ref(tracing): Remove script evaluation span (#4433)

Tracking the script evaluation span is inconsistent, and often doesn't
show up in most pageload transactions. In addition, the value of this
span is not clear.

To reduce bundle size and complexity, this patch removes the script
evaluation span.

Author: AbhiPrasad

packages/tracing/src/browser/metrics.ts

@@ -44,23 +44,7 @@ export class MetricsInstrumentation {
     logger.log('[Tracing] Adding & adjusting spans using Performance API');
 
     const timeOrigin = msToSec(browserPerformanceTimeOrigin);
-    let entryScriptSrc = '';
-
-    if (global.document && global.document.scripts) {
-      // eslint-disable-next-line @typescript-eslint/prefer-for-of
-      for (let i = 0; i < global.document.scripts.length; i++) {
-        // We go through all scripts on the page and look for 'data-entry'
-        // We remember the name and measure the time between this script finished loading and
-        // our mark 'sentry-tracing-init'
-        if (global.document.scripts[i].dataset.entry === 'true') {
-          entryScriptSrc = global.document.scripts[i].src;
-          break;
-        }
-      }
-    }
 
-    let entryScriptStartTimestamp: number | undefined;
-    let tracingInitMarkStartTime: number | undefined;
     let responseStartTimestamp: number | undefined;
     let requestStartTimestamp: number | undefined;
 
@@ -86,10 +70,6 @@ export class MetricsInstrumentation {
           case 'paint':
           case 'measure': {
             const startTimestamp = addMeasureSpans(transaction, entry, startTime, duration, timeOrigin);
-            if (tracingInitMarkStartTime === undefined && entry.name === 'sentry-tracing-init') {
-              tracingInitMarkStartTime = startTimestamp;
-            }
-
             // capture web vitals
 
             const firstHidden = getVisibilityWatcher();
@@ -112,27 +92,14 @@ export class MetricsInstrumentation {
           }
           case 'resource': {
             const resourceName = (entry.name as string).replace(global.location.origin, '');
-            const endTimestamp = addResourceSpans(transaction, entry, resourceName, startTime, duration, timeOrigin);
-            // We remember the entry script end time to calculate the difference to the first init mark
-            if (entryScriptStartTimestamp === undefined && entryScriptSrc.indexOf(resourceName) > -1) {
-              entryScriptStartTimestamp = endTimestamp;
-            }
+            addResourceSpans(transaction, entry, resourceName, startTime, duration, timeOrigin);
             break;
           }
           default:
           // Ignore other entry types.
         }
       });
 
-    if (entryScriptStartTimestamp !== undefined && tracingInitMarkStartTime !== undefined) {
-      _startChild(transaction, {
-        description: 'evaluation',
-        endTimestamp: tracingInitMarkStartTime,
-        op: 'script',
-        startTimestamp: entryScriptStartTimestamp,
-      });
-    }
-
     this._performanceCursor = Math.max(performance.getEntries().length - 1, 0);
 
     this._trackNavigator(transaction);
@@ -335,11 +302,11 @@ export function addResourceSpans(
   startTime: number,
   duration: number,
   timeOrigin: number,
-): number | undefined {
+): void {
   // we already instrument based on fetch and xhr, so we don't need to
   // duplicate spans here.
   if (entry.initiatorType === 'xmlhttprequest' || entry.initiatorType === 'fetch') {
-    return undefined;
+    return;
   }
 
   const data: Record<string, any> = {};
@@ -363,8 +330,6 @@ export function addResourceSpans(
     startTimestamp,
     data,
   });
-
-  return endTimestamp;
 }
 
 /** Create performance navigation related spans */

packages/tracing/test/browser/metrics.test.ts

@@ -94,7 +94,7 @@ describe('addResourceSpans', () => {
     const startTime = 23;
     const duration = 356;
 
-    const endTimestamp = addResourceSpans(transaction, entry, '/assets/to/css', startTime, duration, timeOrigin);
+    addResourceSpans(transaction, entry, '/assets/to/css', startTime, duration, timeOrigin);
 
     // eslint-disable-next-line @typescript-eslint/unbound-method
     expect(transaction.startChild).toHaveBeenCalledTimes(1);
@@ -110,8 +110,6 @@ describe('addResourceSpans', () => {
       op: 'resource.css',
       startTimestamp: timeOrigin + startTime,
     });
-
-    expect(endTimestamp).toBe(timeOrigin + startTime + duration);
   });
 
   it('creates a variety of resource spans', () => {