From 919c4a0aeb0cc99fe72a1a4d64b3587efcf1aa47 Mon Sep 17 00:00:00 2001
From: Joel Mueller <joel.mueller@gmail.com>
Date: Tue, 21 May 2024 22:25:36 -0500
Subject: [PATCH] CopyValuesTo and CopyErrorsTo for Result

---
 .../Async/ResultAsyncExtensions.cs            |   4 +
 src/RustyOptions/NumericOptionExtensions.cs   |  15 +-
 .../OptionCollectionExtensions.cs             |  20 ++-
 .../ResultCollectionExtensions.cs             | 166 +++++++++++++++++-
 4 files changed, 185 insertions(+), 20 deletions(-)

diff --git a/src/RustyOptions/Async/ResultAsyncExtensions.cs b/src/RustyOptions/Async/ResultAsyncExtensions.cs
index ca79276..46655f9 100644
--- a/src/RustyOptions/Async/ResultAsyncExtensions.cs
+++ b/src/RustyOptions/Async/ResultAsyncExtensions.cs
@@ -731,6 +731,10 @@ public static async ValueTask<Result<T, T2Err>> OrElseAsync<T, T1Err, T2Err>(thi
         return Result.Ok<T, T2Err>(result.Unwrap());
     }
 
+    // NOTE: Due to a bug in coverlet.collector, certain lines in methods involving IAsyncEnumerable
+    // will show as partially-covered in code-coverage tools, even when they are fully-covered.
+    // https://github.com/coverlet-coverage/coverlet/issues/1104#issuecomment-1005332269
+
     /// <summary>
     /// Flattens an asynchronous sequence of <see cref="Result{T, TErr}"/> into a sequence containing all inner values.
     /// Error results are discarded.
diff --git a/src/RustyOptions/NumericOptionExtensions.cs b/src/RustyOptions/NumericOptionExtensions.cs
index df53773..5790ed1 100644
--- a/src/RustyOptions/NumericOptionExtensions.cs
+++ b/src/RustyOptions/NumericOptionExtensions.cs
@@ -267,8 +267,9 @@ public static IEnumerable<T> Values<T>(this IEnumerable<NumericOption<T>> self)
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="NumericOption{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="NumericOption{T}"/> in an array
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
@@ -285,8 +286,9 @@ public static Span<T> CopyValuesTo<T>(this NumericOption<T>[] self, Span<T> dest
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="NumericOption{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="NumericOption{T}"/> in a list
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
@@ -303,8 +305,9 @@ public static Span<T> CopyValuesTo<T>(this List<NumericOption<T>> self, Span<T>
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="NumericOption{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="NumericOption{T}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
diff --git a/src/RustyOptions/OptionCollectionExtensions.cs b/src/RustyOptions/OptionCollectionExtensions.cs
index 5c019fb..ea97f36 100644
--- a/src/RustyOptions/OptionCollectionExtensions.cs
+++ b/src/RustyOptions/OptionCollectionExtensions.cs
@@ -40,8 +40,9 @@ public static IEnumerable<T> Values<T>(this IEnumerable<Option<T>> self)
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="Option{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="Option{T}"/> in an array 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
@@ -58,8 +59,9 @@ public static Span<T> CopyValuesTo<T>(this Option<T>[] self, Span<T> destination
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="Option{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="Option{T}"/> in a List 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
@@ -76,8 +78,9 @@ public static Span<T> CopyValuesTo<T>(this List<Option<T>> self, Span<T> destina
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="Option{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="Option{T}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
@@ -94,8 +97,9 @@ public static Span<T> CopyValuesTo<T>(this Span<Option<T>> self, Span<T> destina
     }
 
     /// <summary>
-    /// Copies the inner values of all <see cref="Option{T}"/> in a span to a <paramref name="destination"/> span,
-    /// returning the destination span trimmed to the number of values copied.
+    /// Copies the inner values of all <see cref="Option{T}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied.
     /// </summary>
     /// <typeparam name="T">The type of the numeric option values.</typeparam>
     /// <param name="self">The source span of numeric options.</param>
diff --git a/src/RustyOptions/ResultCollectionExtensions.cs b/src/RustyOptions/ResultCollectionExtensions.cs
index 91650fc..2f2d4d9 100644
--- a/src/RustyOptions/ResultCollectionExtensions.cs
+++ b/src/RustyOptions/ResultCollectionExtensions.cs
@@ -1,4 +1,6 @@
-using static System.ArgumentNullException;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using static System.ArgumentNullException;
 
 namespace RustyOptions;
 
