From b529a826e89ac7d2fdce45b42c5fe7223d4723df Mon Sep 17 00:00:00 2001
From: Mikhail Golubev <mikhail.golubev@jetbrains.com>
Date: Mon, 6 Feb 2017 12:20:22 +0300
Subject: [PATCH] PY-21180 PyUtil#getParametrizedCachedValue uses
 ConcurrentHashMap

in case multiple read-only threads update the same cache simultaneously
---
 python/src/com/jetbrains/python/psi/PyUtil.java | 15 ++++-----------
 1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/python/src/com/jetbrains/python/psi/PyUtil.java b/python/src/com/jetbrains/python/psi/PyUtil.java
index 3e368553c1fa..dc656f0a5e66 100644
--- a/python/src/com/jetbrains/python/psi/PyUtil.java
+++ b/python/src/com/jetbrains/python/psi/PyUtil.java
@@ -846,19 +846,12 @@ public class PyUtil {
     });
   }
 
-  private static final Object NULL_VALUE = new Object();
   public static <T, P> T getParameterizedCachedValue(@NotNull PsiElement element, @Nullable P param, @NotNull NullableFunction<P, T> f) {
-    final Map<P, Object> cache = CachedValuesManager.getCachedValue(element, new CachedValueProvider<Map<P, Object>>() {
-      @Nullable
-      @Override
-      public Result<Map<P, Object>> compute() {
-        // TODO should be concurrent map instead
-        return Result.create(Maps.newHashMap(), PsiModificationTracker.MODIFICATION_COUNT);
-      }
+    final Map<Optional<P>, Optional<T>> cache = CachedValuesManager.getCachedValue(element, () -> {
+      // concurrent hash map is a null-hostile collection
+      return CachedValueProvider.Result.create(Maps.newConcurrentMap(), PsiModificationTracker.MODIFICATION_COUNT);
     });
-    final Object wrapped = cache.computeIfAbsent(param, p -> ObjectUtils.notNull(f.fun(param), NULL_VALUE));
-    //noinspection unchecked
-    return (T)ObjectUtils.nullizeByCondition(wrapped, NULL_VALUE::equals);
+    return cache.computeIfAbsent(Optional.ofNullable(param), p -> Optional.ofNullable(f.fun(param))).orElse(null);
   }
 
   /**