improve result structure and handling
This commit is contained in:
Oli Sturm
+13
-18
@@ -1,4 +1,5 @@
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using CsharpEs.Library;
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using static CsharpEs.Library.ResultModule;
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namespace CsharpEs.Domain;
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@@ -47,31 +48,27 @@ public static class AccountDecider
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(state, command) switch
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{
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// if this is a new account, check for valid opening balance
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(null, AccountCommand.OpenAccount c) when c.OpeningBalance.Amount < 0m =>
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Result<AccountEvent, AccountError>.Fail(
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new AccountError.OpeningBalanceMustBeNonNegative()
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),
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(null, AccountCommand.OpenAccount c) when c.OpeningBalance.Amount < 0m => Fail(
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new AccountError.OpeningBalanceMustBeNonNegative()
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),
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// still a new account, now we can open it
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(null, AccountCommand.OpenAccount c) => Result<AccountEvent, AccountError>.Ok(
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(null, AccountCommand.OpenAccount c) => Ok(
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new AccountEvent.AccountOpened(c.AccountId, c.OpeningBalance)
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),
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// if we have an account already, you can't open it
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(not null, AccountCommand.OpenAccount c) => Result<
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AccountEvent,
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AccountError
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>.Fail(new AccountError.AccountOpenAlready()),
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(null, _) => Result<AccountEvent, AccountError>.Fail(
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new AccountError.AccountNotFound()
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(not null, AccountCommand.OpenAccount c) => Fail(
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new AccountError.AccountOpenAlready()
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),
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(_, AccountCommand.WithdrawMoney c) => Result<AccountEvent, AccountError>.Ok(
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(null, _) => Fail(new AccountError.AccountNotFound()),
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(_, AccountCommand.WithdrawMoney c) => Ok(
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new AccountEvent.MoneyWithdrawn(c.AccountId, c.Amount)
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),
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(_, AccountCommand.DepositMoney c) => Result<AccountEvent, AccountError>.Ok(
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(_, AccountCommand.DepositMoney c) => Ok(
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new AccountEvent.MoneyDeposited(c.AccountId, c.Amount)
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),
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@@ -86,10 +83,8 @@ public static class AccountDecider
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) =>
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(state, @event) switch
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{
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(null, AccountEvent.AccountOpened e) => Result<AccountState?, AccountError>.Ok(
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new AccountState(e.AccountId)
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),
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(null, AccountEvent.AccountOpened e) => Ok(new AccountState(e.AccountId)),
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_ => Result<AccountState?, AccountError>.Ok(state),
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_ => Ok(state),
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};
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}
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@@ -1,6 +1,7 @@
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using System.Collections.Immutable;
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using CsharpEs.Domain;
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using CsharpEs.Library;
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using static CsharpEs.Library.ResultModule;
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namespace CsharpEs.Infrastructure;
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@@ -57,9 +58,7 @@ public static class AccountBalanceReadModelModule
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);
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}
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else
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return Result<AccountDetails, ReadModelError>.Fail(
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new ReadModelError.AccountDetailsNotFound()
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);
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return Fail(new ReadModelError.AccountDetailsNotFound());
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}
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break;
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@@ -78,9 +77,7 @@ public static class AccountBalanceReadModelModule
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);
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}
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else
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return Result<AccountDetails, ReadModelError>.Fail(
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new ReadModelError.AccountDetailsNotFound()
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);
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return Fail(new ReadModelError.AccountDetailsNotFound());
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}
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break;
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}
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@@ -88,15 +85,13 @@ public static class AccountBalanceReadModelModule
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// Read model-side "project" may not normally return any data, but for demo
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// purposes we return the affected data directly to save us modeling a separate
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// query side.
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return Result<AccountDetails, ReadModelError>.Ok(modelData[@event.AccountId]);
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return Ok(modelData[@event.AccountId]);
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}
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Result<KeyValuePair<Guid, AccountDetails>[], ReadModelError> Query() =>
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Result<KeyValuePair<Guid, AccountDetails>[], ReadModelError>.Ok(modelData.ToArray());
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Ok(modelData.ToArray());
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return Result<AccountBalanceReadModel, ReadModelError>.Ok(
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new AccountBalanceReadModel(Project, Query)
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);
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return Ok(new AccountBalanceReadModel(Project, Query));
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}
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private static AccountFlags CalcAccountFlags(Money newBalance, AccountDetails oldDetails)
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+116
-117
@@ -1,138 +1,137 @@
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namespace CsharpEs.Library;
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public readonly record struct Result<T, E>
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// disable match exhaustion warnings - C# thinks we could have other
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// derived instances of Result<T,E> but there's no way to say
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// "don't allow creation of further derived types" while leaving
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// the type publicly visible.
