Fix label for attribute when not scoped to model

Defers assigning label `for` value to later in `initialize` method,
ensuring the `scope_id_false: false` option is respected.

Closes #3695

Author: myabc

app/lib/primer/forms/dsl/input.rb

@@ -58,7 +58,6 @@ def initialize(builder:, form:, **system_arguments)
           @input_arguments = system_arguments
           @input_arguments.delete(:id) unless @input_arguments[:id].present?
           @label_arguments = @input_arguments.delete(:label_arguments) || {}
-          @label_arguments[:for] = id if id.present?
 
           @label_arguments[:class] = class_names(
             @label_arguments[:class],
@@ -102,6 +101,8 @@ def initialize(builder:, form:, **system_arguments)
           end
           # rubocop:enable Style/IfUnlessModifier
 
+          @label_arguments[:for] = @input_arguments[:id]
+
           # Whether or not to wrap the component in a FormControl, which renders a
           # label above and validation message beneath the input.
           @form_control = @input_arguments.delete(:form_control) { true }

test/lib/primer/forms/input_test.rb

@@ -104,6 +104,7 @@ def test_removes_model_scope_from_name_and_id
     end
 
     assert_selector "input#ultimate_answer[name=ultimate_answer]"
+    assert_selector "label[for=ultimate_answer]"
   end
 
   def test_uses_given_id
@@ -116,5 +117,6 @@ def test_uses_given_id
     end
 
     assert_selector "input#foobar[name=ultimate_answer]"
+    assert_selector "label[for=foobar]"
   end
 end