[Fizz] Track Key Path (#27243)

Tracks the currently executing parent path of a task, using the name of
the component and the key or index.

This can be used to uniquely identify an instance of a component between
requests - assuming nothing in the parents has changed. Even if it has
changed, if things are properly keyed, it should still line up.

It's not used yet but we'll need this for two separate features so
should land this so we can stack on top.

Can be passed to `JSON.stringify(...)` to generate a unique key.

DiffTrain build for [98f3f14](98f3f14)

compiled/facebook-www/REVISION

@@ -1 +1 @@
-e50531692010bbda2a4627b07c7c810c3770a52a
+98f3f14d2e06fb785103296318204cd154d5d0ed

compiled/facebook-www/ReactDOMServer-dev.classic.js

@@ -19,7 +19,7 @@ if (__DEV__) {
 var React = require("react");
 var ReactDOM = require("react-dom");
 
-var ReactVersion = "18.3.0-www-classic-f7f9d058";
+var ReactVersion = "18.3.0-www-classic-5c145eb3";
 
 // This refers to a WWW module.
 var warningWWW = require("warning");
@@ -9692,7 +9692,10 @@ function getStackByComponentStackNode(componentStack) {
 
 var ReactCurrentDispatcher = ReactSharedInternals.ReactCurrentDispatcher;
 var ReactCurrentCache = ReactSharedInternals.ReactCurrentCache;
-var ReactDebugCurrentFrame = ReactSharedInternals.ReactDebugCurrentFrame;
+var ReactDebugCurrentFrame = ReactSharedInternals.ReactDebugCurrentFrame; // Linked list representing the identity of a component given the component/tag name and key.
+// The name might be minified but we assume that it's going to be the same generated name. Typically
+// because it's just the same compiled output in practice.
+
 var PENDING = 0;
 var COMPLETED = 1;
 var FLUSHED = 2;
@@ -9787,6 +9790,7 @@ function createRequest(
     null,
     rootSegment,
     abortSet,
+    null,
     emptyContextObject,
     rootContextSnapshot,
     emptyTreeContext
@@ -9835,6 +9839,7 @@ function createTask(
   blockedBoundary,
   blockedSegment,
   abortSet,
+  keyPath,
   legacyContext,
   context,
   treeContext
@@ -9855,6 +9860,7 @@ function createTask(
     blockedBoundary: blockedBoundary,
     blockedSegment: blockedSegment,
     abortSet: abortSet,
+    keyPath: keyPath,
     legacyContext: legacyContext,
     context: context,
     treeContext: treeContext,
@@ -10060,7 +10066,7 @@ function renderSuspenseBoundary(request, task, props) {
 
   try {
     // We use the safe form because we don't handle suspending here. Only error handling.
-    renderNode(request, task, content);
+    renderNode(request, task, content, 0);
     pushSegmentFinale(
       contentRootSegment.chunks,
       request.responseState,
@@ -10113,6 +10119,7 @@ function renderSuspenseBoundary(request, task, props) {
     parentBoundary,
     boundarySegment,
     fallbackAbortSet,
+    task.keyPath,
     task.legacyContext,
     task.context,
     task.treeContext
@@ -10144,7 +10151,7 @@ function renderHostElement(request, task, type, props) {
   segment.formatContext = getChildFormatContext(prevContext, type, props); // We use the non-destructive form because if something suspends, we still
   // need to pop back up and finish this subtree of HTML.
 
-  renderNode(request, task, children); // We expect that errors will fatal the whole task and that we don't need
+  renderNode(request, task, children, 0); // We expect that errors will fatal the whole task and that we don't need
   // the correct context. Therefore this is not in a finally.
 
   segment.formatContext = prevContext;
@@ -10206,13 +10213,13 @@ function finishClassComponent(request, task, instance, Component, props) {
         childContextTypes
       );
       task.legacyContext = mergedContext;
-      renderNodeDestructive(request, task, null, nextChildren);
+      renderNodeDestructive(request, task, null, nextChildren, 0);
       task.legacyContext = previousContext;
       return;
     }
   }
 
-  renderNodeDestructive(request, task, null, nextChildren);
+  renderNodeDestructive(request, task, null, nextChildren, 0);
 }
 
 function renderClassComponent(request, task, Component, props) {
@@ -10323,12 +10330,12 @@ function renderIndeterminateComponent(
       task.treeContext = pushTreeContext(prevTreeContext, totalChildren, index);
 
       try {
-        renderNodeDestructive(request, task, null, value);
+        renderNodeDestructive(request, task, null, value, 0);
       } finally {
         task.treeContext = prevTreeContext;
       }
     } else {
-      renderNodeDestructive(request, task, null, value);
+      renderNodeDestructive(request, task, null, value, 0);
     }
   }
 