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#pragma warning disable CS8509
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public abstract record Result<T, E>
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{
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private readonly T _value;
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public static implicit operator Result<T, E>(T value) => new ResultOk<T, E>(value);
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private readonly E _error;
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public static implicit operator Result<T, E>(E error) => new ResultFail<T, E>(error);
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}
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public bool IsSuccess { get; }
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public sealed record ResultOk<T, E>(T Value) : Result<T, E>;
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public bool IsFailure => !IsSuccess;
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public sealed record ResultFail<T, E>(E Error) : Result<T, E>;
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public T Value =>
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IsSuccess
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? _value
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: throw new InvalidOperationException("No value present for failed result.");
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public static class ResultModule
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{
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public static T Ok<T>(T v) => v;
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public E Error =>
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IsFailure
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? _error
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: throw new InvalidOperationException("No error present for successful result.");
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public static Result<T?, E> OkNone<T, E>()
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where T : class? => new ResultOk<T?, E>(null);
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private Result(T value)
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{
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_value = value;
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_error = default!;
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IsSuccess = true;
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}
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private Result(E error)
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{
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_value = default!;
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_error = error;
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IsSuccess = false;
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}
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public static Result<T, E> Ok(T value) => new(value);
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public static Result<T, E> Fail(E error) => new(error);
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public TResult Match<TResult>(Func<T, TResult> onSuccess, Func<E, TResult> onFailure) =>
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IsSuccess ? onSuccess(_value) : onFailure(_error);
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public void Switch(Action<T> onSuccess, Action<E> onFailure)
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{
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if (IsSuccess)
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onSuccess(_value);
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else
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onFailure(_error);
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}
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public static Result<T, E> Catch(Func<T> f, Func<Exception, E> exceptionMapper)
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{
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try
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{
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var result = f();
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return Result<T, E>.Ok(result);
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}
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catch (Exception e)
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{
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return Result<T, E>.Fail(exceptionMapper(e));
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}
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}
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public static Result<T, E> Catch(Func<Result<T, E>> f, Func<Exception, E> exceptionMapper)
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{
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try
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{
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return f();
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}
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catch (Exception e)
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{
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return Result<T, E>.Fail(exceptionMapper(e));
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}
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}
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public static E Fail<E>(E e) => e;
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}
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public static class ResultExtensions
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{
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public static Result<TOut, E> Bind<TIn, TOut, E>(
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this Result<TIn, E> result,
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Func<TIn, Result<TOut, E>> binder
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) => result.IsSuccess ? binder(result.Value) : Result<TOut, E>.Fail(result.Error);
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public static Result<TOut, E> Map<TIn, TOut, E>(
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this Result<TIn, E> result,
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Func<TIn, TOut> mapper
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) =>
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result.IsSuccess
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? Result<TOut, E>.Ok(mapper(result.Value))
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: Result<TOut, E>.Fail(result.Error);
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public static Result<T, E> Tap<T, E>(this Result<T, E> result, Action<T> action)
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extension<TIn, E>(Result<TIn, E> result)
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{
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if (result.IsSuccess)
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action(result.Value);
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public bool IsSuccess => result is ResultOk<TIn, E>;
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public bool IsFailure => !result.IsSuccess;
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return result;
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public Result<TOut, E> Bind<TOut>(Func<TIn, Result<TOut, E>> binder) =>
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result switch
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{
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ResultOk<TIn, E>(var v) => binder(v),
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ResultFail<TIn, E>(var e) => new ResultFail<TOut, E>(e),
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};
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public Result<TOut, E> Map<TOut>(Func<TIn, TOut> mapper) =>
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result switch
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{
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ResultOk<TIn, E>(var v) => new ResultOk<TOut, E>(mapper(v)),
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ResultFail<TIn, E>(var e) => new ResultFail<TOut, E>(e),
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};
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public Result<TIn, EOut> MapError<EOut>(Func<E, EOut> mapper) =>
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result switch
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{
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ResultOk<TIn, E>(var v) => new ResultOk<TIn, EOut>(v),
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ResultFail<TIn, E>(var e) => new ResultFail<TIn, EOut>(mapper(e)),
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};
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public Result<TIn, E> Tap(Action<TIn> action)
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{
