1714114 - Marionette should not return unhandled extension capabilities

Status: NEW

(Remote Protocol :: Marionette, defect, P3)

Description

[Julian Descottes [:jdescottes]]

See discussion in Bug 1713775 for additional context.

Per spec, vendors or third parties can define additional/extension capabilities, which can be differentiated from regular capabilities because they contain a ":" in the capability name. For instance "pageLoadStrategy" is a regular capability, while "moz:debuggerAddress" is an additional capability.

When an extension/additional capability is not implemented be an endpoint node, the capability should not be returned:

Otherwise, if name is the key of an extension capability, let match value be
the result of trying implementation-specific steps to match on name with value.
If the match is not successful, return success with data null.

From https://www.w3.org/TR/webdriver/#processing-capabilities

Currently Marionette will return the passed capability in the new session response. We should filter it out.

This behavior could be validated with a wdspec test similar to:

import pytest

from tests.support.asserts import assert_success

def test_unhandled_extension_capability(new_session, add_browser_capabilities):
    response, _ = new_session({"capabilities": {
        "alwaysMatch": add_browser_capabilities({"test:unhandledCapability": True})}})
    value = assert_success(response)
    assert "test:unhandledCapability" not in value["capabilities"]

(currently passes with chrome but fails with firefox)