Fix and add test

panel/io/cache.py

@@ -435,7 +435,7 @@ def wrapped_func(*args, **kwargs):
                     func_cache[hash_value] = (ret, time, 0, time)
             return ret
 
-    def clear(session_context):
+    def clear():
         global func_hash
         # clear called before anything is cached.
         if 'func_hash' not in globals():
@@ -449,10 +449,13 @@ def clear(session_context):
         else:
             cache = state._memoize_cache.get(func_hash, {})
         cache.clear()
+
     wrapped_func.clear = clear
 
     if per_session and state.curdoc and state.curdoc.session_context:
-        state.curdoc.on_session_destroyed(clear)
+        def server_clear(session_context):
+            clear()
+        state.curdoc.on_session_destroyed(server_clear)
 
     try:
         wrapped_func.__dict__.update(func.__dict__)

panel/tests/io/test_cache.py

@@ -3,10 +3,13 @@
 import pathlib
 import time
 
+from collections import Counter
+
 import numpy as np
 import pandas as pd
 import param
 import pytest
+import requests
 
 try:
     import diskcache
@@ -15,7 +18,8 @@
 diskcache_available = pytest.mark.skipif(diskcache is None, reason="requires diskcache")
 
 from panel.io.cache import _find_hash_func, cache
-from panel.io.state import set_curdoc
+from panel.io.state import set_curdoc, state
+from panel.tests.util import serve_and_wait
 
 ################
 # Test hashing #
@@ -219,6 +223,26 @@ def test_per_session_cache(document):
         assert fn(a=0, b=0) == 0
     assert fn(a=0, b=0) == 1
 
+def test_per_session_cache_server(port):
+    counts = Counter()
+
+    @cache(per_session=True)
+    def get_data():
+        counts[state.curdoc] += 1
+        return "Some data"
+
+    def app():
+        get_data()
+        get_data()
+        return
+
+    serve_and_wait(app, port=port)
+
+    requests.get(f"http://localhost:{port}/")
+    requests.get(f"http://localhost:{port}/")
+
+    assert list(counts.values()) == [1, 1]
+
 @pytest.mark.xdist_group("cache")
 @diskcache_available
 def test_disk_cache():