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Validate nullability with types

microsoft/vscode
Based on 10 comments
Typescript

Always handle null and undefined values explicitly through proper type declarations and validation patterns rather than using non-null assertions or unsafe type casts. This ensures type safety and prevents runtime errors.

Null Handling Typescript

Reviewer Prompt

Always handle null and undefined values explicitly through proper type declarations and validation patterns rather than using non-null assertions or unsafe type casts. This ensures type safety and prevents runtime errors.

Key practices:

  1. Use type declarations to make nullability explicit
  2. Implement proper validation before accessing potentially null values
  3. Prefer assignment patterns over non-null assertions
  4. Use type-safe alternatives like optional chaining and nullish coalescing

Example:

// ❌ Avoid
function processItem(item: Item | undefined) {
    return item!.value; // Unsafe non-null assertion
}

// ✅ Better
function processItem(item: Item | undefined) {
    if (!item) {
        return undefined;
    }
    return item.value;
}

// ✅ Even better - using type guards
function processItem(item: Item | undefined): string | undefined {
    if (isValidItem(item)) {
        return item.value;
    }
    return undefined;
}

// ✅ Best - with proper typing and validation
interface ItemProcessor {
    process(item: Item): string;
}

class SafeItemProcessor implements ItemProcessor {
    process(item: Item): string {
        // Type system ensures item is never null/undefined
        return item.value;
    }
}
10
Comments Analyzed
Typescript
Primary Language
Null Handling
Category

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