Add Join/LeftJoin/RightJoin tuple overloads to LINQ APIs

src/libraries/System.Linq.AsyncEnumerable/ref/System.Linq.AsyncEnumerable.cs

@@ -81,6 +81,8 @@ public static partial class AsyncEnumerable
         public static System.Collections.Generic.IAsyncEnumerable<TSource> Intersect<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> first, System.Collections.Generic.IAsyncEnumerable<TSource> second, System.Collections.Generic.IEqualityComparer<TSource>? comparer = null) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> Join<TOuter, TInner, TKey, TResult>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> outerKeySelector, System.Func<TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> innerKeySelector, System.Func<TOuter, TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> Join<TOuter, TInner, TKey, TResult>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, TKey> outerKeySelector, System.Func<TInner, TKey> innerKeySelector, System.Func<TOuter, TInner, TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
+        public static System.Collections.Generic.IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> outerKeySelector, System.Func<TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> innerKeySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
+        public static System.Collections.Generic.IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, TKey> outerKeySelector, System.Func<TInner, TKey> innerKeySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
         public static System.Threading.Tasks.ValueTask<TSource> LastAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, bool> predicate, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Threading.Tasks.ValueTask<TSource> LastAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<bool>> predicate, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Threading.Tasks.ValueTask<TSource> LastAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
@@ -92,6 +94,8 @@ public static partial class AsyncEnumerable
         public static System.Threading.Tasks.ValueTask<TSource> LastOrDefaultAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, TSource defaultValue, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> LeftJoin<TOuter, TInner, TKey, TResult>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> outerKeySelector, System.Func<TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> innerKeySelector, System.Func<TOuter, TInner?, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> LeftJoin<TOuter, TInner, TKey, TResult>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, TKey> outerKeySelector, System.Func<TInner, TKey> innerKeySelector, System.Func<TOuter, TInner?, TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
+        public static System.Collections.Generic.IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> outerKeySelector, System.Func<TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> innerKeySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
+        public static System.Collections.Generic.IAsyncEnumerable<(TOuter Outer, TInner? Inner)> LeftJoin<TOuter, TInner, TKey>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, TKey> outerKeySelector, System.Func<TInner, TKey> innerKeySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
         public static System.Threading.Tasks.ValueTask<long> LongCountAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, bool> predicate, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Threading.Tasks.ValueTask<long> LongCountAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<bool>> predicate, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
         public static System.Threading.Tasks.ValueTask<long> LongCountAsync<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Threading.CancellationToken cancellationToken = default(System.Threading.CancellationToken)) { throw null; }
@@ -114,6 +118,8 @@ public static partial class AsyncEnumerable
         public static System.Collections.Generic.IAsyncEnumerable<TSource> Reverse<TSource>(this System.Collections.Generic.IAsyncEnumerable<TSource> source) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> RightJoin<TOuter, TInner, TKey, TResult>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> outerKeySelector, System.Func<TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> innerKeySelector, System.Func<TOuter?, TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TResult>> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> RightJoin<TOuter, TInner, TKey, TResult>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, TKey> outerKeySelector, System.Func<TInner, TKey> innerKeySelector, System.Func<TOuter?, TInner, TResult> resultSelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
+        public static System.Collections.Generic.IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> outerKeySelector, System.Func<TInner, System.Threading.CancellationToken, System.Threading.Tasks.ValueTask<TKey>> innerKeySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
+        public static System.Collections.Generic.IAsyncEnumerable<(TOuter? Outer, TInner Inner)> RightJoin<TOuter, TInner, TKey>(this System.Collections.Generic.IAsyncEnumerable<TOuter> outer, System.Collections.Generic.IAsyncEnumerable<TInner> inner, System.Func<TOuter, TKey> outerKeySelector, System.Func<TInner, TKey> innerKeySelector, System.Collections.Generic.IEqualityComparer<TKey>? comparer = null) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, System.Collections.Generic.IAsyncEnumerable<TResult>> selector) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, System.Collections.Generic.IEnumerable<TResult>> selector) { throw null; }
         public static System.Collections.Generic.IAsyncEnumerable<TResult> SelectMany<TSource, TResult>(this System.Collections.Generic.IAsyncEnumerable<TSource> source, System.Func<TSource, int, System.Collections.Generic.IAsyncEnumerable<TResult>> selector) { throw null; }

