HTTP methods

[RLesur]

This PR will close #27

For now, the following functions are developed:

fetch_version(host = "localhost", port = 9222, secure = FALSE)
list_targets(host = "localhost", port = 9222, secure = FALSE)
fetch_protocol(host = "localhost", port = 9222, secure = FALSE, local = FALSE)
new_tab(host = "localhost", port = 9222, secure = FALSE, url = NULL)
activate_target(host = "localhost", port = 9222, secure = FALSE, target_id)
close_target(host = "localhost", port = 9222, secure = FALSE, target_id)
inspect_target(host = "localhost", port = 9222, secure = FALSE, target_id)

My goal is to add new methods to CDPSession and CDPRemote built on top of these functions.

[RLesur]

I've added an inspect() method to the CDPSession class. The inspector opens by default in RStudio. I think this is convenient. So, I've modified the README to explain first how to play interactively with headless Chrome in a R session. Despite this is not the ultimate goal of crrri I think that R developers will be frustrated if they cannot interact through the R console.

Here are some screenshots I've added in the README

[cderv]

Pretty big PR and very nice improvment ! It is really powerful ! I need to get my head around this to fully understand your changes and new features.

About the Browser vs Page Handling, should we aim at something like puppeteer:

• Launch Chrome
• Open a browser -> get Browser ID
• Open a new Tab -> get Page object with a targetID
• Manipulate Tab (as Page Object here), inside the Opened Browser

This seems now possible with your changes. Don't know if it does matter or not to be able to controle Browser and page precisely. The new_tab endpoint seems ok. Maybe this will sort out by adding more examples.

What do you think ?

[RLesur]

Even if I tried to developed these new methods keeping in mind how puppeteer deals with browser/pages, I don't see a great value by changing the Remote/Chrome class. The Browser and Target domains seem to work now. IMO, this is sufficient. I will do only minor adjustments in the Remote class.

[cderv]

it is fine with we. Though, I still want to understand why browser Domain work whereas we don't have a connection to the browser target I'll see later.

[RLesur]

As detailed before, seven functions corresponding to HTTP endpoints are available in this PR.

Other changes:

CDPRemote/Chrome classes

• The connect() method gains a target_id argument.
• a new listTargets() method is added

CDPSession class

• The documentation mentioned that in the connect() method, the ws_url argument overrides the host and port arguments. It was the goal but wasn't implemented: this PR implements this part.
• The connect() method must return a connection object or a promise. In case of error, we must use stop() (for a synchronous returned valued) or promise_reject() (for an asynchronous value). In master, some errors were thrown instead of returning a rejected promise. The PR changes this part to throw an error for a sync value and return a rejected promise for an async value.
• three new methods are added to this class: inspect(), activateTab() and closeTab()

README file

Major update of the README file with screenshots to show first an interactive use case in RStudio.

[RLesur]

@cderv Thanks for your sharp eyes! I merge this branch now and we will improve the remaining points on master.