Expo SDK 52: Fixing "Unable to Convert String to Floating Point Value" Error

Problem Statement

After upgrading to Expo SDK 52, developers may encounter the following runtime error:

(NOBRIDGE) ERROR Error: Exception in HostFunction: 
Unable to convert string to floating point value: "large"

This error indicates a type mismatch in style properties where numerical values are expected but string values are being supplied. The specific string triggering the error ("large" in this case) points to style declarations that violate React Native's strict typing requirements added in SDK 52.

Common characteristics:

• Occurs immediately after upgrading to Expo SDK 52
• Triggers during app runtime, often when rendering components
• Typically originates from problematic third-party libraries
• Most commonly affects style properties needing numerical values (fontSize, padding, margin, etc.)

Recommended Solutions

1. Identify and Update Problematic Libraries (Most Common Fix)

The most frequent cause is outdated libraries using string values for style properties. Here's how to resolve it:

# Step 1: Identify problematic libraries
npx expo doctor

# Step 2: Update all dependencies
npx expo install --fix

# Step 3: If specific library is known (e.g., date picker)
npm uninstall react-native-date-picker
npm install react-native-date-picker@latest

# For npm
rm -rf node_modules package-lock.json
npm install

# For Yarn
rm -rf node_modules yarn.lock
yarn install

Pro Tip: If you suspect a specific library but can't identify it, temporarily remove recently updated libraries one-by-one to isolate the culprit.

2. Locate and Fix Invalid Style Properties

Debug styles in your codebase using these techniques:

// SEARCH YOUR CODEBASE FOR:
// Any style property using the string "large"
<Text style={{ fontSize: 'large' }} /> // ❌ Problematic

// CORRECTED VERSION:
<Text style={{ fontSize: 16 }} />      // ✅ Numerical value

Debugging methods:

1. Global search for pattern : ['"]large['"]
2. Check these common properties:
   • fontSize
   • padding
   • margin
   • borderWidth
   • borderRadius
   • width/height

3. Validate Third-Party Library Styling

For libraries you can't update, implement runtime fixes:

// Create a style fixer component
const SafeStyledComponent = (Component) => (props) => {
  const sanitizedStyle = Object.entries(props.style || {}).reduce(
    (acc, [key, value]) => {
      acc[key] = typeof value === 'string' ? parseFloat(value) || 0 : value;
      return acc;
    }, 
    {}
  );

  return <Component {...props} style={sanitizedStyle} />;
};

// Usage: Wrap the problematic component
import { BuggyDatePicker } from 'problematic-library';
const FixedDatePicker = SafeStyledComponent(BuggyDatePicker);

4. Verify Custom Font Configuration

If using custom fonts where fontWeight might be set to "large":

// Replace non-numeric font weights
// Before (incorrect)
const styles = StyleSheet.create({
  title: {
    fontFamily: 'CustomFont',
    fontWeight: 'large'  // ❌ Invalid
  }
});

// After (correct)
const styles = StyleSheet.create({
  title: {
    fontFamily: 'CustomFont',
    fontWeight: '700'    // ✅ Numeric string (700 = bold)
  }
});

Preventative Measures

1. Upgrade Strategically: Always check library compatibility before SDK updates:

   expo install react-native@0.71.X # Match SDK 52 requirements

2. Enable Strict Type Checking: Add TypeScript or PropTypes validation:

   interface TextProps {
     size?: number; // Enforce numeric values
   }

3. Validate Styles During Build: Use ESLint rules to catch string values:

   // .eslintrc.json
   "rules": {
     "react-native/no-invalid-styles": "error"
   }

Conclusion

The "Unable to convert string to floating point value" error in Expo SDK 52 occurs when numerical style properties receive string values. The solution involves:

1. Updating problematic libraries (date pickers are frequent offenders)
2. Converting string style values to numbers ('large' → 16)
3. Sanitizing third-party component styles when needed
4. Implementing better type validation for styles

Prioritize library updates as they're the most common fix, then systematically audit style properties if errors persist. The stricter typing in modern Expo SDKs prevents runtime crashes when properly addressed.