Allow objects with memoized values to be marshaled/unmarshaled across Ruby processes (#51)

Author: obrie

README.md

@@ -190,6 +190,36 @@ a.memoized?(:call) # => true
 a.memoized?(:execute) # => false
 ```
 
+### Marshal-compatible Memoization
+
+In order for objects to be marshaled and loaded in a different Ruby process,
+hashed arguments must be disabled in order for memoized values to be retained.
+Note that this can have a performance impact if the memoized method contains
+arguments.
+
+```ruby
+Memery.use_hashed_arguments = false
+
+class A
+  include Memery
+
+  memoize def call
+    puts "calculating"
+    42
+  end
+end
+
+a = A.new
+a.call
+
+Marshal.dump(a)
+# => "\x04\bo:\x06A\x06:\x1D@_memery_memoized_values{\x06:\tcallS:3Memery::ClassMethods::MemoizationModule::Cache\a:\vresulti/:\ttimef\x14663237.14822323"
+
+# ...in another Ruby process:
+a = Marshal.load("\x04\bo:\x06A\x06:\x1D@_memery_memoized_values{\x06:\tcallS:3Memery::ClassMethods::MemoizationModule::Cache\a:\vresulti/:\ttimef\x14663237.14822323")
+a.call # => 42
+```
+
 ## Differences from Other Gems
 
 Memery is similar to [Memoist](https://github.com/matthewrudy/memoist), but it doesn't override methods. Instead, it uses Ruby 2's `Module.prepend` feature. This approach is cleaner, allowing you to inspect the original method body with `method(:x).super_method.source`, and it ensures that subclasses' methods function properly. If you redefine a memoized method in a subclass, it won't be memoized by default. You can memoize it normally without needing an awkward `identifier: ` argument, and it will just work:

benchmark.rb

@@ -32,6 +32,10 @@ def base_find(char)
     memoize def find_new(char)
       base_find(char)
     end
+
+    memoize def find_optional(*)
+      base_find("z")
+    end
   end
 end
 
@@ -43,6 +47,10 @@ def test_with_args
   Foo.find_new("d")
 end
 
+def test_empty_args
+  Foo.find_optional
+end
+
 Benchmark.ips do |x|
   x.report("test_no_args") { test_no_args }
 end
@@ -51,6 +59,14 @@ def test_with_args
   x.report("test_no_args") { 100.times { test_no_args } }
 end
 
+Benchmark.ips do |x|
+  x.report("test_empty_args") { test_empty_args }
+end
+
+Benchmark.memory do |x|
+  x.report("test_empty_args") { 100.times { test_empty_args } }
+end
+
 Benchmark.ips do |x|
   x.report("test_with_args") { test_with_args }
 end
@@ -59,4 +75,14 @@ def test_with_args
   x.report("test_with_args") { 100.times { test_with_args } }
 end
 
+Memery.use_hashed_arguments = false
+Benchmark.ips do |x|
+  x.report("test_with_args_no_hash") { test_with_args }
+end
+
+Benchmark.memory do |x|
+  x.report("test_with_args_no_hash") { 100.times { test_with_args } }
+end
+Memery.use_hashed_arguments = true
+
 puts "```"

lib/memery.rb

@@ -4,11 +4,15 @@
 
 module Memery
   class << self
+    attr_accessor :use_hashed_arguments
+
     def monotonic_clock
       Process.clock_gettime(Process::CLOCK_MONOTONIC)
     end
   end
 
+  @use_hashed_arguments = true
+
   OUR_BLOCK = lambda do
     extend(ClassMethods)
     include(InstanceMethods)
@@ -68,19 +72,25 @@ def fresh?(ttl)
         end
       end
 
+      # rubocop:disable Metrics/MethodLength
       def define_memoized_method!(klass, method_name, condition: nil, ttl: nil)
-        method_key = "#{method_name}_#{object_id}"
-
+        # Include a suffix in the method key to differentiate between methods of the same name
+        # being memoized throughout a class inheritance hierarchy
+        method_key = "#{method_name}_#{klass.name || object_id}"
         original_visibility = method_visibility(klass, method_name)
-        original_arity = klass.instance_method(method_name).arity
 
         define_method(method_name) do |*args, &block|
           if block || (condition && !instance_exec(&condition))
             return super(*args, &block)
           end
 
           cache_store = (@_memery_memoized_values ||= {})
-          cache_key = original_arity.zero? ? method_key : [method_key, *args].hash
+          cache_key = if args.empty?
+                        method_key
+                      else
+                        key_parts = [method_key, *args]
+                        Memery.use_hashed_arguments ? key_parts.hash : key_parts
+                      end
           cache = cache_store[cache_key]
 
           return cache.result if cache&.fresh?(ttl)
@@ -95,6 +105,7 @@ def define_memoized_method!(klass, method_name, condition: nil, ttl: nil)
         ruby2_keywords(method_name)
         send(original_visibility, method_name)
       end
+      # rubocop:enable Metrics/MethodLength
 
       private
 

spec/memery_spec.rb

@@ -153,6 +153,7 @@ class H
 
   before { CALLS.clear }
   before { B_CALLS.clear }
+  before { Memery.use_hashed_arguments = true }
 
   let(:unmemoized_class) do
     Class.new do
@@ -263,6 +264,27 @@ class H
     end
   end
 
+  context "anonymous inherited class" do
+    let(:anonymous_class) do
+      Class.new(A) do
+        memoize def m_args(x, y)
+          B_CALLS << [x, y]
+          super(1, 2)
+          100
+        end
+      end
+    end
+
+    subject(:b) { anonymous_class.new }
+
+    specify do
+      values = [ b.m_args(1, 1), b.m_args(1, 2), b.m_args(1, 1) ]
+      expect(values).to eq([100, 100, 100])
+      expect(CALLS).to eq([[1, 2]])
+      expect(B_CALLS).to eq([[1, 1], [1, 2]])
+    end
+  end
+
   context "module" do
     subject(:c) { C.new }
 
@@ -336,6 +358,26 @@ class H
     end
   end
 
+  context "without hashed arguments" do
+    before { Memery.use_hashed_arguments = false }
+
+    context "methods without args" do
+      specify do
+        values = [ a.m, a.m_nil, a.m, a.m_nil ]
+        expect(values).to eq([:m, nil, :m, nil])
+        expect(CALLS).to eq([:m, nil])
+      end
+    end
+
+    context "method with args" do
+      specify do
+        values = [ a.m_args(1, 1), a.m_args(1, 1), a.m_args(1, 2) ]
+        expect(values).to eq([[1, 1], [1, 1], [1, 2]])
+        expect(CALLS).to eq([[1, 1], [1, 2]])
+      end
+    end
+  end
+
   describe ":condition option" do
     before do
       a.environment = environment