[HOLD for payment 2023-12-29] [HOLD for payment 2023-12-28] Sign up - App crashes when signing up with a new account via magic link

[kbecciv]

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Version Number: v1.4.14-2
Reproducible in staging?: y
Reproducible in production?: n
If this was caught during regression testing, add the test name, ID and link from TestRail:
Email or phone of affected tester (no customers):
Logs: https://stackoverflow.com/c/expensify/questions/4856
Expensify/Expensify Issue URL:
Issue reported by: Applause - Internal Team
Slack conversation:

Action Performed:

Precondition: App must be freshly installed, or clear app data before running the steps below.

1. Launch New Expensify app.
2. Enter a new email account.
3. On magic code page, navigate to email and tap on the magic link.

Expected Result:

App does not crash.

Actual Result:

App crashes.

Workaround:

Unknown

Platforms:

Which of our officially supported platforms is this issue occurring on?

• Android: Native
• Android: mWeb Chrome
• iOS: Native
• iOS: mWeb Safari
• MacOS: Chrome / Safari
• MacOS: Desktop

Screenshots/Videos

Add any screenshot/video evidence

Bug6321189_1703076281038.Screen_Recording_20231220_193139_One_UI_Home__1_.mp4

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[github-actions]

👋 Friendly reminder that deploy blockers are time-sensitive ⏱ issues! Check out the open `StagingDeployCash` deploy checklist to see the list of PRs included in this release, then work quickly to do one of the following:

1. Identify the pull request that introduced this issue and revert it.
2. Find someone who can quickly fix the issue.
3. Fix the issue yourself.

[melvin-bot]

Triggered auto assignment to @puneetlath (Engineering), see https://stackoverflow.com/c/expensify/questions/4319 for more details.

[kbecciv]

Not reproducible in production

Screen_Recording_20231220_193915_New.Expensify.mp4

[ikevin127]

I can reproduce it with 100% success rate on local with latest main performing the following actions:

Precondition: App must be killed / closed (not opened in background) before running the steps below.

1. Launch New Expensify app.
2. Enter email account and tap Continue.
3. While on magic code page, navigate to your email and tap on the magic link.

Issue seems to be caused by the following line of code:

App/src/libs/Navigation/linkTo.ts

Line 83 in 9ea6b39

const topRouteName = rootState.routes.at(-1)?.name;

because the rootState.routes is undefined when attempting deep-link login first time the app is opened.

iOS: Native - Screenshot

The issue does not occur on subsequent trials if the app is not killed / closed and I think this is because subsequently the rootState.routes is not undefined anymore.

[mkhutornyi]

Proposal

Please re-state the problem that we are trying to solve in this issue.

Sign up - App crashes when signing up with a new account via magic link

What is the root cause of that problem?

This is regression from #32473

What changes do you think we should make in order to solve the problem?

Like old code, optional chaining should be added

[WojtekBoman]

Hello! Thank you for finding the cause of the problem :) I will add a fix in this PR which is also related to LHP #33359

[mkhutornyi]

The crash fix needs to be CPed. I don't think #33359 should be necessarily CPed.
Can we fix separately?