Fix infinite loop when diffing non-equatable recursive objects (#137)

* Fix infinite loop when diffing non-equatable recursive objects

Fixes #136.

* wip

* wip

* wip

* wip

* wip

Author: stephencelis

.github/workflows/ci.yml

@@ -43,19 +43,22 @@ jobs:
         run: make test-linux SWIFT_VERSION=${{ matrix.swift }}
 
   wasm:
-    name: SwiftWasm
+    name: Wasm
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: bytecodealliance/actions/wasmtime/setup@v1
-      - uses: swiftwasm/setup-swiftwasm@v1
-        with:
-          swift-version: "wasm-5.9.2-RELEASE"
-      - name: Build tests
-        # Extend the stack size to avoid stack overflow in the test suites
-        run: swift build --triple wasm32-unknown-wasi --build-tests -Xlinker -z -Xlinker stack-size=$((1024 * 1024))
-      - name: Run tests
-        run: wasmtime .build/debug/swift-custom-dumpPackageTests.wasm
+      - name: Install Swift and Swift SDK for WebAssembly
+        run: |
+          PREFIX=/opt/swift
+          set -ex
+          curl -f -o /tmp/swift.tar.gz "https://download.swift.org/swift-6.0.3-release/ubuntu2204/swift-6.0.3-RELEASE/swift-6.0.3-RELEASE-ubuntu22.04.tar.gz"
+          sudo mkdir -p $PREFIX; sudo tar -xzf /tmp/swift.tar.gz -C $PREFIX --strip-component 1
+          $PREFIX/usr/bin/swift sdk install https://github.com/swiftwasm/swift/releases/download/swift-wasm-6.0.3-RELEASE/swift-wasm-6.0.3-RELEASE-wasm32-unknown-wasi.artifactbundle.zip --checksum 31d3585b06dd92de390bacc18527801480163188cd7473f492956b5e213a8618
+          echo "$PREFIX/usr/bin" >> $GITHUB_PATH
+
+      - name: Build
+        run: swift build --swift-sdk wasm32-unknown-wasi -Xlinker -z -Xlinker stack-size=$((1024 * 1024))
 
   windows:
     name: Windows
@@ -117,4 +120,4 @@ jobs:
         with:
           api-level: 29
           arch: x86_64
-          script: ~/test-toolchain.sh
+          script: ~/test-toolchain.sh

Sources/CustomDump/Internal/Mirror.swift

@@ -28,6 +28,10 @@ extension Mirror {
 
 func isMirrorEqual(_ lhs: Any, _ rhs: Any) -> Bool {
   guard let lhs = lhs as? any Equatable else {
+    let lhsType = type(of: lhs)
+    if lhsType is AnyClass, lhsType == type(of: rhs), lhs as AnyObject === rhs as AnyObject {
+      return true
+    }
     let lhsMirror = Mirror(customDumpReflecting: lhs)
     let rhsMirror = Mirror(customDumpReflecting: rhs)
     guard

Tests/CustomDumpTests/DiffTests.swift

@@ -1290,6 +1290,15 @@ final class DiffTests: XCTestCase {
       """
     )
   }
+
+  func testRecursion() {
+    class Object {
+      var child: Object?
+    }
+    let object = Object()
+    object.child = object
+    XCTAssertNil(diff(object, object))
+  }
 }
 
 private class Shared: _CustomDiffObject, Equatable {