fix(core): skip stale recomputations and prevent lost file changes in daemon (#34424)

## Current Behavior

When file changes arrive rapidly, the daemon triggers multiple
concurrent project graph recomputations that all run to completion —
wasting CPU/memory on redundant work and returning stale results.

Additionally, after processing file changes, the daemon clears all
tracked files indiscriminately. Files that changed mid-recomputation are
silently lost and never reflected in the project graph until another
unrelated file change arrives.

## Expected Behavior

Stale recomputations detect when a newer one has started and exit early,
chaining to the newer promise so callers always get the freshest result.

File change tracking now uses versioned maps. Each batch of file watcher
events gets a unique version, and only files matching the snapshotted
version are cleared after processing. Files that changed
mid-recomputation are preserved and picked up by the next cycle.

Author: leosvelperez

packages/nx/src/daemon/server/project-graph-incremental-recomputation.ts

@@ -66,8 +66,10 @@ export let fileMapWithFiles:
 export let currentProjectFileMapCache: FileMapCache | undefined;
 export let currentProjectGraph: ProjectGraph | undefined;
 
-const collectedUpdatedFiles = new Set<string>();
-const collectedDeletedFiles = new Set<string>();
+// Maps file path to a version counter that increments on each modification.
+// This lets us detect mid-flight re-modifications when clearing processed files.
+const collectedUpdatedFiles = new Map<string, number>();
+const collectedDeletedFiles = new Map<string, number>();
 const projectGraphRecomputationListeners = new Set<
   (
     projectGraph: ProjectGraph,
@@ -79,6 +81,8 @@ let storedWorkspaceConfigHash: string | undefined;
 let waitPeriod = 100;
 let scheduledTimeoutId;
 let knownExternalNodes: Record<string, ProjectGraphExternalNode> = {};
+let fileChangeCounter = 0;
+let recomputationGeneration = 0;
 
 export async function getCachedSerializedProjectGraphPromise(): Promise<SerializedProjectGraph> {
   try {
@@ -167,14 +171,15 @@ export function addUpdatedAndDeletedFiles(
   updatedFiles: string[],
   deletedFiles: string[]
 ) {
+  ++fileChangeCounter;
   for (let f of [...createdFiles, ...updatedFiles]) {
     collectedDeletedFiles.delete(f);
-    collectedUpdatedFiles.add(f);
+    collectedUpdatedFiles.set(f, fileChangeCounter);
   }
 
   for (let f of deletedFiles) {
     collectedUpdatedFiles.delete(f);
-    collectedDeletedFiles.add(f);
+    collectedDeletedFiles.set(f, fileChangeCounter);
   }
 
   // Notify file change listeners immediately when files change
@@ -272,9 +277,6 @@ async function processCollectedUpdatedAndDeletedFiles(
         );
       }
     }
-
-    collectedUpdatedFiles.clear();
-    collectedDeletedFiles.clear();
   } catch (e) {
     // this is expected
     // for instance, project.json can be incorrect or a file we are trying to has
@@ -294,10 +296,17 @@ async function processCollectedUpdatedAndDeletedFiles(
 async function processFilesAndCreateAndSerializeProjectGraph(
   plugins: LoadedNxPlugin[]
 ): Promise<SerializedProjectGraph> {
+  const myGeneration = ++recomputationGeneration;
+
+  // Helper to check if this recomputation is stale (a newer one has started)
+  const isStale = () => myGeneration !== recomputationGeneration;
+
   try {
     performance.mark('hash-watched-changes-start');
-    const updatedFiles = [...collectedUpdatedFiles.values()];
-    const deletedFiles = [...collectedDeletedFiles.values()];
+    const updatedFilesSnapshot = new Map(collectedUpdatedFiles);
+    const deletedFilesSnapshot = new Map(collectedDeletedFiles);
+    const updatedFiles = [...updatedFilesSnapshot.keys()];
+    const deletedFiles = [...deletedFilesSnapshot.keys()];
     let updatedFileHashes = updateFilesInContext(
       workspaceRoot,
       updatedFiles,
@@ -312,8 +321,8 @@ async function processFilesAndCreateAndSerializeProjectGraph(
     serverLogger.requestLog(
       `Updated workspace context based on watched changes, recomputing project graph...`
     );
-    serverLogger.requestLog([...updatedFiles.values()]);
-    serverLogger.requestLog([...deletedFiles]);
+    serverLogger.requestLog(updatedFiles);
+    serverLogger.requestLog(deletedFiles);
     const nxJson = readNxJson(workspaceRoot);
     global.NX_GRAPH_CREATION = true;
 
@@ -334,11 +343,36 @@ async function processFilesAndCreateAndSerializeProjectGraph(
         throw e;
       }
     }
+
+    // Early exit if a newer recomputation has started - chain to the newer one
+    if (isStale()) {
+      return cachedSerializedProjectGraphPromise;
+    }
+
     await processCollectedUpdatedAndDeletedFiles(
       projectConfigurationsResult,
       updatedFileHashes,
       deletedFiles
     );
+
+    // Only remove files whose version matches the snapshot — if the version
+    // is higher, the file was modified again mid-flight and needs reprocessing.
+    for (const [f, version] of updatedFilesSnapshot) {
+      if (collectedUpdatedFiles.get(f) === version) {
+        collectedUpdatedFiles.delete(f);
+      }
+    }
+    for (const [f, version] of deletedFilesSnapshot) {
+      if (collectedDeletedFiles.get(f) === version) {
+        collectedDeletedFiles.delete(f);
+      }
+    }
+
+    // Early exit if a newer recomputation has started - chain to the newer one
+    if (isStale()) {
+      return cachedSerializedProjectGraphPromise;
+    }
+
     const g = await createAndSerializeProjectGraph(projectConfigurationsResult);
 
     delete global.NX_GRAPH_CREATION;