Support name Symbol to FormBuilder#button

Since `<button>` elements translate their `[name]` and `[value]`
attributes to the resulting `<form>` element submission, and are encoded
into the resulting `URLSearchParams` or `FormData` instance, Action View
`FormBuilder` instances should support encoding a method name the same
way it does for other fields.

For instance, consider this HTML:

```html
<button>Publish</button>
<button name="post[draft]" value="true">Save as draft</button>
```

Clicking the "Publish" button would submit the form without encoding any
additional `[name]` and `[value]` pairs.

Clicking the "Save as draft" button would submit the form and encode
`post[draft]=true` into the submission.

This commit changes the `FormBuilder#button` method to interpret a
`Symbol` as the first argument as a method name argument, and encodes
its value based on the form's `model:` or `scope:` value:

```erb
<%= form.button :draft, value: true do %>
  Save as draft
<% end %>
end
<%# =>  <button name="post[draft]" value="true" type="submit">  %>
<%#       Save as draft                                         %>
<%#     </button>                                               %>
```

Co-authored-by: Rafael Mendonça França <[email protected]>

Author: seanpdoyle

actionview/CHANGELOG.md

@@ -1,3 +1,19 @@
+*   Support passing a Symbol as the first argument to `FormBuilder#button`:
+
+    ```ruby
+    form.button(:draft, value: true)
+    # => <button name="post[draft]" value="true" type="submit">Create post</button>
+
+    form.button(:draft, value: true) do
+      content_tag(:strong, "Save as draft")
+    end
+    # =>  <button name="post[draft]" value="true" type="submit">
+    #       <strong>Save as draft</strong>
+    #     </button>
+    ```
+
+    *Sean Doyle*
+
 *   Introduce the `field_name` view helper, along with the
     `FormBuilder#field_name` counterpart:
 

actionview/lib/action_view/helpers/form_helper.rb

@@ -2597,6 +2597,9 @@ def submit(value = nil, options = {})
       #   button("Create post")
       #   # => <button name='button' type='submit'>Create post</button>
       #
+      #   button(:draft, value: true)
+      #   # => <button name="post[draft]" value="true" type="submit">Create post</button>
+      #
       #   button do
       #     content_tag(:strong, 'Ask me!')
       #   end
@@ -2611,8 +2614,20 @@ def submit(value = nil, options = {})
       #   #      <strong>Create post</strong>
       #   #    </button>
       #
+      #   button(:draft, value: true) do
+      #     content_tag(:strong, "Save as draft")
+      #   end
+      #   # =>  <button name="post[draft]" value="true" type="submit">
+      #   #       <strong>Save as draft</strong>
+      #   #     </button>
+      #
       def button(value = nil, options = {}, &block)
-        value, options = nil, value if value.is_a?(Hash)
+        case value
+        when Hash
+          value, options = nil, value
+        when Symbol
+          value, options[:name] = nil, field_name(value)
+        end
         value ||= submit_default_value
 
         if block_given?

actionview/test/template/form_helper_test.rb

@@ -2532,6 +2532,30 @@ def test_submit_with_object_which_is_namespaced
     end
   end
 
+  def test_button_with_method_name
+    form_for(@post) do |f|
+      concat f.button(:secret, value: true)
+    end
+
+    expected = whole_form("/posts/123", "edit_post_123", "edit_post", method: "patch") do
+      %(<button type="submit" name="post[secret]" value="true">Update Post</button>)
+    end
+
+    assert_dom_equal expected, output_buffer
+  end
+
+  def test_button_with_method_name_and_block
+    form_for(@post) do |f|
+      concat f.button(:secret, value: true) { "Update secret Post" }
+    end
+
+    expected = whole_form("/posts/123", "edit_post_123", "edit_post", method: "patch") do
+      %(<button type="submit" name="post[secret]" value="true">Update secret Post</button>)
+    end
+
+    assert_dom_equal expected, output_buffer
+  end
+
   def test_button_with_get_formmethod_attribute
     form_for(@post, as: :another_post) do |f|
       concat f.button "GET", formmethod: :get