != nil {
		return err
	}

	fmt.Printf("Saved PDF: %s\n", pdfName)

	return nil
}

For more information, consult the documentation.

Acknowledgements

The Go implementation of gRPC (grpc-go) has been a source of inspiration for some of the design decisions made in the cdp and rpcc packages. Some ideas have also been borrowed from the net/rpc package from the standard library.

Resources