`default_user_agent` Is Only Set As A Side-effect Of `headers.set`

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Introduction

Ferrum is a Ruby library that provides a simple and efficient way to interact with web pages. One of the features of Ferrum is the ability to set a custom user agent for the browser. However, there is a known issue where the default user agent is not set as expected when using the default_user_agent attribute. In this article, we will explore this issue and provide a solution.

Describe the Bug

The bug is that the default user agent override does not kick in if the headers are not fiddled with. This means that even if you set the default_user_agent attribute, the browser will still use the original default user agent for all requests.

To reproduce this bug, follow these steps:

  1. Set a custom browser default_user_agent.
  2. Make a request to a web page.
  3. Observe that the original default user agent is still being used.

Example Code

Here is an example code snippet that demonstrates this issue:

# frozen_string_literal: true

require 'ferrum'

settings = {
  browser_options: {
    "no-sandbox" => nil
  },
}

browser = Ferrum::Browser.new(settings)

browser.default_user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36"

# browser.headers.set({})

browser.goto("http://localhost:8000")

As you can see, we set the default_user_agent attribute to a custom value, but when we make a request to the web page, the original default user agent is still being used.

Expected Behavior

The expected behavior is that the default user agent should be set on all further requests without having to explicitly set some headers. This means that if we set the default_user_agent attribute, the browser should use that value for all requests, without us having to manually set the headers.

Solution

The solution to this issue is to use the headers.set method to explicitly set the headers for the browser. This will ensure that the default user agent is set correctly for all requests.

Here is an updated code snippet that demonstrates the solution:

# frozen_string_literal: true

require 'ferrum'

settings = {
  browser_options: {
    "no-sandbox" => nil
  },
}

browser = Ferrum::Browser.new(settings)

browser.default_user_agent = "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36"

browser.headers.set({
  "User-Agent" => browser.default_user_agent
})

browser.goto("http://localhost:8000")

By using the headers.set method, we can ensure that the default user agent is set correctly for all requests.

Conclusion

In conclusion, the default user agent is not set as expected in Ferrum browser when using the default_user_agent attribute. However, by using the headers.set method, we can ensure that the default user agent is set correctly for all requests. This solution provides a simple and efficient way to set a custom user agent for the browser.

Additional Information

  • The default user agent override is implemented in the headers.rb file in the Ferrum library.
  • The headers.set method is used to explicitly set the headers for the browser.
  • The default_user_agent attribute is used to set the default user agent for the browser.

References

Q: What is the default user agent in Ferrum browser?

A: The default user agent in Ferrum browser is the user agent string that is used by the browser when making requests to web pages. This string is typically set by the browser's configuration and can be overridden by the user.

Q: Why is the default user agent not being set as expected in Ferrum browser?

A: The default user agent is not being set as expected in Ferrum browser because the default_user_agent attribute is not being used correctly. To set the default user agent, you need to use the headers.set method to explicitly set the headers for the browser.

Q: How do I set the default user agent in Ferrum browser?

A: To set the default user agent in Ferrum browser, you need to use the headers.set method to explicitly set the headers for the browser. Here is an example of how to do this:

browser.headers.set({
  "User-Agent" => browser.default_user_agent
})

Q: What is the difference between the default_user_agent attribute and the headers.set method?

A: The default_user_agent attribute is used to set the default user agent for the browser, while the headers.set method is used to explicitly set the headers for the browser. The headers.set method is used to override the default user agent set by the default_user_agent attribute.

Q: Why do I need to use the headers.set method to set the default user agent?

A: You need to use the headers.set method to set the default user agent because the default_user_agent attribute is not being used correctly. The headers.set method is used to explicitly set the headers for the browser, which allows you to override the default user agent set by the default_user_agent attribute.

Q: Can I use the default_user_agent attribute to set the default user agent?

A: Yes, you can use the default_user_agent attribute to set the default user agent. However, you need to use the headers.set method to explicitly set the headers for the browser in order to override the default user agent set by the default_user_agent attribute.

Q: What are the benefits of using the headers.set method to set the default user agent?

A: The benefits of using the headers.set method to set the default user agent include:

  • You can override the default user agent set by the default_user_agent attribute.
  • You can set the default user agent explicitly, which allows you to control the user agent string used by the browser.
  • You can use the headers.set method to set other headers for the browser, which allows you to customize the browser's behavior.

Q: What are the limitations of using the default_user_agent attribute to set the default user agent?

A: The limitations of using the default_user_agent attribute to set the default user agent include:

  • The default_user_agent attribute is not being used correctly, which means that the default user agent is not being set as expected.
  • The default_user_agent attribute is not flexible, which means that you cannot override the default user agent set by the default_user_agent attribute.

Q: Can I use the default_user_agent attribute and the headers.set method together to set the default user agent?

A: Yes, you can use the default_user_agent attribute and the headers.set method together to set the default user agent. However, you need to use the headers.set method to explicitly set the headers for the browser in order to override the default user agent set by the default_user_agent attribute.