fix: capture live run metrics in PerfJsonReporter instead of re-reading baselines

Author: iamAbhi-916

packages/@react-native-windows/perf-testing/src/ci/PerfJsonReporter.ts

@@ -78,11 +78,11 @@ export class PerfJsonReporter {
     const suites: SuiteResult[] = [];
 
     for (const suite of results.testResults) {
-      // Load the snapshot file for this test suite (written by toMatchPerfSnapshot)
+      // Use live run metrics captured during the test run
       const {file: snapshotFilePath} = SnapshotManager.getSnapshotPath(
         suite.testFilePath,
       );
-      const snapshots = SnapshotManager.load(snapshotFilePath);
+      const snapshots = SnapshotManager.getRunMetrics(snapshotFilePath) ?? {};
 
       const passed = suite.testResults.filter(
         t => t.status === 'passed',

packages/@react-native-windows/perf-testing/src/matchers/snapshotManager.ts

@@ -26,8 +26,27 @@ export type SnapshotFile = Record<string, SnapshotEntry>;
 
 /**
  * Manages reading and writing of perf snapshot files.
+ * Also maintains an in-memory registry of current-run metrics
+ * so the CI reporter can access live results
  */
 export class SnapshotManager {
+  /** In-memory store of metrics captured during the current test run. */
+  private static readonly _runMetrics: Map<string, SnapshotFile> = new Map();
+  static recordRunMetric(
+    snapshotFilePath: string,
+    key: string,
+    entry: SnapshotEntry,
+  ): void {
+    if (!SnapshotManager._runMetrics.has(snapshotFilePath)) {
+      SnapshotManager._runMetrics.set(snapshotFilePath, {});
+    }
+    SnapshotManager._runMetrics.get(snapshotFilePath)![key] = entry;
+  }
+
+  static getRunMetrics(snapshotFilePath: string): SnapshotFile | null {
+    return SnapshotManager._runMetrics.get(snapshotFilePath) ?? null;
+  }
+
   static getSnapshotPath(testFilePath: string): {
     dir: string;
     file: string;

packages/@react-native-windows/perf-testing/src/matchers/toMatchPerfSnapshot.ts

@@ -168,6 +168,13 @@ expect.extend({
 
     const threshold: PerfThreshold = {...DEFAULT_THRESHOLD, ...customThreshold};
 
+    // Always record the live metrics for the CI reporter
+    SnapshotManager.recordRunMetric(snapshotFile, snapshotKey, {
+      metrics: received,
+      threshold,
+      capturedAt: new Date().toISOString(),
+    });
+
     // UPDATE MODE or FIRST RUN: write new baseline
     // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
     if (isUpdateMode || !baseline) {