fix: handle redis outages and unify share update error flow

Author: alvin000009238

app/routes/share.py

@@ -26,6 +26,14 @@ def create_share_link():
         if not data or not isinstance(data, dict):
             return jsonify({'error': 'No data provided or invalid format'}), 400
 
+        student_no = session.get('student_no')
+        if not student_no:
+            return jsonify({'error': 'Authentication required'}), 401
+
+        redis_client = current_app.config.get('REDIS_CLIENT')
+        if redis_client is None:
+            return jsonify({'error': 'Share service unavailable'}), 503
+
         # Turnstile 人機驗證
         ts_ok, ts_err = verify_turnstile_token(
             data.get('turnstile_token'),
@@ -35,7 +43,6 @@ def create_share_link():
             return jsonify({'error': ts_err}), 403
 
         # 速率限制檢查（在 Turnstile 之後）
-        redis_client = current_app.config.get('REDIS_CLIENT')
         if redis_client:
             try:
                 # 較寬鬆的速率限制：每小時 (3600 秒) 10 次
@@ -60,12 +67,7 @@ def create_share_link():
         if not valid:
             return jsonify({'error': err}), 400
 
-        student_no = session.get('student_no')
-        if not student_no:
-            return jsonify({'error': 'Authentication required'}), 401
-
         share_id = generate_share_id()
-        redis_client = current_app.config['REDIS_CLIENT']
         share_ttl = current_app.config['SHARE_TTL']
         write_shared_data(redis_client, share_id, cleaned, share_ttl)
         write_share_metadata(redis_client, share_id, student_no, share_ttl)
@@ -85,7 +87,9 @@ def update_share_link(share_id):
         if not data or not isinstance(data, dict):
             return jsonify({'error': 'No data provided or invalid format'}), 400
 
-        redis_client = current_app.config['REDIS_CLIENT']
+        redis_client = current_app.config.get('REDIS_CLIENT')
+        if redis_client is None:
+            return jsonify({'error': 'Share service unavailable'}), 503
 
         requester_student_no = session.get('student_no')
         if requester_student_no is None:

frontend/share.js

@@ -16,25 +16,20 @@ export function getActiveShareId() {
 
 export async function updateActiveShare(gradesData) {
     const shareId = getActiveShareId();
-    if (!shareId || !gradesData) return;
-
-    try {
-        const res = await fetch(`/api/share/${shareId}`, {
-            method: 'PUT',
-            headers: { 'Content-Type': 'application/json' },
-            credentials: 'include',
-            body: JSON.stringify(gradesData)
-        });
+    if (!shareId || !gradesData) return { attempted: false, ok: false, status: null };
 
-        if (!res.ok) {
-            if (res.status === 404 || res.status === 403) {
-                localStorage.removeItem(ACTIVE_SHARE_ID_KEY);
-            }
-            return;
-        }
-    } catch (error) {
-        console.error('更新分享失敗:', error);
+    const res = await fetch(`/api/share/${shareId}`, {
+        method: 'PUT',
+        headers: { 'Content-Type': 'application/json' },
+        credentials: 'include',
+        body: JSON.stringify(gradesData)
+    });
+
+    if (!res.ok && (res.status === 404 || res.status === 403)) {
+        localStorage.removeItem(ACTIVE_SHARE_ID_KEY);
     }
+
+    return { attempted: true, ok: res.ok, status: res.status };
 }
 
 export function setupShareFeature() {

tests/backend/test_share_routes.py

@@ -1,6 +1,4 @@
 import json
-import os
-
 import pytest
 
 from app import create_app
@@ -40,7 +38,7 @@ def ttl(self, key):
 
 @pytest.fixture
 def client(monkeypatch):
-    os.environ['APP_ENV'] = 'testing'
+    monkeypatch.setenv('APP_ENV', 'testing')
     app = create_app()
     app.config['TESTING'] = True
     app.config['SHARE_TTL'] = 7200
@@ -153,3 +151,28 @@ def test_share_update_rate_limited(client):
     assert last_response is not None
     assert last_response.status_code == 429
     assert 'Retry-After' in last_response.headers
+
+
+def test_share_create_returns_503_when_redis_unavailable(client):
+    with client.session_transaction() as sess:
+        sess['student_no'] = 'A123'
+
+    client.application.config['REDIS_CLIENT'] = None
+    create_res = client.post('/api/share', json=_share_payload())
+
+    assert create_res.status_code == 503
+    assert create_res.get_json()['error'] == 'Share service unavailable'
+
+
+def test_share_update_returns_503_when_redis_unavailable(client):
+    with client.session_transaction() as sess:
+        sess['student_no'] = 'A123'
+
+    create_res = client.post('/api/share', json=_share_payload())
+    share_id = create_res.get_json()['id']
+
+    client.application.config['REDIS_CLIENT'] = None
+    update_res = client.put(f'/api/share/{share_id}', json=_share_payload())
+
+    assert update_res.status_code == 503
+    assert update_res.get_json()['error'] == 'Share service unavailable'