Scheduling Profiler: Show Suspense resource .displayName

packages/react-devtools-scheduling-profiler/src/EventTooltip.css

@@ -46,7 +46,7 @@
   white-space: nowrap;
 }
 
-.DetailsGridURL {
+.DetailsGridLongValue {
   word-break: break-all;
   max-height: 50vh;
   overflow: hidden;

packages/react-devtools-scheduling-profiler/src/EventTooltip.js

@@ -335,6 +335,7 @@ const TooltipSuspenseEvent = ({
     componentName,
     duration,
     phase,
+    promiseName,
     resolution,
     timestamp,
     warning,
@@ -356,6 +357,12 @@ const TooltipSuspenseEvent = ({
         {label}
         <div className={styles.Divider} />
         <div className={styles.DetailsGrid}>
+          {promiseName !== null && (
+            <>
+              <div className={styles.DetailsGridLabel}>Resource:</div>
+              <div className={styles.DetailsGridLongValue}>{promiseName}</div>
+            </>
+          )}
           <div className={styles.DetailsGridLabel}>Status:</div>
           <div>{resolution}</div>
           <div className={styles.DetailsGridLabel}>Timestamp:</div>

packages/react-devtools-scheduling-profiler/src/content-views/SuspenseEventsView.js

@@ -80,6 +80,7 @@ export class SuspenseEventsView extends View {
     this._intrinsicSize = {
       width: duration,
       height: (this._maxDepth + 1) * ROW_WITH_BORDER_HEIGHT,
+      hideScrollBarIfLessThanHeight: ROW_WITH_BORDER_HEIGHT,
       maxInitialHeight: ROW_WITH_BORDER_HEIGHT * MAX_ROWS_TO_SHOW_INITIALLY,
     };
   }
@@ -113,6 +114,7 @@ export class SuspenseEventsView extends View {
       depth,
       duration,
       phase,
+      promiseName,
       resolution,
       timestamp,
       warning,
@@ -208,7 +210,9 @@ export class SuspenseEventsView extends View {
       );
 
       let label = 'suspended';
-      if (componentName != null) {
+      if (promiseName != null) {
+        label = promiseName;
+      } else if (componentName != null) {
         label = `${componentName} ${label}`;
       }
       if (phase !== null) {

packages/react-devtools-scheduling-profiler/src/import-worker/__tests__/preprocessData-test.internal.js

@@ -1195,6 +1195,46 @@ describe('preprocessData', () => {
     `);
   });
 
+  it('should include a suspended resource "displayName" if one is set', async () => {
+    let promise = null;
+    let resolvedValue = null;
+    function readValue(value) {
+      if (resolvedValue !== null) {
+        return resolvedValue;
+      } else if (promise === null) {
+        promise = Promise.resolve(true).then(() => {
+          resolvedValue = value;
+        });
+        promise.displayName = 'Testing displayName';
+      }
+      throw promise;
+    }
+
+    function Component() {
+      const value = readValue(123);
+      return value;
+    }
+
+    if (gate(flags => flags.enableSchedulingProfiler)) {
+      const testMarks = [creactCpuProfilerSample()];
+
+      const root = ReactDOM.createRoot(document.createElement('div'));
+      act(() =>
+        root.render(
+          <React.Suspense fallback="Loading...">
+            <Component />
+          </React.Suspense>,
+        ),
+      );
+
+      testMarks.push(...createUserTimingData(clearedMarks));
+
+      const data = await preprocessData(testMarks);
+      expect(data.suspenseEvents).toHaveLength(1);
+      expect(data.suspenseEvents[0].promiseName).toBe('Testing displayName');
+    }
+  });
+
   describe('warnings', () => {
     describe('long event handlers', () => {
       it('should not warn when React scedules a (sync) update inside of a short event handler', async () => {

packages/react-devtools-scheduling-profiler/src/import-worker/preprocessData.js

@@ -564,9 +564,13 @@ function processTimelineEvent(
 
       // React Events - suspense
       else if (name.startsWith('--suspense-suspend-')) {
-        const [id, componentName, phase, laneBitmaskString] = name
-          .substr(19)
-          .split('-');
+        const [
+          id,
+          componentName,
+          phase,
+          laneBitmaskString,
+          promiseName,
+        ] = name.substr(19).split('-');
         const lanes = getLanesFromTransportDecimalBitmask(laneBitmaskString);
 
         const availableDepths = new Array(
@@ -595,6 +599,7 @@ function processTimelineEvent(
           duration: null,
           id,
           phase: ((phase: any): Phase),
+          promiseName: promiseName || null,
           resolution: 'unresolved',
           resuspendTimestamps: null,
           timestamp: startTime,

packages/react-devtools-scheduling-profiler/src/types.js

@@ -60,6 +60,7 @@ export type SuspenseEvent = {|
   duration: number | null,
   +id: string,
   +phase: Phase | null,
+  promiseName: string | null,
   resolution: 'rejected' | 'resolved' | 'unresolved',
   resuspendTimestamps: Array<number> | null,
   +type: 'suspense',

packages/react-devtools-shared/src/devtools/views/ErrorBoundary/cache.js

@@ -70,6 +70,9 @@ export function findGitHubIssue(errorMessage: string): GitHubIssue | null {
       then(callback) {
         callbacks.add(callback);
       },
+
+      // Optional property used by Scheduling Profiler:
+      displayName: `Searching GitHub issues for error "${errorMessage}"`,
     };
     const wake = () => {
       // This assumes they won't throw.

packages/react-devtools-shared/src/dynamicImportCache.js

@@ -73,6 +73,9 @@ export function loadModule(moduleLoaderFunction: ModuleLoaderFunction): Module {
       then(callback) {
         callbacks.add(callback);
       },
+
+      // Optional property used by Scheduling Profiler:
+      displayName: `Loading module "${moduleLoaderFunction.name}"`,
     };
 
     const wake = () => {

packages/react-devtools-shared/src/hookNamesCache.js

@@ -92,6 +92,9 @@ export function loadHookNames(
       then(callback) {
         callbacks.add(callback);
       },
+
+      // Optional property used by Scheduling Profiler:
+      displayName: `Loading hook names for ${element.displayName || 'Unknown'}`,
     };
 
     let timeoutID;

packages/react-devtools-shared/src/inspectedElementCache.js

@@ -94,7 +94,11 @@ export function inspectElement(
       then(callback) {
         callbacks.add(callback);
       },
+
+      // Optional property used by Scheduling Profiler:
+      displayName: `Inspecting ${element.displayName || 'Unknown'}`,
     };
+
     const wake = () => {
       // This assumes they won't throw.
       callbacks.forEach(callback => callback());

packages/react-reconciler/src/SchedulingProfiler.js

@@ -194,9 +194,16 @@ export function markComponentSuspended(
       const id = getWakeableID(wakeable);
       const componentName = getComponentNameFromFiber(fiber) || 'Unknown';
       const phase = fiber.alternate === null ? 'mount' : 'update';
+
+      // Following the non-standard fn.displayName convention,
+      // frameworks like Relay may also annotate Promises with a displayName,
+      // describing what operation/data the thrown Promise is related to.
+      // When this is available we should pass it along to the Scheduling Profiler.
+      const displayName = (wakeable: any).displayName || '';
+
       // TODO (scheduling profiler) Add component stack id
       markAndClear(
-        `--suspense-${eventType}-${id}-${componentName}-${phase}-${lanes}`,
+        `--suspense-${eventType}-${id}-${componentName}-${phase}-${lanes}-${displayName}`,
       );
       wakeable.then(
         () => markAndClear(`--suspense-resolved-${id}-${componentName}`),