Allow value option on labels for easier building of dynamic radio buttons/checkboxes

lib/phoenix_html/form.ex

@@ -1433,6 +1433,9 @@ defmodule Phoenix.HTML.Form do
         "E-mail Address"
       end
       #=> <label class="control-label" for="user_email">E-mail Address</label>
+
+      label :user, :newsletters, "Recieve all newsletters", value: "all"
+      #=> <label for="user_newsletters_all">Recieve all newsletters</label>
   """
   def label(form, field) do
     label(form, field, humanize(field), [])
@@ -1457,15 +1460,25 @@ defmodule Phoenix.HTML.Form do
   See `label/2`.
   """
   def label(form, field, text, opts) when is_binary(text) and is_list(opts) do
-    opts = Keyword.put_new(opts, :for, input_id(form, field))
+    opts = label_options(form, field, opts)
     content_tag(:label, text, opts)
   end
 
   def label(form, field, opts, do: block) do
-    opts = Keyword.put_new(opts, :for, input_id(form, field))
+    opts = label_options(form, field, opts)
     content_tag(:label, opts, do: block)
   end
 
+  defp label_options(form, field, opts) do
+    {opts, input_id} =
+      case Keyword.pop(opts, :value) do
+        {nil, opts} -> {opts, input_id(form, field)}
+        {value, opts} -> {opts, input_id(form, field, value)}
+      end
+
+    Keyword.put_new(opts, :for, input_id)
+  end
+
   # Normalize field name to string version
   defp field_to_string(field) when is_atom(field), do: Atom.to_string(field)
   defp field_to_string(field) when is_binary(field), do: field

test/phoenix_html/form_test.exs

@@ -1173,6 +1173,10 @@ defmodule Phoenix.HTML.FormTest do
              ~s(<label class="test-label" for="search_key">Hello</label>)
   end
 
+  test "label/4 with for_value option" do
+    assert safe_form(&label(&1, :key, value: "1")) == ~s(<label for="search_key_1">Key</label>)
+  end
+
   test "label/3 with a block" do
     assert safe_form(&label(&1, :key, do: "Hello")) == ~s(<label for="search_key">Hello</label>)
   end