fix: prevent "NaN" market cap in watchlist when Finnhub omits the value

[Mubashirrrr]

Bug

The watchlist table renders the literal string NaN in the Market Cap column for any stock whose market cap is unavailable.

formatNumber (lib/utils.ts) computes num * 1e6 and formats the result. But getWatchlistData (lib/actions/finnhub.actions.ts) passes the value straight through:

marketCap: profile?.marketCapitalization,   // number | undefined

Finnhub's /stock/profile2 endpoint omits marketCapitalization for many symbols (ETFs and a lot of non-US tickers). When it's missing, formatNumber(undefined) evaluates undefined * 1e6 → NaN, falls through every value >= … branch, and returns NaN.toString() → "NaN", which WatchlistTable.tsx renders directly:

<td className="px-6 py-4 text-gray-400 font-medium">
    {formatNumber(stock.marketCap)}
</td>

Reproduction

formatNumber(undefined) // => "NaN"  (rendered in the Market Cap cell)
formatNumber(NaN)       // => "NaN"

The included regression test asserts this and fails before the fix:

AssertionError: expected 'NaN' to be 'N/A'

Fix

Guard against undefined / null / non-finite input and return 'N/A' — the same convention already used by the sibling helper formatMarketCapValue. The parameter type is widened to number | null | undefined to reflect what actually reaches the function on the watchlist call path. No other behavior changes; the existing millions-scaling logic is untouched.

Regression test

Added a formatNumber block to __tests__/utils.test.ts covering:

• the normal millions-scaled path (3_000_000 → "3.00T", 150_000 → "150.00B", 150 → "150.00M")
• the missing / non-finite path (undefined, null, NaN, Infinity → "N/A")

npm test is green (81 passed, 4 pre-existing skips). Confirmed the new test fails before the fix and passes after.

Summary by CodeRabbit

• Bug Fixes
  • Improved number formatting to gracefully handle missing, null, or invalid market data by displaying "N/A" instead of potential errors, ensuring more stable and reliable data presentation throughout the application.

[vercel]

@Mubashirrrr is attempting to deploy a commit to the ravixalgorithm's projects Team on Vercel.

A member of the Team first needs to authorize it.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c03993eb-4389-4f29-bf90-1a4f45e027d4

📥 Commits

Reviewing files that changed from the base of the PR and between 8326133 and dd6afc8.

📒 Files selected for processing (2)

• __tests__/utils.test.ts
• lib/utils.ts

---

📝 Walkthrough

Walkthrough

The formatNumber utility function is enhanced to handle edge cases by accepting optional or nullable inputs and returning 'N/A' for undefined, null, or non-finite values. A comprehensive test suite validates the updated behavior, including formatting market-cap values in millions to suffixes (T, B, M) and error cases.

Changes

formatNumber Input Validation

Layer / File(s)	Summary
formatNumber robustness update lib/utils.ts, __tests__/utils.test.ts	formatNumber signature widens to accept num?: number | null and returns 'N/A' for invalid inputs. Tests verify suffix formatting for millions (→M), billions (→B), trillions (→T) and error handling for undefined, null, NaN, and Infinity.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A number walks in, could be null or divine,
formatNumber asks: "Are you finite and fine?"
If not, it returns a sweet 'N/A' reply,
While tests keep watch—no edge case to defy!
✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main fix: preventing 'NaN' display in market cap when Finnhub omits the value. It is specific, concise, and directly reflects the core change.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands and usage tips.}