@@ -10430,12 +10437,12 @@ function renderForwardRef(request, task, prevThenableState, type, props, ref) {
     task.treeContext = pushTreeContext(prevTreeContext, totalChildren, index);
 
     try {
-      renderNodeDestructive(request, task, null, children);
+      renderNodeDestructive(request, task, null, children, 0);
     } finally {
       task.treeContext = prevTreeContext;
     }
   } else {
-    renderNodeDestructive(request, task, null, children);
+    renderNodeDestructive(request, task, null, children, 0);
   }
 
   popComponentStackInDEV(task);
@@ -10497,7 +10504,7 @@ function renderContextConsumer(request, task, context, props) {
 
   var newValue = readContext$1(context);
   var newChildren = render(newValue);
-  renderNodeDestructive(request, task, null, newChildren);
+  renderNodeDestructive(request, task, null, newChildren, 0);
 }
 
 function renderContextProvider(request, task, type, props) {
@@ -10511,7 +10518,7 @@ function renderContextProvider(request, task, type, props) {
   }
 
   task.context = pushProvider(context, value);
-  renderNodeDestructive(request, task, null, children);
+  renderNodeDestructive(request, task, null, children, 0);
   task.context = popProvider(context);
 
   {
@@ -10554,7 +10561,7 @@ function renderOffscreen(request, task, props) {
   else {
     // A visible Offscreen boundary is treated exactly like a fragment: a
     // pure indirection.
-    renderNodeDestructive(request, task, null, props.children);
+    renderNodeDestructive(request, task, null, props.children, 0);
   }
 }
 
@@ -10595,7 +10602,7 @@ function renderElement(request, task, prevThenableState, type, props, ref) {
     case REACT_STRICT_MODE_TYPE:
     case REACT_PROFILER_TYPE:
     case REACT_FRAGMENT_TYPE: {
-      renderNodeDestructive(request, task, null, props.children);
+      renderNodeDestructive(request, task, null, props.children, 0);
       return;
     }
 
@@ -10607,14 +10614,14 @@ function renderElement(request, task, prevThenableState, type, props, ref) {
     case REACT_SUSPENSE_LIST_TYPE: {
       pushBuiltInComponentStackInDEV(task, "SuspenseList"); // TODO: SuspenseList should control the boundaries.
 
-      renderNodeDestructive(request, task, null, props.children);
+      renderNodeDestructive(request, task, null, props.children, 0);
       popComponentStackInDEV(task);
       return;
     }
 
     case REACT_SCOPE_TYPE: {
       {
-        renderNodeDestructive(request, task, null, props.children);
+        renderNodeDestructive(request, task, null, props.children, 0);
         return;
       }
     }
@@ -10719,14 +10726,21 @@ function renderNodeDestructive(
   task, // The thenable state reused from the previous attempt, if any. This is almost
   // always null, except when called by retryTask.
   prevThenableState,
-  node
+  node,
+  childIndex
 ) {
   {
     // In Dev we wrap renderNodeDestructiveImpl in a try / catch so we can capture
     // a component stack at the right place in the tree. We don't do this in renderNode
     // becuase it is not called at every layer of the tree and we may lose frames
     try {
-      return renderNodeDestructiveImpl(request, task, prevThenableState, node);
+      return renderNodeDestructiveImpl(
+        request,
+        task,
+        prevThenableState,
+        node,
+        childIndex
+      );
     } catch (x) {
       if (typeof x === "object" && x !== null && typeof x.then === "function");
       else {
@@ -10743,7 +10757,13 @@ function renderNodeDestructive(
 } // This function by it self renders a node and consumes the task by mutating it
 // to update the current execution state.
 
-function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
+function renderNodeDestructiveImpl(
+  request,
+  task,
+  prevThenableState,
+  node,
+  childIndex
+) {
   // Stash the node we're working on. We'll pick up from this task in case
   // something suspends.
   task.node = node; // Handle object types
@@ -10753,9 +10773,14 @@ function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
       case REACT_ELEMENT_TYPE: {
         var element = node;
         var type = element.type;
+        var key = element.key;
         var props = element.props;
         var ref = element.ref;
+        var name = getComponentNameFromType(type);
+        var prevKeyPath = task.keyPath;
+        task.keyPath = [task.keyPath, name, key == null ? childIndex : key];
         renderElement(request, task, prevThenableState, type, props, ref);
+        task.keyPath = prevKeyPath;
         return;
       }
 
@@ -10791,13 +10816,13 @@ function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
           }
         }
 
