Add GraphNode example for Cxx TMs (#41766)

Summary:
Pull Request resolved: #41766

Changelog: [Internal]

Adds a simple example showing a recursive node, stored inside a collection in a Cxx TM.

Currently we can't auto-generate [the necessary C++ Types](https://reactnative.dev/docs/next/the-new-architecture/cxx-custom-types#struct-generator) - but we can add it later if this scenarios becomes really common.

Reviewed By: rshest

Differential Revision: D51783974

fbshipit-source-id: 7352db1a354cd7da32febc650f7cc5e10dd16d2d

Author: christophpurrer

packages/rn-tester/NativeCxxModuleExample/NativeCxxModuleExample.cpp

@@ -65,6 +65,16 @@ std::string NativeCxxModuleExample::consumeCustomHostObject(
   return value->a_ + std::to_string(value->b_);
 }
 
+GraphNode NativeCxxModuleExample::getGraphNode(
+    jsi::Runtime& rt,
+    GraphNode arg) {
+  if (arg.neighbors) {
+    arg.neighbors->emplace_back(GraphNode{.label = "top"});
+    arg.neighbors->emplace_back(GraphNode{.label = "down"});
+  }
+  return arg;
+}
+
 NativeCxxModuleExampleCxxEnumFloat NativeCxxModuleExample::getNumEnum(
     jsi::Runtime& rt,
     NativeCxxModuleExampleCxxEnumInt arg) {

packages/rn-tester/NativeCxxModuleExample/NativeCxxModuleExample.h

@@ -90,6 +90,42 @@ struct CustomHostObjectRef {
 
 using CustomHostObject = HostObjectWrapper<CustomHostObjectRef>;
 
+#pragma mark - recursive objects
+struct GraphNode {
+  std::string label;
+  std::optional<std::vector<GraphNode>> neighbors;
+};
+
+template <>
+struct Bridging<GraphNode> {
+  static GraphNode fromJs(
+      jsi::Runtime& rt,
+      const jsi::Object& value,
+      const std::shared_ptr<CallInvoker>& jsInvoker) {
+    GraphNode result{
+        bridging::fromJs<std::string>(
+            rt, value.getProperty(rt, "label"), jsInvoker),
+        bridging::fromJs<std::optional<std::vector<GraphNode>>>(
+            rt, value.getProperty(rt, "neighbors"), jsInvoker)};
+    return result;
+  }
+
+  static jsi::Object toJs(
+      jsi::Runtime& rt,
+      const GraphNode value,
+      const std::shared_ptr<CallInvoker>& jsInvoker) {
+    auto result = facebook::jsi::Object(rt);
+    result.setProperty(rt, "label", bridging::toJs(rt, value.label, jsInvoker));
+    if (value.neighbors) {
+      result.setProperty(
+          rt,
+          "neighbors",
+          bridging::toJs(rt, value.neighbors.value(), jsInvoker));
+    }
+    return result;
+  }
+};
+
 #pragma mark - implementation
 class NativeCxxModuleExample
     : public NativeCxxModuleExampleCxxSpec<NativeCxxModuleExample> {
@@ -120,6 +156,8 @@ class NativeCxxModuleExample
       jsi::Runtime& rt,
       std::shared_ptr<CustomHostObject> arg);
 
+  GraphNode getGraphNode(jsi::Runtime& rt, GraphNode arg);
+
   NativeCxxModuleExampleCxxEnumFloat getNumEnum(
       jsi::Runtime& rt,
       NativeCxxModuleExampleCxxEnumInt arg);

packages/rn-tester/NativeCxxModuleExample/NativeCxxModuleExample.js

@@ -56,13 +56,19 @@ export type ValueStruct = {|
 
 export type CustomHostObject = {};
 
+export type GraphNode = {
+  label: string,
+  neighbors?: Array<GraphNode>,
+};
+
 export interface Spec extends TurboModule {
   +getArray: (arg: Array<ObjectStruct | null>) => Array<ObjectStruct | null>;
   +getBool: (arg: boolean) => boolean;
   +getConstants: () => ConstantsStruct;
   +getCustomEnum: (arg: EnumInt) => EnumInt;
   +getCustomHostObject: () => CustomHostObject;
   +consumeCustomHostObject: (customHostObject: CustomHostObject) => string;
+  +getGraphNode: (arg: GraphNode) => GraphNode;
   +getNumEnum: (arg: EnumInt) => EnumFloat;
   +getStrEnum: (arg: EnumNone) => EnumStr;
   +getMap: (arg: {[key: string]: ?number}) => {[key: string]: ?number};

packages/rn-tester/js/examples/TurboModule/NativeCxxModuleExampleExample.js

@@ -42,6 +42,8 @@ type Examples =
   | 'getBool'
   | 'getConstants'
   | 'getCustomEnum'
+  | 'getCustomHostObject'
+  | 'getGraphNode'
   | 'getNumEnum'
   | 'getStrEnum'
   | 'getMap'
@@ -102,6 +104,11 @@ class NativeCxxModuleExampleExample extends React.Component<{||}, State> {
       NativeCxxModuleExample?.consumeCustomHostObject(
         NativeCxxModuleExample?.getCustomHostObject(),
       ),
+    getGraphNode: () =>
+      NativeCxxModuleExample?.getGraphNode({
+        label: 'root',
+        neighbors: [{label: 'left'}, {label: 'right'}],
+      }),
     getNumEnum: () => NativeCxxModuleExample?.getNumEnum(EnumInt.IB),
     getStrEnum: () => NativeCxxModuleExample?.getStrEnum(EnumNone.NB),
     getNumber: () => NativeCxxModuleExample?.getNumber(99.95),