[NO QA][Sentry] Adding module names to web by elirangoshen · Pull Request #84422 · Expensify/App

elirangoshen · 2026-03-06T16:20:46Z

Explanation of Change

In production webpack builds, module IDs are numeric hashes (e.g. 535, 23042) instead of file paths. The Sentry breadcrumb for slow module init times was reporting these opaque numbers, making the data unusable
for identifying performance bottlenecks.

The changes:

ModuleInitTimingPlugin.ts — at build time, the plugin now iterates all webpack compilation modules and emits a self.__moduleNames = { "535": "./src/styles/index.ts", ... } runtime object mapping each numeric
ID to its relative source path. node_modules are excluded to keep the emitted JSON small.
index.web.ts — now reads __moduleNames (same typeof guard pattern used for __moduleInitTimes) and passes it to reportModuleInitTimes, which already uses it as a fallback: names?.[id] ?? id.

The native side (Metro) already had this via moduleInitPolyfill.ts + __moduleNames. This brings web to parity.

Fixed Issues

$#82975

Tests

Build the web app in production mode (npm run build)
Open the app, trigger some navigation to load modules
Open Sentry and inspect the module_init_times breadcrumb
Verify module entries now show readable paths like ./src/styles/index.ts instead of numeric IDs like 535
Verify the dev build still works (IDs are already paths in dev, __moduleNames is set but redundant — no regression)
Check bundle size has not grown significantly (names JSON is source-files only, no node_modules)

Verify that no errors appear in the JS console

Offline tests

N/A

QA Steps

N/A

Verify that no errors appear in the JS console

PR Author Checklist

Screenshots/Videos

Android: Native

Android: mWeb Chrome

iOS: Native

iOS: mWeb Safari

MacOS: Chrome / Safari

melvin-bot · 2026-03-06T16:21:27Z

@inimaga Please copy/paste the Reviewer Checklist from here into a new comment on this PR and complete it. If you have the K2 extension, you can simply click: [this button]

codecov · 2026-03-06T16:44:06Z

Codecov Report

✅ Changes either increased or maintained existing code coverage, great job!

Files with missing lines	Coverage Δ
src/setup/telemetry/index.web.ts	`0.00% <0.00%> (ø)`
... and 482 files with indirect coverage changes

inimaga · 2026-03-09T14:39:41Z

config/webpack/ModuleInitTimingPlugin.ts

+                // Build a moduleId → file path map so numeric production IDs are readable in Sentry.
+                // Skip node_modules to keep the emitted JSON small.
+                const names: Record<string, string> = {};
+                for (const module of compilation.modules) {


Hmmm. This is a going to add a non-trivial amount of startup JS for every user in production, as we're effectively shipping a moduleId -> path manifest for every first-party webpack module in the app inside the runtime chunk.
Could we rework this to avoid shipping the full map at startup? cc: @roryabraham

I wonder if we can solve this at build time instead of runtime (i.e: avoid mangling the module names in the first place)

We will do the JSON parsing for every user on startup, it might impact our app startup metrics negatively.
Eli do you think we are able to do it on build time rather than runtime?

I will check it and let you know

ok I changed it and now it should execute in build time, there one trade off which it need to execute 1 async action (fetch) but I think its minor effect. what do you think ? @roryabraham @inimaga

The map is now built at webpack compile time and written to a static file module-names.json in dist/. It never touches the runtime chunk. The app fetches it lazily inside requestAnimationFrame

I personally think a lazy fetch of a json file is probably a small price to pay for this visibility.

nit: why requestAnimationFrame instead of requestIdleCallback? The latter seems more idomatic for tasks unrelated to UI.

Sure I changed it and pushed other minor change due to an exception I had sometimes of Multiple assets emit different content to the same filename module-names.json. now it seems working good.

inimaga

One potential issue

roryabraham · 2026-03-09T22:07:39Z

@codex review

chatgpt-codex-connector · 2026-03-09T22:20:50Z

Codex Review: Didn't find any major issues. 🎉

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JmillsExpensify

No product review required on this one.

melvin-bot · 2026-03-10T21:26:06Z

Hey, I noticed you changed some webpack configuration files. This can break production builds. Did you remember to run a production build locally to verify they still work?

elirangoshen · 2026-03-11T07:07:07Z

I might refactor anyway so ill check after well decide what to do

Julesssss

@elirangoshen could you please share some before/after metrics for reference

elirangoshen · 2026-03-12T10:38:32Z

Hmmm. This is a going to add a non-trivial amount of startup JS for every user in production, as we're effectively shipping a moduleId -> path manifest for every first-party webpack module in the app inside the runtime chunk. Could we rework this to avoid shipping the full map at startup? cc: @roryabraham

so for the web span ManualAppStartup was better after the change , naybe due ti other chnages in main branch :
median value in 10 runs: ManualAppStartup duration was before the change1073ms and after 1016ms

src/setup/telemetry/index.web.ts

config/webpack/ModuleInitTimingPlugin.ts

Julesssss · 2026-03-19T17:48:44Z

@rinej @inimaga ready for our final reviews again.

src/setup/telemetry/index.web.ts

Julesssss

Looking good, one minor comment

Julesssss

LGTM

Julesssss · 2026-03-23T20:20:28Z

Sorry for delay, was ooo

Julesssss · 2026-03-23T20:21:24Z

Reviewer Checklist

I have verified the author checklist is complete (all boxes are checked off).
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Screenshots/Videos

Android: HybridApp

Android: mWeb Chrome

iOS: HybridApp

iOS: mWeb Safari

MacOS: Chrome / Safari

github-actions · 2026-03-23T20:47:10Z

🚧 @Julesssss has triggered a test Expensify/App build. You can view the workflow run here.

github-actions · 2026-03-23T20:51:54Z

🧪🧪 Use the links below to test this adhoc build on Android, iOS, and Web. Happy testing! 🧪🧪
Built from App PR #84422.

Android 🤖	iOS 🍎
https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-android-Adhoc-441d85a-5e0a0df-9b5c6f728af43adb6ec75b25df1695cdd03ee87e/index.html	https://ad-hoc-expensify-cash.s3.us-east-1.amazonaws.com/rock-artifacts/ad-hoc/rock-ios-device-AdHoc-441d85a-5e0a0df-be2aa42c05ada80ac516ecfca2e21e494d9afa07/index.html

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https://84422.pr-testing.expensify.com

👀 View the workflow run that generated this build 👀

OSBotify · 2026-03-25T16:09:47Z

🚀 Deployed to production by https://github.com/Julesssss in version: 9.3.43-3 🚀

platform	result
🕸 web 🕸	success ✅
🤖 android 🤖	success ✅
🍎 iOS 🍎	success ✅

adding module names to web

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elirangoshen requested review from a team as code owners March 6, 2026 16:20

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elirangoshen mentioned this pull request Mar 6, 2026

[Metrics] Improve App Start Time Performance #77171

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Julesssss changed the title ~~[Sentry] Adding module names to web~~ [NO QA][Sentry] Adding module names to web Mar 10, 2026

elirangoshen added 3 commits March 11, 2026 16:23

Merge branch 'main' into eliran/sentry-module-fix

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pr fix

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fix web error

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elirangoshen mentioned this pull request Mar 11, 2026

Add a span for measuring JS parse time #82975

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Investigate workflow job failing on main: chooseDeployActions #86138

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