Consider form action and method changing as changed

lib/phoenix_html/form.ex

@@ -64,6 +64,8 @@ defmodule Phoenix.HTML.Form do
             id: nil,
             name: nil,
             data: nil,
+            action: nil,
+            method: nil,
             hidden: [],
             params: %{},
             errors: [],
@@ -74,6 +76,8 @@ defmodule Phoenix.HTML.Form do
           source: Phoenix.HTML.FormData.t(),
           name: String.t(),
           data: %{field => term},
+          action: nil | atom() | String.t(),
+          method: nil | atom() | String.t(),
           params: %{binary => term},
           hidden: Keyword.t(),
           options: Keyword.t(),
@@ -191,9 +195,9 @@ defmodule Phoenix.HTML.Form do
   @doc """
   Receives two forms structs and checks if the given field changed.
 
-  The field will have changed if either its associated value or errors
-  changed. This is mostly used for optimization engines as an extension
-  of the `Access` behaviour.
+  The field will have changed if either its associated value, errors,
+  action, method, or implementation changed. This is mostly used for optimization
+  engines as an extension of the `Access` behaviour.
   """
   @spec input_changed?(t, t, field()) :: boolean()
   def input_changed?(
@@ -202,7 +206,8 @@ defmodule Phoenix.HTML.Form do
         field
       )
       when is_atom(field) or is_binary(field) do
-    impl1 != impl2 or id1 != id2 or name1 != name2 or
+    impl1 != impl2 or id1 != id2 or name1 != name2 or form1.action != form2.action or
+      form1.method != form2.method or
       field_errors(errors1, field) != field_errors(errors2, field) or
       impl1.input_value(source1, form1, field) != impl2.input_value(source2, form2, field)
   end

lib/phoenix_html/form_data.ex

@@ -56,6 +56,10 @@ defprotocol Phoenix.HTML.FormData do
       applies if the field value is a list and no parameters were
       sent through the form.
 
+    * `:action` - The form action, such as the HTML `action` attribute
+      or LiveView action.
+
+    * `:method` - The form method, such as the HTML `method` attribute.
   """
   @spec to_form(t, Phoenix.HTML.Form.t(), Phoenix.HTML.Form.field(), Keyword.t()) ::
           [Phoenix.HTML.Form.t()]
@@ -79,6 +83,8 @@ defimpl Phoenix.HTML.FormData, for: Map do
   def to_form(conn_or_atom_or_map, opts) do
     {name, params, opts} = name_params_and_opts(conn_or_atom_or_map, opts)
     {errors, opts} = Keyword.pop(opts, :errors, [])
+    {action, opts} = Keyword.pop(opts, :action, nil)
+    {method, opts} = Keyword.pop(opts, :method, nil)
     id = Keyword.get(opts, :id) || name
 
     unless is_binary(id) or is_nil(id) do
@@ -93,6 +99,8 @@ defimpl Phoenix.HTML.FormData, for: Map do
       params: params,
       data: %{},
       errors: errors,
+      action: action,
+      method: method,
       options: opts
     }
   end
@@ -118,6 +126,8 @@ defimpl Phoenix.HTML.FormData, for: Map do
     {name, opts} = Keyword.pop(opts, :as)
     {id, opts} = Keyword.pop(opts, :id)
     {hidden, opts} = Keyword.pop(opts, :hidden, [])
+    {action, opts} = Keyword.pop(opts, :action)
+    {method, opts} = Keyword.pop(opts, :method)
 
     id = to_string(id || form.id <> "_#{field}")
     name = to_string(name || form.name <> "[#{field}]")
@@ -133,6 +143,8 @@ defimpl Phoenix.HTML.FormData, for: Map do
             id: id,
             name: name,
             data: default,
+            action: action,
+            method: method,
             params: params || %{},
             hidden: hidden,
             options: opts
@@ -157,6 +169,8 @@ defimpl Phoenix.HTML.FormData, for: Map do
             source: conn_or_atom_or_map,
             impl: __MODULE__,
             index: index,
+            action: action,
+            method: method,
             id: id <> "_" <> index_string,
             name: name <> "[" <> index_string <> "]",
             data: data,

test/phoenix_html/form_test.exs

@@ -138,6 +138,13 @@ defmodule Phoenix.HTML.FormTest do
     assert input_changed?(form, form(%{"foo" => "bar"}), "foo")
   end
 
+  test "input_changed? with changed action or method" do
+    form = form(%{}, action: :validate, method: "post")
+    refute input_changed?(form, %{form | action: :validate, method: "post"}, :foo)
+    assert input_changed?(form, %{form | action: :save}, :foo)
+    assert input_changed?(form, %{form | method: "put"}, :foo)
+  end
+
   describe "access" do
     test "without name and atom keys" do
       form =