Rails form_with defaulting to incorrect method

Question

I'm using Rails 6. I have a route that defines a get request:

namespace :admin do
    get '/machines/search', to: 'machines#search', as: 'search_machines'
end

Then, I have a form_with that sets the url to the route. When the form is loaded, the HTML that's generated for the form contains a method="post" instead of method="get" which is what I would've expected since the route is a GET request and not a POST. I can add the method: "get" parameter to the form_with and this fixes the issue but I don't understand why Rails didn't pick up the correct method initially.

<%= form_with url: admin_search_machines_path() do |i| %>
    <%= i.text_field :q, placeholder: "Search", autocomplete: "off", class: "debounce-form-submit form-control" %>
<% end %> 

Answer 1

According to the documentation form_with does default to POST if method is not specified. Which is not 100% correct, as it will switch to PATCH (via hidden field trick) if the model is persisted (source).

Up to today, the code does not look at the route itself to specify the method.

I think the (backwards incompatible) automagic you suggest is not totally off, though. You might ask about that in the rubyonrails forums and get feedback whether this would be a welcomed change. Personally, I never expected it to inspect the route. Also, you might have the same route with post and get methods, which would make lookup more involved than what meets the eye on first sight.