util.cache: Keep eviction candidate if callback resized to make room

Previously either the old or the new values would be rejected, even if
the cache was resized to allow more items.

2 files changed, 29 insertions, 3 deletions

diff --git a/spec/util_cache_spec.lua b/spec/util_cache_spec.lua
index 2cb7b7dd..d4e609ed 100644
--- a/spec/util_cache_spec.lua
+++ b/spec/util_cache_spec.lua
@@ -388,5 +388,26 @@ describe("util.cache", function()
 			c:resize(3);
 			assert.same({"v5", "v4", "v3"}, vs(c));
 		end);
+
+		it("eviction stuff", function ()
+			local c;
+			c = cache.new(4, function(_k,_v)
+				if c.size < 10 then
+					c:resize(c.size*2);
+				end
+			end)
+			for i = 1,20 do
+				c:set(i,i)
+			end
+			assert.equal(16, c.size);
+			assert.is_nil(c:get(1))
+			assert.is_nil(c:get(4))
+			assert.equal(5, c:get(5))
+			assert.equal(20, c:get(20))
+			c:resize(4)
+			assert.equal(20, c:get(20))
+			assert.equal(17, c:get(17))
+			assert.is_nil(c:get(10))
+		end)
 	end);
 end);
diff --git a/util/cache.lua b/util/cache.lua
index cd1b4544..a72a535f 100644
--- a/util/cache.lua
+++ b/util/cache.lua
@@ -54,12 +54,17 @@ function cache_methods:set(k, v)
 	if self._count == self.size then
 		local tail = self._tail;
 		local on_evict, evicted_key, evicted_value = self._on_evict, tail.key, tail.value;
-		if on_evict ~= nil and (on_evict == false or on_evict(evicted_key, evicted_value) == false) then
+
+		local do_evict = on_evict and on_evict(evicted_key, evicted_value);
+
+		if do_evict == false then
 			-- Cache is full, and we're not allowed to evict
 			return false;
+		elseif self._count == self.size then
+			-- Cache wasn't grown
+			_remove(self, tail);
+			self._data[evicted_key] = nil;
 		end
-		_remove(self, tail);
-		self._data[evicted_key] = nil;
 	end
 
 	m = { key = k, value = v, prev = nil, next = nil };