src/libraries/System.Linq.AsyncEnumerable/src/System/Linq/Join.cs

@@ -156,5 +156,140 @@ static async IAsyncEnumerable<TResult> Impl(
                 }
             }
         }
+
+        /// <summary>Correlates the elements of two sequences based on matching keys.</summary>
+        /// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
+        /// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
+        /// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
+        /// <param name="outer">The first sequence to join.</param>
+        /// <param name="inner">The sequence to join to the first sequence.</param>
+        /// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
+        /// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
+        /// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to use to hash and compare keys.</param>
+        /// <returns>
+        /// An <see cref="IAsyncEnumerable{T}"/> that has elements of type <c>(TOuter Outer, TInner Inner)</c>
+        /// that are obtained by performing an inner join on two sequences.
+        /// </returns>
+        /// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
+        public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
+            this IAsyncEnumerable<TOuter> outer,
+            IAsyncEnumerable<TInner> inner,
+            Func<TOuter, TKey> outerKeySelector,
+            Func<TInner, TKey> innerKeySelector,
+            IEqualityComparer<TKey>? comparer = null)
+        {
+            ArgumentNullException.ThrowIfNull(outer);
+            ArgumentNullException.ThrowIfNull(inner);
+            ArgumentNullException.ThrowIfNull(outerKeySelector);
+            ArgumentNullException.ThrowIfNull(innerKeySelector);
+
+            return
+                outer.IsKnownEmpty() || inner.IsKnownEmpty() ? Empty<(TOuter Outer, TInner Inner)>() :
+                Impl(outer, inner, outerKeySelector, innerKeySelector, comparer, default);
+
+            static async IAsyncEnumerable<(TOuter Outer, TInner Inner)> Impl(
+                IAsyncEnumerable<TOuter> outer, IAsyncEnumerable<TInner> inner,
+                Func<TOuter, TKey> outerKeySelector,
+                Func<TInner, TKey> innerKeySelector,
+                IEqualityComparer<TKey>? comparer,
+                [EnumeratorCancellation] CancellationToken cancellationToken)
+            {
+                await using IAsyncEnumerator<TOuter> e = outer.GetAsyncEnumerator(cancellationToken);
+
+                if (await e.MoveNextAsync())
+                {
+                    AsyncLookup<TKey, TInner> lookup = await AsyncLookup<TKey, TInner>.CreateForJoinAsync(inner, innerKeySelector, comparer, cancellationToken);
+                    if (lookup.Count != 0)
+                    {
+                        do
+                        {
+                            TOuter item = e.Current;
+                            Grouping<TKey, TInner>? g = lookup.GetGrouping(outerKeySelector(item), create: false);
+                            if (g is not null)
+                            {
+                                int count = g._count;
+                                TInner[] elements = g._elements;
+                                for (int i = 0; i != count; ++i)
+                                {
+                                    yield return (item, elements[i]);
+                                }
+                            }
+                        }
+                        while (await e.MoveNextAsync());
+                    }
+                }
+            }
+        }
+
+        /// <summary>Correlates the elements of two sequences based on matching keys.</summary>
+        /// <typeparam name="TOuter">The type of the elements of the first sequence.</typeparam>
+        /// <typeparam name="TInner">The type of the elements of the second sequence.</typeparam>
+        /// <typeparam name="TKey">The type of the keys returned by the key selector functions.</typeparam>
+        /// <param name="outer">The first sequence to join.</param>
+        /// <param name="inner">The sequence to join to the first sequence.</param>
+        /// <param name="outerKeySelector">A function to extract the join key from each element of the first sequence.</param>
+        /// <param name="innerKeySelector">A function to extract the join key from each element of the second sequence.</param>
+        /// <param name="comparer">An <see cref="IEqualityComparer{T}"/> to use to hash and compare keys.</param>
+        /// <returns>
+        /// An <see cref="IAsyncEnumerable{T}"/> that has elements of type <c>(TOuter Outer, TInner Inner)</c>
+        /// that are obtained by performing an inner join on two sequences.
+        /// </returns>
+        /// <exception cref="ArgumentNullException"><paramref name="outer" /> is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="inner" /> is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="outerKeySelector" /> is <see langword="null" />.</exception>
+        /// <exception cref="ArgumentNullException"><paramref name="innerKeySelector" /> is <see langword="null" />.</exception>
+        public static IAsyncEnumerable<(TOuter Outer, TInner Inner)> Join<TOuter, TInner, TKey>(
+            this IAsyncEnumerable<TOuter> outer,
+            IAsyncEnumerable<TInner> inner,
+            Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
+            Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
+            IEqualityComparer<TKey>? comparer = null)
+        {
+            ArgumentNullException.ThrowIfNull(outer);
+            ArgumentNullException.ThrowIfNull(inner);
+            ArgumentNullException.ThrowIfNull(outerKeySelector);
+            ArgumentNullException.ThrowIfNull(innerKeySelector);
+
+            return
+                outer.IsKnownEmpty() || inner.IsKnownEmpty() ? Empty<(TOuter Outer, TInner Inner)>() :
+                Impl(outer, inner, outerKeySelector, innerKeySelector, comparer, default);
+
+            static async IAsyncEnumerable<(TOuter Outer, TInner Inner)> Impl(
+                IAsyncEnumerable<TOuter> outer,
+                IAsyncEnumerable<TInner> inner,
+                Func<TOuter, CancellationToken, ValueTask<TKey>> outerKeySelector,
+                Func<TInner, CancellationToken, ValueTask<TKey>> innerKeySelector,
+                IEqualityComparer<TKey>? comparer,
+                [EnumeratorCancellation] CancellationToken cancellationToken)
+            {
+                await using IAsyncEnumerator<TOuter> e = outer.GetAsyncEnumerator(cancellationToken);
+
+                if (await e.MoveNextAsync())
+                {
+                    AsyncLookup<TKey, TInner> lookup = await AsyncLookup<TKey, TInner>.CreateForJoinAsync(inner, innerKeySelector, comparer, cancellationToken);
+                    if (lookup.Count != 0)
+                    {
+                        do
+                        {
+                            TOuter item = e.Current;
+                            Grouping<TKey, TInner>? g = lookup.GetGrouping(await outerKeySelector(item, cancellationToken), create: false);
+                            if (g is not null)
+                            {
+                                int count = g._count;
+                                TInner[] elements = g._elements;
+                                for (int i = 0; i != count; ++i)
+                                {
+                                    yield return (item, elements[i]);
+                                }
+                            }
+                        }
+                        while (await e.MoveNextAsync());
+                    }
+                }
+            }
+        }
     }
 }