TRLS013: Consider using GetValueOrDefault or Match

Cause

Using the ternary operator pattern result.IsSuccess ? result.Value : defaultValue when GetValueOrDefault() or Match() provides a more functional and safer alternative.

Rule Description

The pattern result.IsSuccess ? result.Value : defaultValue is verbose and can be replaced with more idiomatic functional methods:

GetValueOrDefault() for simple fallback values
Match() for transformations or side effects

How to Fix Violations

Option 1: Use GetValueOrDefault

// ❌ Verbose - Ternary operator
var customer = result.IsSuccess ? result.Value : defaultCustomer;

// ✅ Concise - GetValueOrDefault
var customer = result.GetValueOrDefault(defaultCustomer);

Option 2: Use Match

// ❌ Verbose - Ternary with transformation
var dto = result.IsSuccess ? result.Value.ToDto() : DefaultDto();

// ✅ Better - Match with transformation
var dto = result.Match(
    onSuccess: customer => customer.ToDto(),
    onFailure: _ => DefaultDto());

Examples

Example 1: Simple Fallback

// ❌ Ternary
var email = emailResult.IsSuccess 
    ? emailResult.Value 
    : EmailAddress.Create("noreply@example.com");

// ✅ GetValueOrDefault
var email = emailResult.GetValueOrDefault(
    EmailAddress.Create("noreply@example.com"));

Example 2: Fallback to Default Struct Value

// ❌ Ternary
var id = idResult.IsSuccess ? idResult.Value : Guid.Empty;

// ✅ GetValueOrDefault with default
var id = idResult.GetValueOrDefault();  // Uses default(Guid) = Guid.Empty

Example 3: With Transformation

// ❌ Ternary with transformation
var displayName = nameResult.IsSuccess 
    ? nameResult.Value.ToString() 
    : "Unknown";

// ✅ Match
var displayName = nameResult.Match(
    onSuccess: name => name.ToString(),
    onFailure: _ => "Unknown");

Example 4: Error-Dependent Fallback

// ❌ Can't easily access error details
var message = result.IsSuccess 
    ? "Success" 
    : "Failed";  // Lost error information

// ✅ Match with error details
var message = result.Match(
    onSuccess: _ => "Success",
    onFailure: error => $"Failed: {error.Detail}");

GetValueOrDefault Overloads

// Uses default(T) as fallback
result.GetValueOrDefault()

// Uses provided value as fallback
result.GetValueOrDefault(customDefault)

// Uses factory function as fallback (lazily evaluated)
result.GetValueOrDefault(() => CreateDefault())

Match Variants

// Match for transformations
var output = result.Match(
    onSuccess: value => TransformValue(value),
    onFailure: error => HandleError(error));

// Match for side effects (void return)
result.Match(
    onSuccess: value => Console.WriteLine(value),
    onFailure: error => Logger.LogError(error.Detail));

// MatchAsync for async transformations
var output = await result.MatchAsync(
    onSuccess: async value => await TransformAsync(value),
    onFailure: error => Task.FromResult(default));

Benefits

Null Safety

// ❌ Ternary - Can accidentally access Value on failure
var name = result.IsSuccess ? result.Value : defaultName;
// If you mistype IsFailure, you get an exception!

// ✅ GetValueOrDefault - Can't access Value incorrectly
var name = result.GetValueOrDefault(defaultName);

Functional Composition

// ✅ Chainable
return GetCustomer(id)
    .Match(
        onSuccess: customer => customer.Email,
        onFailure: _ => EmailAddress.Create("noreply@example.com"))
    .ToString();

When to Use Ternary

Use the ternary operator when:

You're checking other properties (not just IsSuccess)
The logic is complex and doesn't fit Match

// Ternary appropriate - checking different property
var count = list.Count > 0 ? list.Count : defaultCount;

When to Suppress Warnings

This is a suggestion-level diagnostic. Suppress it if:

You prefer explicit ternary operators for clarity
The pattern doesn't fit GetValueOrDefault or Match
You're working with legacy code

TRLS003 - Unsafe access to Result.Value

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