RPP: Ensure enhancedTraceVersion is at top of metadata

Bug: 337909145
Change-Id: Ia224ab4fccde0ba74bc841f15500440c426cf985
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6282447
Auto-Submit: Paul Irish <[email protected]>
Commit-Queue: Connor Clark <[email protected]>
Reviewed-by: Connor Clark <[email protected]>

Author: paulirish

front_end/panels/timeline/SaveFileFormatter.test.ts

@@ -38,6 +38,7 @@ describe('SaveFileFormatter', () => {
       const metadata: Trace.Types.File.MetaData = {
         source: 'DevTools',
         startTime: '1234',
+        modifications: undefined,  // Undefined values are removed within JSON.stringify
         networkThrottling: '4',
         cpuThrottling: 1,
         hardwareConcurrency: 1,
@@ -46,17 +47,20 @@ describe('SaveFileFormatter', () => {
       const formatted = Array.from(Timeline.SaveFileFormatter.traceJsonGenerator(events, metadata)).join('');
       assertValidJSON(formatted);
       assert.strictEqual(formatted, `{"metadata": {
+  "enhancedTraceVersion": 1,
   "source": "DevTools",
   "startTime": "1234",
   "networkThrottling": "4",
   "cpuThrottling": 1,
-  "hardwareConcurrency": 1,
-  "enhancedTraceVersion": 1
+  "hardwareConcurrency": 1
 },
 "traceEvents": [
   {"name":"event_one","tid":0,"pid":0,"ts":0,"cat":"test","ph":"M"},
   {"name":"event_two","tid":0,"pid":0,"ts":0,"cat":"test","ph":"M"}
 ]}\n`);
+      // Extra check that enhancedTraceVersion is first, to ensure maximumTraceFileLengthToDetermineEnhancedTraces has no problem.
+      const trace = JSON.parse(formatted);
+      assert.strictEqual(Object.keys(trace.metadata).at(0), 'enhancedTraceVersion');
     });
 
     it('will emit {} for the metadata if none is provided', async () => {

front_end/panels/timeline/SaveFileFormatter.ts

@@ -44,6 +44,14 @@ export function*
         traceEvents: readonly Trace.Types.Events.Event[],
         metadata: Readonly<Trace.Types.File.MetaData>|null,
         ): IterableIterator<string> {
+  // Ensure that enhancedTraceVersion is placed at the top of metadata. See `maximumTraceFileLengthToDetermineEnhancedTraces`
+  if (metadata?.enhancedTraceVersion) {
+    metadata = {
+      enhancedTraceVersion: metadata.enhancedTraceVersion,
+      ...metadata,
+    };
+  }
+
   yield `{"metadata": ${JSON.stringify(metadata || {}, null, 2)}`;
   yield ',\n"traceEvents": ';
   yield* arrayOfObjectsJsonGenerator(traceEvents);

front_end/panels/timeline/TimelinePanel.ts

@@ -1360,19 +1360,16 @@ export class TimelinePanel extends UI.Panel.Panel implements Client, TimelineMod
     }
     const traceEvents = this.#traceEngineModel.rawTraceEvents(this.#viewMode.traceIndex);
     const metadata = this.#traceEngineModel.metadata(this.#viewMode.traceIndex);
-
-    if (metadata && addModifications) {
-      metadata.modifications = ModificationsManager.activeManager()?.toJSON();
-    } else if (metadata) {
-      delete metadata.modifications;
-    }
-    if (metadata && isEnhancedTraces) {
-      metadata.enhancedTraceVersion = SDK.EnhancedTracesParser.EnhancedTracesParser.enhancedTraceVersion;
-    }
     if (!traceEvents) {
       return;
     }
 
+    if (metadata) {
+      metadata.modifications = addModifications ? ModificationsManager.activeManager()?.toJSON() : undefined;
+      metadata.enhancedTraceVersion =
+          isEnhancedTraces ? SDK.EnhancedTracesParser.EnhancedTracesParser.enhancedTraceVersion : undefined;
+    }
+
     const traceStart = Platform.DateUtilities.toISO8601Compact(new Date());
     let fileName: Platform.DevToolsPath.RawPathString;
     if (metadata?.dataOrigin === Trace.Types.File.DataOrigin.CPU_PROFILE) {