[react-native-app] ProductCard shows wrong price, nanos divided by 1e8 instead of 1e9

[bhuvan-somisetty]

Bug Report

Commit 92df8a2 (main).

Symptom

ProductCard in src/react-native-app/components/ProductCard/ProductCard.tsx converts a product's Money price to a display string like this:

const price = (priceUsd?.units + priceUsd?.nanos / 100000000).toFixed(2);

Per src/react-native-app/protos/demo.ts, nanos is documented as nano (10^-9) units of the amount, e.g. $-1.75 is represented as units=-1, nanos=-750,000,000. Converting nanos back to a fractional dollar amount requires dividing by 1,000,000,000 (1e9), not 100,000,000 (1e8). The divisor here is off by a factor of 10.

The frontend web app does this correctly in src/frontend/components/ProductPrice/ProductPrice.tsx (units + nanos / 1000000000), the react-native-app's ProductCard.tsx even has a comment at the top saying it was "Copied with modification from src/frontend/components/ProductCard/ProductCard.tsx", the modification appears to be where the wrong divisor was introduced.

What is the expected behavior?

The price shown on the product card should match the actual Money value, e.g. a product priced at units=24, nanos=990000000 ($24.99) should render as $ 24.99.

What is the actual behavior?

The fractional part of the price is inflated by 10x. For units=24, nanos=990000000:

24 + 990000000 / 100000000 = 24 + 9.9 = 33.90

so the card shows $ 33.90 instead of $ 24.99.

Reproduce

1. Run the react-native-app against the demo backend (or just read ProductCard.tsx line 49 alongside any Money value where nanos is non-zero).
2. Look at any product card's displayed price.
3. Compare to the same product's price shown in the web frontend, the react-native price will be inflated whenever the product's cents aren't .00.

Additional Context

Same class of bug as #3742 and #3747 (mishandling the Money.nanos field), this time in a price shown directly to the user rather than in telemetry. nanos needs to be divided by 1_000_000_000, not 100_000_000.

Component(s)

react-native-app