Add match option to Nebulex.Caching

lib/nebulex/caching.ex

@@ -20,6 +20,11 @@ defmodule Nebulex.Caching do
     * `:opts` - Defines the cache options that will be passed as argument
       to the invoked cache function (optional).
 
+  * `:match` - Defines a function that takes one argument and will be used to decide if the
+     cache should be updated or not (optional). If this option is not present,
+     the value will always be updated. Does not have any effect upon eviction
+     since values are always evicted before executing the function logic.
+
   ## Example
 
   Suppose we are using `Ecto` and we want to define some caching functions in
@@ -46,6 +51,10 @@ defmodule Nebulex.Caching do
           Repo.all(query)
         end
 
+        defcacheable get_newest_user(), cache: Cache, key: {User, :latest}, match: &(not is_nil(&1)) do
+          Repo.get_newest(User)
+        end
+
         defupdatable update_user!(%User{} = user, attrs), cache: Cache, key: {User, user.id} do
           user
           |> User.changeset(attrs)
@@ -88,6 +97,10 @@ defmodule Nebulex.Caching do
         defcacheable all(query), cache: Cache do
           # your logic (maybe the loader to retrieve the value from the SoR)
         end
+
+        defcacheable get_newest_user(), cache: Cache, key: {User, :latest}, match: &(not is_nil(&1)) do
+          Repo.get_newest(User)
+        end
       end
 
   The **Read-through** pattern is supported by this macro. The loader to
@@ -172,6 +185,14 @@ defmodule Nebulex.Caching do
         defupdatable update_with_ttl(name), cache: Cache, opts: [ttl: 3600] do
           # your logic (maybe write data to the SoR)
         end
+
+        defcacheable update_when_not_nil(), cache: Cache, match: &match_function/1 do
+          # your logic (maybe write data to the SoR)
+        end
+
+        defp match_function(value) do
+          # your condition to skip updating the cache
+        edn
       end
 
   The **Write-through** pattern is supported by this macro. Your function
@@ -213,6 +234,7 @@ defmodule Nebulex.Caching do
     key_var = Keyword.get(opts, :key)
     keys_var = Keyword.get(opts, :keys)
     opts_var = Keyword.get(opts, :opts, [])
+    match_var = Keyword.get(opts, :match)
     action_logic = action_logic(action, block, opts)
 
     quote do
@@ -221,6 +243,7 @@ defmodule Nebulex.Caching do
         key = unquote(key_var) || :erlang.phash2({unquote(name), unquote(as_args)})
         keys = unquote(keys_var)
         opts = unquote(opts_var)
+        match = unquote(match_var) || fn _ -> true end
 
         unquote(action_logic)
       end
@@ -233,7 +256,12 @@ defmodule Nebulex.Caching do
         value
       else
         value = unquote(block)
-        cache.set(key, value, opts)
+
+        if apply(match, [value]) do
+          cache.set(key, value, opts)
+        else
+          value
+        end
       end
     end
   end
@@ -250,7 +278,12 @@ defmodule Nebulex.Caching do
   defp action_logic(:defupdatable, block, _opts) do
     quote do
       value = unquote(block)
-      cache.set(key, value, opts)
+
+      if apply(match, [value]) do
+        cache.set(key, value, opts)
+      else
+        value
+      end
     end
   end
 

test/nebulex/caching_test.exs

@@ -71,6 +71,16 @@ defmodule Nebulex.CachingTest do
     refute Cache.get(1)
   end
 
+  test "cacheable with match" do
+    refute Cache.get(:x)
+    assert :x == get_with_match(:x)
+    refute Cache.get(:x)
+
+    refute Cache.get(:y)
+    assert :y == get_with_match(:y)
+    assert Cache.get(:y)
+  end
+
   test "cacheable with default key" do
     key = :erlang.phash2({:get_with_default_key, [123, {:foo, "bar"}]})
 
@@ -143,6 +153,14 @@ defmodule Nebulex.CachingTest do
     refute Cache.get(:y)
   end
 
+  test "updatable with match" do
+    assert :ok == set_keys(x: 0, y: 0, z: 0)
+    assert :x == cache_put_with_match(:x)
+    assert :y == cache_put_with_match(:y)
+    assert 0 == Cache.get(:x)
+    assert :y == Cache.get(:y)
+  end
+
   ## Caching Functions
 
   defcacheable get_by_x(x, y \\ "y"), cache: Cache, key: x do
@@ -153,6 +171,10 @@ defmodule Nebulex.CachingTest do
     x
   end
 
+  defcacheable get_with_match(x), cache: Cache, key: x, match: fn x -> x != :x end do
+    x
+  end
+
   defcacheable get_by_xy(x, y), cache: Cache, key: {x, y} do
     {x, y}
   end
@@ -189,6 +211,10 @@ defmodule Nebulex.CachingTest do
     x
   end
 
+  defupdatable cache_put_with_match(x), cache: Cache, key: x, match: fn x -> x != :x end do
+    x
+  end
+
   ## Private Functions
 
   defp set_keys(entries) do