Auto-sync solution when exercise diff has no files (#8493)

* Auto-sync solution when diff has no files instead of raising error

When a solution's git_important_files_hash differs from the exercise's
but the actual git diff produces no interesting file changes, auto-sync
the solution to the latest exercise version instead of returning a 400
error and reporting to Sentry. The frontend now gracefully handles the
empty files case with an auto-updated notice.

Closes #8456

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Adjust styling of modal

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
Co-authored-by: dem4ron <demaaron88@gmail.com>

Author: 3 people

app/controllers/api/solutions_controller.rb

@@ -102,13 +102,7 @@ def unpublish
   def diff
     files = Git::Exercise::GenerateDiffBetweenVersions.(@solution.exercise, @solution.git_slug, @solution.git_sha)
 
-    # TODO: (Optional): Change this to always be a 200 and handle the empty files in React
-    if files.present?
-      status = 200
-    else
-      status = 400
-      Sentry.capture_exception(RuntimeError.new("No files were found during solution diff"))
-    end
+    Solution::UpdateToLatestExerciseVersion.(@solution) if files.blank?
 
     render json: {
       diff: {
@@ -121,7 +115,7 @@ def diff
           update: Exercism::Routes.sync_api_solution_url(@solution.uuid)
         }
       }
-    }, status:
+    }, status: :ok
   end
 
   def sync

app/css/modals/update-exercise.css

@@ -5,6 +5,9 @@
         @apply flex flex-col;
         width: 80%;
     }
+    &:has(.auto-updated-notice) .--modal-content {
+        max-width: 500px;
+    }
     & .header {
         @apply mb-16;
         & h2 {

app/javascript/components/modals/ExerciseUpdateModal.tsx

@@ -3,7 +3,7 @@
 import React from 'react'
 import { FetchingBoundary } from '../FetchingBoundary'
 import { Modal, ModalProps } from './Modal'
-import { Icon } from '../common'
+import { Icon, GraphicalIcon } from '../common'
 import { useRequestQuery } from '../../hooks/request-query'
 import { ExerciseUpdateForm } from './exercise-update-modal/ExerciseUpdateForm'
 import { Exercise } from '../types'
@@ -43,13 +43,47 @@ export const ExerciseUpdateModal = ({
         defaultError={DEFAULT_ERROR}
       >
         {data ? (
-          <ExerciseUpdateForm diff={data.diff} onCancel={props.onClose} />
+          data.diff.files.length > 0 ? (
+            <ExerciseUpdateForm diff={data.diff} onCancel={props.onClose} />
+          ) : (
+            <AutoUpdatedNotice onClose={props.onClose} />
+          )
         ) : null}
       </FetchingBoundary>
     </Modal>
   )
 }
 
+const AutoUpdatedNotice = ({ onClose }: { onClose: () => void }) => {
+  const { t } = useAppTranslation('components/modals/ExerciseUpdateModal.tsx')
+  return (
+    <div className="auto-updated-notice flex flex-col items-center text-center">
+      <GraphicalIcon
+        icon="completed-check-circle"
+        height={64}
+        width={64}
+        className="mb-20"
+      />
+      <h2 className="text-h3 mb-8">
+        {t('exerciseUpdateModal.autoUpdatedTitle')}
+      </h2>
+      <p className="text-p-large mb-24">
+        {t('exerciseUpdateModal.autoUpdatedBody')}
+      </p>
+      <button
+        type="button"
+        className="btn-primary btn-m"
+        onClick={() => {
+          onClose()
+          window.location.reload()
+        }}
+      >
+        {t('exerciseUpdateModal.continue')}
+      </button>
+    </div>
+  )
+}
+
 const LoadingComponent = () => {
   const { t } = useAppTranslation('components/modals/ExerciseUpdateModal.tsx')
   return (

app/javascript/i18n/en/components-modals-ExerciseUpdateModal.tsx.ts

@@ -1,6 +1,8 @@
 // namespace: components/modals/ExerciseUpdateModal.tsx
 export default {
   'exerciseUpdateModal.loadingExerciseDiff': 'Loading exercise diff',
-  'exerciseUpdateModal.sorryCantWorkOutWhatNeedsUpdating':
-    "Sorry - it seems that we can't work out what needs updating for this exercise. We've been alerted and will have a look.",
+  'exerciseUpdateModal.autoUpdatedTitle': 'Exercise Updated',
+  'exerciseUpdateModal.autoUpdatedBody':
+    'This exercise has been automatically updated to the latest version. There are no file changes to review.',
+  'exerciseUpdateModal.continue': 'Continue',
 }

test/controllers/api/solutions_controller_test.rb

@@ -173,22 +173,17 @@ class API::SolutionsControllerTest < API::BaseTestCase
     assert_equal expected, actual
   end
 
-  test "Diff returns 400 if diff does not contain files" do
+  test "Diff auto-syncs and returns 200 when diff does not contain files" do
     user = create :user
     setup_user(user)
     solution = create(:concept_solution, user:)
-    get diff_api_solution_path(solution.uuid), headers: @headers, as: :json
-
-    assert_response :bad_request
-  end
-
-  test "Sentry is alerted if diff does not contain files" do
-    user = create :user
-    setup_user(user)
-    solution = create(:concept_solution, user:)
-    Sentry.expects(:capture_exception).with(RuntimeError.new("No files were found during solution diff"))
+    Solution::UpdateToLatestExerciseVersion.expects(:call).with(solution)
 
     get diff_api_solution_path(solution.uuid), headers: @headers, as: :json
+
+    assert_response :ok
+    response_body = JSON.parse(response.body)
+    assert_empty response_body.dig("diff", "files")
   end
 
   ########