Add FlaskSessionCacheHandler (#833)

Updated examples/app.py
Updated CHANGELOG.md and appropriate docs.

examples/app.py

@@ -27,7 +27,6 @@ import os
 from flask import Flask, session, request, redirect
 from flask_session import Session
 import spotipy
-import uuid
 
 app = Flask(__name__)
 app.config['SECRET_KEY'] = os.urandom(64)
@@ -35,57 +34,44 @@ app.config['SESSION_TYPE'] = 'filesystem'
 app.config['SESSION_FILE_DIR'] = './.flask_session/'
 Session(app)
 
-caches_folder = './.spotify_caches/'
-if not os.path.exists(caches_folder):
-    os.makedirs(caches_folder)
-
-def session_cache_path():
-    return caches_folder + session.get('uuid')
 
 @app.route('/')
 def index():
-    if not session.get('uuid'):
-        # Step 1. Visitor is unknown, give random ID
-        session['uuid'] = str(uuid.uuid4())
 
-    cache_handler = spotipy.cache_handler.CacheFileHandler(cache_path=session_cache_path())
+    cache_handler = spotipy.cache_handler.FlaskSessionCacheHandler(session)
     auth_manager = spotipy.oauth2.SpotifyOAuth(scope='user-read-currently-playing playlist-modify-private',
-                                                cache_handler=cache_handler, 
-                                                show_dialog=True)
+                                               cache_handler=cache_handler,
+                                               show_dialog=True)
 
     if request.args.get("code"):
-        # Step 3. Being redirected from Spotify auth page
+        # Step 2. Being redirected from Spotify auth page
         auth_manager.get_access_token(request.args.get("code"))
         return redirect('/')
 
     if not auth_manager.validate_token(cache_handler.get_cached_token()):
-        # Step 2. Display sign in link when no token
+        # Step 1. Display sign in link when no token
         auth_url = auth_manager.get_authorize_url()
         return f'<h2><a href="{auth_url}">Sign in</a></h2>'
 
-    # Step 4. Signed in, display data
+    # Step 3. Signed in, display data
     spotify = spotipy.Spotify(auth_manager=auth_manager)
     return f'<h2>Hi {spotify.me()["display_name"]}, ' \
            f'<small><a href="/sign_out">[sign out]<a/></small></h2>' \
            f'<a href="/playlists">my playlists</a> | ' \
            f'<a href="/currently_playing">currently playing</a> | ' \
-		   f'<a href="/current_user">me</a>' \
+        f'<a href="/current_user">me</a>' \
+
 
 
 @app.route('/sign_out')
 def sign_out():
-    try:
-        # Remove the CACHE file (.cache-test) so that a new user can authorize.
-        os.remove(session_cache_path())
-        session.clear()
-    except OSError as e:
-        print ("Error: %s - %s." % (e.filename, e.strerror))
+    session.pop("token_info", None)
     return redirect('/')
 
 
 @app.route('/playlists')
 def playlists():
-    cache_handler = spotipy.cache_handler.CacheFileHandler(cache_path=session_cache_path())
+    cache_handler = spotipy.cache_handler.FlaskSessionCacheHandler(session)
     auth_manager = spotipy.oauth2.SpotifyOAuth(cache_handler=cache_handler)
     if not auth_manager.validate_token(cache_handler.get_cached_token()):
         return redirect('/')
@@ -96,7 +82,7 @@ def playlists():
 
 @app.route('/currently_playing')
 def currently_playing():
-    cache_handler = spotipy.cache_handler.CacheFileHandler(cache_path=session_cache_path())
+    cache_handler = spotipy.cache_handler.FlaskSessionCacheHandler(session)
     auth_manager = spotipy.oauth2.SpotifyOAuth(cache_handler=cache_handler)
     if not auth_manager.validate_token(cache_handler.get_cached_token()):
         return redirect('/')
@@ -109,7 +95,7 @@ def currently_playing():
 
 @app.route('/current_user')
 def current_user():
-    cache_handler = spotipy.cache_handler.CacheFileHandler(cache_path=session_cache_path())
+    cache_handler = spotipy.cache_handler.FlaskSessionCacheHandler(session)
     auth_manager = spotipy.oauth2.SpotifyOAuth(cache_handler=cache_handler)
     if not auth_manager.validate_token(cache_handler.get_cached_token()):
         return redirect('/')