MrDevRobot.ErrorOr.Extensions 1.0.0

MrDevRobot.ErrorOr.Extensions

Extension methods for the ErrorOr library, adding ValueTask support, functional aliases (Map/Bind), and Combine/Collect for error aggregation.

Installation

dotnet add package MrDevRobot.ErrorOr.Extensions

The package targets netstandard2.0 and net8.0, so it works with .NET Framework 4.6.1+, .NET Core 2.0+, and .NET 5+.

The namespace is ErrorOr — the same as the base library. No additional using directives needed.

Features

1. ValueTask Support

Full ValueTask<ErrorOr<T>> support for all fluent operations, mirroring the existing Task<ErrorOr<T>> extensions.

Three categories of overloads are provided for each operation:

Operations covered: Then, ThenDo, ThenAsync, ThenDoAsync, Match, MatchFirst, MatchAsync, MatchFirstAsync, Switch, SwitchFirst, SwitchAsync, SwitchFirstAsync, Else, ElseAsync, FailIf, FailIfAsync.

Example — chaining with ValueTask

ValueTask<ErrorOr<User>> GetUserAsync(int id) => ...;
ValueTask<ErrorOr<Order>> GetLastOrderAsync(User user) => ...;

ErrorOr<decimal> result = await GetUserAsync(42)
    .ThenAsync(user => GetLastOrderAsync(user))
    .Then(order => order.Total);

Example — ValueTask callback on ErrorOr<T>

ErrorOr<int> errorOr = 42;

ErrorOr<string> result = await errorOr
    .ThenAsync(value => new ValueTask<string>(value.ToString()));

2. Functional Aliases — Map / Bind

Aliases for developers familiar with functional programming terminology:

All aliases are available on ErrorOr<T>, Task<ErrorOr<T>>, and ValueTask<ErrorOr<T>>.

Example

ErrorOr<string> name = "Alice";

ErrorOr<int> length = name.Map(n => n.Length);

ErrorOr<User> user = name.Bind(n => FindUser(n)); // FindUser returns ErrorOr<User>

3. Combine / Collect — Error Aggregation

Aggregate multiple ErrorOr<T> results, collecting all errors instead of short-circuiting at the first failure.

Combine — heterogeneous types

Merge 2–6 ErrorOr<T> of different types into a named tuple:

ErrorOr<string> nameResult = ValidateName(input.Name);
ErrorOr<int> ageResult = ValidateAge(input.Age);
ErrorOr<string> emailResult = ValidateEmail(input.Email);

ErrorOr<(string First, int Second, string Third)> combined =
    nameResult.Combine(ageResult, emailResult);

// If all valid:
var (name, age, email) = combined.Value;

// If any failed: combined.Errors contains ALL validation errors

Collect — homogeneous type

Merge a sequence of ErrorOr<T> into a single ErrorOr<List<T>>:

var validations = new[]
{
    ValidateField("name", input.Name),
    ValidateField("email", input.Email),
    ValidateField("phone", input.Phone),
};

ErrorOr<List<string>> result = validations.Collect();
// result.Value is List<string> with all valid values
// result.Errors contains every error from every failed validation

API Reference

ValueTask Extensions (ErrorOrValueTaskExtensions)

Functional Aliases (ErrorOrMapBindExtensions)

Combine / Collect (ErrorOrCombineExtensions)

Compatibility

Depends on:

• ErrorOr ≥ 2.0.1
• System.Threading.Tasks.Extensions 4.5.4 (netstandard2.0 only)

License

This project is licensed under the MIT License.