add option submits_with to button

README.md

@@ -1068,6 +1068,32 @@ will be rendered as
 
 (some unimportant HTML attributes have been removed for simplicity)
 
+### Turbo submits with
+There is a turbo attribute [(data-turbo-submits-with)](https://turbo.hotwired.dev/reference/attributes) that replaces the content of a submit button while the request is processing. Turbo supports it on both `<button>` and `<input type="submit">` elements, but an `<input>` can only show plain text, so HTML content such as a spinner needs a `<button>`. Use `f.button`, or `f.primary` with `render_as_button: true`, when the replacement content is HTML.
+
+Plain text works with the normal submit input:
+```erb
+<%= f.primary "Save", data: { turbo_submits_with: "Saving..." } %>
+```
+
+```html
+<input class="btn btn-primary" data-turbo-submits-with="Saving..." name="commit" type="submit" value="Save">
+```
+
+You can have `bootstrap_form` put up a default bootstrap spinner while the request is processing with `f.spinner`, or provide your own HTML:
+```erb
+<%= f.button "Save", data: { turbo_submits_with: f.spinner } %>
+
+<%= f.primary "Save", render_as_button: true, data: { turbo_submits_with: f.spinner } %>
+
+<%= f.button "Save", data: { turbo_submits_with: "<span>Loading...</span>" } %>
+```
+
+```html
+<button class="btn btn-secondary" data-turbo-submits-with="<span>Loading...</span>" name="button" type="submit">Save</button>
+```
+
+
 ## Rich Text Areas AKA Trix Editor
 
 ![Example 38](demo/doc/screenshots/bootstrap/readme/38_example.png "Example 38")

lib/bootstrap_form/helpers/bootstrap.rb

@@ -96,6 +96,14 @@ def static_class
         "form-control-plaintext"
       end
 
+      def spinner
+        tag.div(class: "text-center") do
+          tag.div(class: "spinner-border spinner-border-sm", role: "status") do
+            tag.span("Loading...", class: "visually-hidden")
+          end
+        end
+      end
+
       private
 
       def attach_input(options, key)

test/bootstrap_other_components_test.rb

@@ -152,6 +152,22 @@ class BootstrapOtherComponentsTest < ActionView::TestCase
                            @builder.button("<span>I'm HTML!</span> in a button!".html_safe, extra_class: "test-button")
   end
 
+  test "regular button has turbo-submits-with default spinner" do
+    expected = <<~HTML
+      <button class="btn btn-secondary" data-turbo-submits-with='&lt;div class="text-center"&gt;&lt;div class="spinner-border spinner-border-sm" role="status"&gt;&lt;span class="visually-hidden"&gt;Loading...&lt;/span&gt;&lt;/div&gt;&lt;/div&gt;' name="button" type="submit">Submit with Spinner</button>
+    HTML
+    assert_equivalent_html expected,
+                           @builder.button("Submit with Spinner", data: { turbo_submits_with: @builder.spinner })
+  end
+
+  test "regular button has turbo-submits-with custom HTML" do
+    expected = <<~HTML
+      <button class="btn btn-secondary" data-turbo-submits-with="<span>Loading...</span>" name="button" type="submit">Submit with Spinner</button>
+    HTML
+    assert_equivalent_html expected,
+                           @builder.button("Submit with Spinner", data: { turbo_submits_with: "<span>Loading...</span>" })
+  end
+
   test "submit button defaults to rails action name" do
     expected = '<input class="btn btn-secondary" name="commit" type="submit" value="Create User" />'
     assert_equivalent_html expected, @builder.submit
@@ -182,6 +198,21 @@ class BootstrapOtherComponentsTest < ActionView::TestCase
     assert_equivalent_html expected, @builder.primary("Submit Form", extra_class: "test-button")
   end
 
+  test "primary button with plain-text turbo-submits-with still renders a submit input" do
+    expected = <<~HTML
+      <input class="btn btn-primary" data-turbo-submits-with="Saving..." name="commit" type="submit" value="Submit Form" />
+    HTML
+    assert_equivalent_html expected, @builder.primary("Submit Form", data: { turbo_submits_with: "Saving..." })
+  end
+
+  test "primary button with render_as_button and turbo-submits-with spinner renders a button" do
+    expected = <<~HTML
+      <button class="btn btn-primary" data-turbo-submits-with='&lt;div class="text-center"&gt;&lt;div class="spinner-border spinner-border-sm" role="status"&gt;&lt;span class="visually-hidden"&gt;Loading...&lt;/span&gt;&lt;/div&gt;&lt;/div&gt;' name="button" type="submit">Submit Form</button>
+    HTML
+    assert_equivalent_html expected,
+                           @builder.primary("Submit Form", render_as_button: true, data: { turbo_submits_with: @builder.spinner })
+  end
+
   test "primary button can render as HTML button" do
     expected = %q(<button class="btn btn-primary" name="button" type="submit"><span>I'm HTML!</span> Submit Form</button>)
     assert_equivalent_html expected,