Disable phase date fields when a phase is disabled

The JavaScript involved wasn't working since we removed the disable-date
attribute in commit 73ff6881.

We're also improving the JavaScript in two ways:

First, we trigger the `change` event immediately, so when the page loads
date fields are disabled when phases are disabled.

And second, we don't remove the selected dates when disabling a phase,
so disabling it and enabling it again will keep the selected values.

app/assets/javascripts/legislation_admin.js

@@ -2,21 +2,21 @@
   "use strict";
   App.LegislationAdmin = {
     initialize: function() {
-      $("input[type='checkbox'][data-disable-date]").on({
+      $(".legislation-process-form").find("[name$='enabled]'],[name$='[published]']").on({
         change: function() {
-          var checkbox, date_selector, parent;
+          var checkbox;
           checkbox = $(this);
-          parent = $(this).parents(".row:eq(0)");
+
-          date_selector = $(this).data("disable-date");
+          checkbox.closest("fieldset").find("input[type='text']").each(function() {
-          parent.find("input[type='text'][id^='" + date_selector + "']").each(function() {
             if (checkbox.is(":checked")) {
               $(this).removeAttr("disabled");
             } else {
-              $(this).val("");
+              $(this).prop("disabled", true);
             }
           });
         }
-      });
+      }).trigger("change");
+
       $("#nested_question_options").on("cocoon:after-insert", function() {
         App.Globalize.refresh_visible_translations();
       });

app/assets/stylesheets/layout.scss

@@ -1074,6 +1074,10 @@ form {
     &.error {
       margin-bottom: rem-calc(1);
     }
+
+    &:disabled {
+      background-color: $input-background-disabled;
+    }
   }
 
   [type="checkbox"] + label,

spec/system/admin/legislation/processes_spec.rb

@@ -240,6 +240,44 @@ describe "Admin collaborative legislation" do
       expect(page).not_to have_content "Draft publication"
     end
 
+    scenario "Enabling/disabling a phase enables/disables its date fields", :js do
+      process.update!(published: false)
+
+      visit edit_admin_legislation_process_path(process)
+
+      expect(page).to have_field "start_date", disabled: true
+      expect(page).to have_field "end_date", disabled: true
+
+      check "legislation_process[published]"
+      fill_in "start_date", with: "07/07/2007"
+      fill_in "end_date", with: "08/08/2008"
+      uncheck "legislation_process[published]"
+
+      expect(page).to have_field "start_date", disabled: true
+      expect(page).to have_field "end_date", disabled: true
+
+      check "legislation_process[published]"
+
+      expect(page).to have_field "start_date", disabled: false, with: "07/07/2007"
+      expect(page).to have_field "end_date", disabled: false, with: "08/08/2008"
+    end
+
+    scenario "Enabling/disabling a phase does not enable/disable another phase date fields", :js do
+      process.update!(draft_phase_enabled: false, draft_publication_enabled: false)
+
+      visit edit_admin_legislation_process_path(process)
+
+      expect(page).to have_field "draft_start_date", disabled: true
+      expect(page).to have_field "draft_end_date", disabled: true
+      expect(page).to have_field "draft_publication_date", disabled: true
+
+      check "legislation_process[draft_phase_enabled]"
+
+      expect(page).to have_field "draft_start_date", disabled: false
+      expect(page).to have_field "draft_end_date", disabled: false
+      expect(page).to have_field "draft_publication_date", disabled: true
+    end
+
     scenario "Change proposal categories" do
       visit edit_admin_legislation_process_path(process)
       within(".admin-content") { click_link "Proposals" }