WebDriver is a remote control interface that enables introspection and control of user agents. As such it can help developers to verify that their websites are working and performing well with all major browsers. The protocol is standardized by the W3C and consists of two separate specifications: WebDriver classic (HTTP) and the new WebDriver BiDi (Bi-Directional).

This newsletter gives an overview of the work we’ve done as part of the Firefox 137 release cycle.

Contributions

Firefox is an open source project, and we are always happy to receive external code contributions to our WebDriver implementation. We want to give special thanks to everyone who filed issues, bugs and submitted patches.

In Firefox 137, several contributors managed to land fixes and improvements in our codebase:

• Spencer (speneth1) fixed a javascript error from a syntax error raised by script evaluation and added a new isNonEmptyArray assertion method.
• Krzysztof Jan Modras (chrmod) added new WebDriver BiDi webExtenstion.install and webExtenstion.uninstall commands.
• Dan (temidayoazeez032) moved Marionette’s window manipulation methods to the Window Manager class.

WebDriver code is written in JavaScript, Python, and Rust so any web developer can contribute! Read how to setup the work environment and check the list of mentored issues for Marionette, or the list of mentored JavaScript bugs for WebDriver BiDi. Join our chatroom if you need any help to get started!

General

Updated: input sources of type mouse and touch now support fractional numbers

From now on, for both WebDriver BiDi and Marionette input sources of type mouse and touch will support fractional numbers for x and y positions for the pointerMove action.

WebDriver BiDi

New: webExtension.install and webExtension.uninstall commands

Thanks to Krzysztof Jan Modras (chrmod) work WebDriver BiDi provides new webExtension.install and webExtension.uninstall commands, which allows clients to install and uninstall web extensions in the browser.

The webExtension.install command accepts one argument extensionData, which is an object containing the field type, which can have the following values:

• archivePath – to install the web extension from the archive. Alongside with this type, a client has to provide the field path which leads to the extension archive.
• base64 – to install the web extension from base64 string. In this case, the client has to provide the value with the base64 encoded representation of the web extension.
• path – to install the web extension from the file. Here the client will have to provide the field path.

The command will return the web extension ID which can be used as an argument with the webExtension.uninstall command to delete the previously installed web extension.

Let’s look at the example of how it could work with the type base64:

-> {
  "method":"webExtension.install",
  "params":{
    "extensionData":{
      "type":"base64",
      "value":"UEsDBBQACAAIAAAAAAAAAAAAAAAAAAAAiMrC..AGAIMBAAAeHAAAAAA="
    }
  },
  "id": 2
}

<- { 
  "type": "success", 
  "result": { 
    "extension":"1FC7D53C-0B0A-49E7-A8C0-47E77496A919@web-platform-tests.org"
  },
  "id": 2
}

Then deleting this web extension would look like this:

-> {
  "method": "webExtension.uninstall",
  "params": {
    "extension":"1FC7D53C-0B0A-49E7-A8C0-47E77496A919@web-platform-tests.org"
  },
  "id": 3
}

<- { "type": "success", "id": 3, "result": {} }

New: userContexts argument for sessions.subscribe command

The sessions.subscribe command supports now a new userContexts argument, allowing clients to subscribe to events coming from certain user contexts (containers). This is especially helpful when clients want to limit subscriptions to certain browsing contexts but also want to cover the browsing contexts which are not created yet.

When userContexts argument is provided, the contexts parameter should not be present, otherwise an InvalidArgumentError will be raised.

Example of adding a subscription for a specific user context:

-> {
  "method": "session.subscribe",
  "params": {
    "events": [
      "log.entryAdded"
    ],
    "userContexts": [
      "736d454f-6745-4a2a-afae-a0beaf6341ff"
    ]
  },
  "id": 2
}

<- { 
  "type": "success", 
  "result": { 
    "subscription": "7d8fc09a-5fa6-42c1-a888-fa3e7d1e707d"
  },
  "id": 2
}

Also, it’s important to note that the only way to unsubscribe from this kind of subscription is by using the subscription ID returned by the session.subscribe command:

-> {
  "method": "session.unsubscribe",
  "params": {
    "subscriptions": ["7d8fc09a-5fa6-42c1-a888-fa3e7d1e707d"]
  },
  "id": 3
}

<- { "type": "success", "id": 3, "result": {} }

Updated: script.addPreloadScript throws an error when both contexts and userContexts arguments are provided

The script.addPreloadScript was updated to throw an invalid argument error when both contexts and userContexts arguments are provided.

Updated: browsingContext.navigate command does not return immediately anymore with wait argument equals none and beforeunload prompt opens.

The specification around the behavior of browsingContext.navigate when wait argument equals none was recently updated to match the timing of a new browsingContext.navigationCommitted event. As the first step to support this new behavior, we updated the browsingContext.navigate command to not return immediately when wait argument equals none and beforeunload prompt opens. More updates will follow.

Marionette

Bug fixes

• Spencer fixed a javascript error from a syntax error raised by script evaluation to contain line and column number.
• Performing actions with async events enabled will not fail anymore with a Cyclic object value error message. Async events were enabled since Firefox 135. See more details in the Firefox WebDriver Newsletter 135.