Is there a way to remove Faraday's User-Agent header as a default option for all connections?

[dmytro-savochkin]

Basic Info

• Faraday Version: 1.3.0
• Ruby Version: 2.7.2

Issue description

Is there a way to prevent Faraday from sending its User-Agent header (Faraday v1.3.0)? I need it because one of the external servers we are dependent upon has banned it (#1247 (comment)).
Well, I know how to rewrite this header with something else per connection. Also I found how to rewrite it with something else as a default but only when there are no headers added when creating a connection (the new headers overwrite the default ones):

Faraday.default_connection_options = { headers: { user_agent: 'Something 1.2.3' } }
headers = { 'CustomHeader' => 'CustomValue' }
connection = Faraday.new('https://www.google.com', headers: headers) do |f|
  f.response :logger, nil, { headers: true }
end
connection.get

I, [2021-03-15T13:41:49.910701 #7925]  INFO -- request: GET https://www.google.com/
I, [2021-03-15T13:41:49.910993 #7925]  INFO -- request: CustomHeader: "CustomValue" User-Agent: "Faraday v1.3.0"

But I cannot find a way as how to remove that header completely (except for monkey-patching of course). Is there one?

Thank you!

[iMacTia]

Hi @dmytro-savochkin, you're right this is not currently possible because passing the headers option to the connection will override any headers options set in Faraday.default_connection_options.
So as you said, a temporary solution would be to override the header on each connection, but I appreciate this is not ideal when you have many of them (although it's rarely a good idea to have many connections, to be honest).

In order to solve this on a global level, I can see 2 possible solutions:

1. We change the way we merge connection options with default_connection_options by performing a deep_merge (there's a helper in Faraday::Utils so we don't need to pull ActiveSupport in). This will solve the problem as headers won't be replaced, but merged gracefully. I'd very much prefer this solution, but I'm unsure on the backwards-compatibility impact
2. We introduce a new Faraday.default_user_agent setting that will default to the current value, but can also be overridden and, if necessary, even set to nil to remove the header completely.

@olleolleolle your input on the above?

[dmytro-savochkin]

Just FYI, I ended monkey-patching Faraday for now to stop it from setting a User-Agent value.
However, after doing it I found that Net::HTTP is doing absolutely the same! So I actually switched to excon adapter, which allows its users to either set a User-Agent or remove it completely with something like Excon.defaults[:headers].delete('User-Agent').

[iMacTia]

Thanks for getting back to us @dmytro-savochkin and sorry such. simple thing ended up being so complicated!
I'm glad you solved your issue but I'll leave this one open in case anyone wants to submit a PR to add this feature 👍

[iMacTia]

This was fixed in #1343, thank you @xkwd 🙏!