-        renderNodeDestructive(request, task, null, resolvedNode);
+        renderNodeDestructive(request, task, null, resolvedNode, childIndex);
         return;
       }
     }
 
     if (isArray(node)) {
-      renderChildrenArray(request, task, node);
+      renderChildrenArray(request, task, node, childIndex);
       return;
     }
 
@@ -10826,7 +10851,7 @@ function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
             step = iterator.next();
           } while (!step.done);
 
-          renderChildrenArray(request, task, children);
+          renderChildrenArray(request, task, children, childIndex);
           return;
         }
 
@@ -10850,7 +10875,8 @@ function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
         request,
         task,
         null,
-        unwrapThenable(thenable)
+        unwrapThenable(thenable),
+        childIndex
       );
     }
 
@@ -10863,7 +10889,8 @@ function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
         request,
         task,
         null,
-        readContext$1(context)
+        readContext$1(context),
+        childIndex
       );
     } // $FlowFixMe[method-unbinding]
 
@@ -10912,19 +10939,28 @@ function renderNodeDestructiveImpl(request, task, prevThenableState, node) {
   }
 }
 
-function renderChildrenArray(request, task, children) {
+function renderChildrenArray(request, task, children, childIndex) {
+  var prevKeyPath = task.keyPath;
   var totalChildren = children.length;
 
   for (var i = 0; i < totalChildren; i++) {
     var prevTreeContext = task.treeContext;
     task.treeContext = pushTreeContext(prevTreeContext, totalChildren, i);
 
     try {
-      // We need to use the non-destructive form so that we can safely pop back
+      var node = children[i];
+
+      if (isArray(node) || getIteratorFn(node)) {
+        // Nested arrays behave like a "fragment node" which is keyed.
+        // Therefore we need to add the current index as a parent key.
+        task.keyPath = [task.keyPath, "", childIndex];
+      } // We need to use the non-destructive form so that we can safely pop back
       // up and render the sibling if something suspends.
-      renderNode(request, task, children[i]);
+
+      renderNode(request, task, node, i);
     } finally {
       task.treeContext = prevTreeContext;
+      task.keyPath = prevKeyPath;
     }
   }
 }
@@ -10951,6 +10987,7 @@ function spawnNewSuspendedTask(request, task, thenableState, x) {
     task.blockedBoundary,
     newSegment,
     task.abortSet,
+    task.keyPath,
     task.legacyContext,
     task.context,
     task.treeContext
@@ -10969,7 +11006,7 @@ function spawnNewSuspendedTask(request, task, thenableState, x) {
 } // This is a non-destructive form of rendering a node. If it suspends it spawns
 // a new task and restores the context of this task to what it was before.
 
-function renderNode(request, task, node) {
+function renderNode(request, task, node, childIndex) {
   // Store how much we've pushed at this point so we can reset it in case something
   // suspended partially through writing something.
   var segment = task.blockedSegment;
@@ -10980,14 +11017,15 @@ function renderNode(request, task, node) {
   var previousFormatContext = task.blockedSegment.formatContext;
   var previousLegacyContext = task.legacyContext;
   var previousContext = task.context;
+  var previousKeyPath = task.keyPath;
   var previousComponentStack = null;
 
   {
     previousComponentStack = task.componentStack;
   }
 
   try {
-    return renderNodeDestructive(request, task, null, node);
+    return renderNodeDestructive(request, task, null, node, childIndex);
   } catch (thrownValue) {
     resetHooksState(); // Reset the write pointers to where we started.
 
@@ -11010,7 +11048,8 @@ function renderNode(request, task, node) {
 
       task.blockedSegment.formatContext = previousFormatContext;
       task.legacyContext = previousLegacyContext;
-      task.context = previousContext; // Restore all active ReactContexts to what they were before.
+      task.context = previousContext;
+      task.keyPath = previousKeyPath; // Restore all active ReactContexts to what they were before.
 
       switchContext(previousContext);
 
@@ -11024,7 +11063,8 @@ function renderNode(request, task, node) {
       // functions in case nothing throws so we don't use "finally" here.
       task.blockedSegment.formatContext = previousFormatContext;
       task.legacyContext = previousLegacyContext;
-      task.context = previousContext; // Restore all active ReactContexts to what they were before.
+      task.context = previousContext;
+      task.keyPath = previousKeyPath; // Restore all active ReactContexts to what they were before.
 
       switchContext(previousContext);
 
@@ -11286,7 +11326,7 @@ function retryTask(request, task) {
     // component suspends again, the thenable state will be restored.
     var prevThenableState = task.thenableState;
     task.thenableState = null;
-    renderNodeDestructive(request, task, prevThenableState, task.node);
+    renderNodeDestructive(request, task, prevThenableState, task.node, 0);
     pushSegmentFinale(
       segment.chunks,
       request.responseState,