Refactor encoder property to weak reference in KeyedContainerImpl and UnkeyedContainerImpl to prevent retain cycles (#239)

* Refactor encoder property to weak reference in KeyedContainerImpl and UnkeyedContainerImpl to prevent retain cycles

* Add memory growth tests for Leaf rendering

* Revert "Refactor encoder property to weak reference in KeyedContainerImpl and UnkeyedContainerImpl to prevent retain cycles"

This reverts commit 9a79408.

* Update Tests/LeafTests/LeafMemoryGrowthTests.swift

Co-authored-by: Gwynne Raskind <gwynne@darkrainfall.org>

---------

Co-authored-by: Gwynne Raskind <gwynne@darkrainfall.org>

Author: makoni

Sources/Leaf/LeafEncoder.swift

@@ -151,7 +151,7 @@ extension LeafEncoder {
     }
 
     private final class KeyedContainerImpl<Key>: KeyedEncodingContainerProtocol, LeafEncodingResolvable where Key: CodingKey {
-        private let encoder: EncoderImpl
+        private unowned let encoder: EncoderImpl
         private var data: [String: any LeafEncodingResolvable] = [:]
         private var nestedEncoderCaptures: [AnyObject] = []
 
@@ -230,7 +230,7 @@ extension LeafEncoder {
     }
 
     private final class UnkeyedContainerImpl: UnkeyedEncodingContainer, LeafEncodingResolvable {
-        private let encoder: EncoderImpl
+        private unowned let encoder: EncoderImpl
         private var data: [any LeafEncodingResolvable] = []
         private var nestedEncoderCaptures: [AnyObject] = []
 

Tests/LeafTests/LeafMemoryGrowthTests.swift

@@ -0,0 +1,50 @@
+import XCTest
+import Leaf
+import LeafKit
+import XCTVapor
+
+/*
+ to profile memory growth, use an sh script like this:
+ ```bash
+ #!/bin/zsh
+ swift test --filter LeafMemoryGrowthTests &
+ sleep 5
+ PID=$(ps aux | grep '[l]eafPackageTests' | awk '{print $2}' | head -n1)
+ echo "leafPackageTests PID: $PID"
+ leaks $PID
+ ```
+*/
+final class LeafMemoryGrowthTests: XCTestCase {
+//    func testRepeatedRenderMemoryGrowth() async throws {
+//        sleep(3) // Keep process alive for leaks profiling
+//        var test = TestFiles()
+//        test.files["/foo.leaf"] = "Hello #(name)!"
+//        
+//        try await withApp { app in
+//            app.views.use(.leaf)
+//            app.leaf.sources = .singleSource(test)
+//            struct Foo: Encodable { var name: String }
+//            // Render with context 1000 times
+//            for _ in 0..<1000 {
+//                _ = try await app.leaf.renderer.render(path: "foo", context: Foo(name: "World")).get()
+//            }
+//        }
+//        sleep(10) // Keep process alive for leaks profiling
+//    }
+//    
+//    func testRepeatedRenderNoContextMemoryGrowth() async throws {
+//        sleep(3) // Keep process alive for leaks profiling
+//        var test = TestFiles()
+//        test.files["/foo.leaf"] = "Hello!"
+//        
+//        try await withApp { app in
+//            app.views.use(.leaf)
+//            app.leaf.sources = .singleSource(test)
+//            // Render without context 1000 times (pass nil context)
+//            for _ in 0..<1000 {
+//                _ = try await app.leaf.renderer.render(path: "foo", context: Optional<Bool>.none).get()
+//            }
+//        }
+//        sleep(10) // Keep process alive for leaks profiling
+//    }
+}