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if (result is ResultOk<TIn, E>(var v))
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action(v);
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return result;
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}
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public Result<TIn, E> TapError(Action<E> action)
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{
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if (result is ResultFail<TIn, E>(var e))
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action(e);
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return result;
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}
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public Result<TIn, E> Log(string src, string msg) =>
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Tap(result, Logging.OutputDelegate<TIn>(src, msg))
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.TapError(m => Logging.OutputError(src, m));
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public Result<TIn, E> Log(string src, Func<TIn, string> renderText) =>
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Tap(result, x => Logging.OutputDelegate<TIn>(src, renderText(x))(x))
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.TapError(m => Logging.OutputError(src, m));
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public Result<TOut, E> Select<TOut>(Func<TIn, TOut> mapper) => Map(result, mapper);
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public Result<TOut, E> SelectMany<TIntermediate, TOut>(
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Func<TIn, Result<TIntermediate, E>> binder,
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Func<TIn, TIntermediate, TOut> projector
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) => Bind(result, x => binder(x).Map(y => projector(x, y)));
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public TResult Match<TResult>(Func<TIn, TResult> onSuccess, Func<E, TResult> onFailure) =>
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result switch
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{
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ResultOk<TIn, E>(var v) => onSuccess(v),
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ResultFail<TIn, E>(var e) => onFailure(e),
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};
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public void Switch(Action<TIn> onSuccess, Action<E> onFailure)
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{
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switch (result)
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{
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case ResultOk<TIn, E>(var v):
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onSuccess(v);
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break;
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case ResultFail<TIn, E>(var e):
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onFailure(e);
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break;
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}
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}
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}
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public static Result<T, E> TapError<T, E>(this Result<T, E> result, Action<E> action)
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extension<TIn, E>(Result<TIn, E>)
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{
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if (result.IsFailure)
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action(result.Error);
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public static Result<TIn, E> Catch(Func<TIn> f, Func<Exception, E> exceptionMapper)
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{
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try
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{
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return new ResultOk<TIn, E>(f());
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}
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catch (Exception e)
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{
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return new ResultFail<TIn, E>(exceptionMapper(e));
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}
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}
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return result;
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public static Result<TIn, E> Catch(
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Func<Result<TIn, E>> f,
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Func<Exception, E> exceptionMapper
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)
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{
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try
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{
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return f();
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}
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catch (Exception e)
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{
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return new ResultFail<TIn, E>(exceptionMapper(e));
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}
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}
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}
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public static Result<T, EOut> MapError<T, EIn, EOut>(
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this Result<T, EIn> result,
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Func<EIn, EOut> map
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) =>
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result.IsSuccess
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? Result<T, EOut>.Ok(result.Value)
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: Result<T, EOut>.Fail(map(result.Error));
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public static Result<T, E> Log<T, E>(this Result<T, E> result, string src, string msg) =>
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Tap(result, Logging.OutputDelegate<T>(src, msg)).TapError(m => Logging.OutputError(src, m));
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public static Result<T, E> Log<T, E>(
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this Result<T, E> result,
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string src,
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Func<T, string> renderText
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) =>
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Tap(result, x => Logging.OutputDelegate<T>(src, renderText(x))(x))
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.TapError(m => Logging.OutputError(src, m));
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public static Result<TOut, E> Select<TIn, TOut, E>(
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this Result<TIn, E> result,
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Func<TIn, TOut> mapper
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) => result.Map(mapper);
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public static Result<TOut, E> SelectMany<TIn, TIntermediate, TOut, E>(
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this Result<TIn, E> result,
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Func<TIn, Result<TIntermediate, E>> binder,
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Func<TIn, TIntermediate, TOut> projector
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) => result.Bind(x => binder(x).Map(y => projector(x, y)));
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}
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@@ -2,6 +2,7 @@
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using CsharpEs.Domain;
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using CsharpEs.Infrastructure;
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using CsharpEs.Library;
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using static CsharpEs.Library.ResultModule;
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public abstract record DemoError
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{
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@@ -66,7 +67,7 @@ public class Program
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.Bind(readModel =>
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demoCommands
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.Aggregate(
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Result<AccountState?, DemoError>.Ok(null),
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OkNone<AccountState?, DemoError>(),
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(stateResult, command) =>
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stateResult
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.Bind(state =>
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