@@ -7,10 +9,6 @@ namespace RustyOptions;
 /// </summary>
 public static class ResultCollectionExtensions
 {
-    // NOTE: Due to a bug in coverlet.collector, certain lines in methods involving IAsyncEnumerable
-    // will show as partially-covered in code-coverage tools, even when they are fully-covered.
-    // https://github.com/coverlet-coverage/coverlet/issues/1104#issuecomment-1005332269
-
     /// <summary>
     /// Flattens a sequence of <see cref="Result{T, TErr}"/> into a sequence containing all inner values.
     /// Error results are discarded.
@@ -32,7 +30,84 @@ public static IEnumerable<T> Values<T, TErr>(this IEnumerable<Result<T, TErr>> s
         }
     }
 
-    // TODO: Span overload for Values?
+    /// <summary>
+    /// Copies the inner values of all <see cref="Result{T, TErr}"/> in an array 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the values to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the values.
+    /// </exception>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Span<T> CopyValuesTo<T, TErr>(this Result<T, TErr>[] self, Span<T> destination)
+        where T : notnull
+    {
+        return CopyValuesTo((ReadOnlySpan<Result<T, TErr>>)self, destination);
+    }
+
+    /// <summary>
+    /// Copies the inner values of all <see cref="Result{T, TErr}"/> in a List 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the values to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the values.
+    /// </exception>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Span<T> CopyValuesTo<T, TErr>(this List<Result<T, TErr>> self, Span<T> destination)
+        where T : notnull
+    {
+        return CollectionsMarshal.AsSpan(self).CopyValuesTo(destination);
+    }
+
+    /// <summary>
+    /// Copies the inner values of all <see cref="Result{T, TErr}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the values to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the values.
+    /// </exception>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Span<T> CopyValuesTo<T, TErr>(this Span<Result<T, TErr>> self, Span<T> destination)
+        where T : notnull
+    {
+        return CopyValuesTo((ReadOnlySpan<Result<T, TErr>>)self, destination);
+    }
+
+    /// <summary>
+    /// Copies the inner values of all <see cref="Result{T, TErr}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the values to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the values.
+    /// </exception>
+    public static Span<T> CopyValuesTo<T, TErr>(this ReadOnlySpan<Result<T, TErr>> self, Span<T> destination)
+        where T : notnull
+    {
+        int j = 0;
+        for (int i = 0; i < self.Length; i++)
+        {
+            if (self[i].IsOk(out var value))
+            {
+                destination[j++] = value;
+            }
+        }
+        return destination[..j];
+    }
 
     /// <summary>
     /// Flattens a sequence of <see cref="Result{T, TErr}"/> into a sequence containing all error values.
@@ -54,4 +129,83 @@ public static IEnumerable<TErr> Errors<T, TErr>(this IEnumerable<Result<T, TErr>
             }
         }
     }
+
+    /// <summary>
+    /// Copies the error values of all <see cref="Result{T, TErr}"/> in an array 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the errors to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the errors.
+    /// </exception>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Span<TErr> CopyErrorssTo<T, TErr>(this Result<T, TErr>[] self, Span<TErr> destination)
+        where T : notnull
+    {
+        return CopyErrorsTo((ReadOnlySpan<Result<T, TErr>>)self, destination);
+    }
+
+    /// <summary>
+    /// Copies the error values of all <see cref="Result{T, TErr}"/> in a List 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the errors to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the errors.
+    /// </exception>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Span<TErr> CopyErrorsTo<T, TErr>(this List<Result<T, TErr>> self, Span<TErr> destination)
+        where T : notnull
+    {
+        return CollectionsMarshal.AsSpan(self).CopyErrorsTo(destination);
+    }
+
+    /// <summary>
+    /// Copies the error values of all <see cref="Result{T, TErr}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the errors to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the errors.
+    /// </exception>
+    [MethodImpl(MethodImplOptions.AggressiveInlining)]
+    public static Span<TErr> CopyErrorsTo<T, TErr>(this Span<Result<T, TErr>> self, Span<TErr> destination)
+        where T : notnull
+    {
+        return CopyErrorsTo((ReadOnlySpan<Result<T, TErr>>)self, destination);
+    }
+
+    /// <summary>
+    /// Copies the error values of all <see cref="Result{T, TErr}"/> in a span 
+    /// to a <paramref name="destination"/> span, returning the destination span 
+    /// trimmed to the number of values copied. Error results are discarded.
+    /// </summary>
+    /// <param name="self">The source span of results.</param>
+    /// <param name="destination">The destination span to copy the errors to.</param>
+    /// <returns>A flattened sequence of values.</returns>
+    /// <exception cref="System.IndexOutOfRangeException">
+    /// Thrown if the destination span is too small to hold all the errors.
+    /// </exception>
+    public static Span<TErr> CopyErrorsTo<T, TErr>(this ReadOnlySpan<Result<T, TErr>> self, Span<TErr> destination)
+        where T : notnull
+    {
+        int j = 0;
+        for (int i = 0; i < self.Length; i++)
+        {
+            if (self[i].IsErr(out var err) && err is not null)
+            {
+                destination[j++] = err;
+            }
+        }
+        return destination[..j];
+    }
 }