From 9b8a4598cd98ba9810ed05ed4b697b0625820d44 Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Mon, 24 Oct 2022 14:48:06 +0200
Subject: [PATCH] Show that the NRE can also occur in synchronous versions of
 taskSeq

---
 .../TaskSeq.StateTransitionBug.Tests.CE.fs    | 147 +++++++++++++++++-
 1 file changed, 145 insertions(+), 2 deletions(-)

diff --git a/src/FSharpy.TaskSeq.Test/TaskSeq.StateTransitionBug.Tests.CE.fs b/src/FSharpy.TaskSeq.Test/TaskSeq.StateTransitionBug.Tests.CE.fs
index 43c0bbec..06e4e190 100644
--- a/src/FSharpy.TaskSeq.Test/TaskSeq.StateTransitionBug.Tests.CE.fs
+++ b/src/FSharpy.TaskSeq.Test/TaskSeq.StateTransitionBug.Tests.CE.fs
@@ -315,7 +315,7 @@ let ``CE taskSeq, call GetAsyncEnumerator twice -- random mixed iteration`` () =
 }
 
 [<Fact>]
-let ``CE taskSeq with two items, call map multiple times over its own result`` () = task {
+let ``CE taskSeq, call map multiple times over its own result`` () = task {
     let tskSeq = taskSeq {
         yield 1
         yield 2
@@ -333,7 +333,150 @@ let ``CE taskSeq with two items, call map multiple times over its own result`` (
 }
 
 [<Fact>]
-let ``CE taskSeq with two items, call mapAsync multiple times over its own result`` () = task {
+let ``CE taskSeq, call map multiple times over its own result - alternative #1`` () = task {
+    let tskSeq1 = taskSeq {
+        yield 1
+        yield 2
+    }
+
+    // [ 2; 3]
+    let tskSeq2 = taskSeq {
+        for i in tskSeq1 do
+            yield i + 1
+    }
+
+    // [ 3; 4]
+    let tskSeq3 = taskSeq {
+        for i in tskSeq2 do
+            yield i + 1
+    }
+
+    let result3 = TaskSeq.toArray tskSeq3
+
+    result3 |> should equal [| 3; 4 |]
+}
+
+[<Fact>]
+let ``CE taskSeq, call map multiple times over its own result - alternative #2`` () = task {
+    let tskSeq1 = taskSeq {
+        yield 1
+        yield 2
+    }
+
+    let result1 = TaskSeq.toArray tskSeq1
+    result1 |> should equal [| 1; 2 |]
+
+    // [ 2; 3]
+    let tskSeq2 = taskSeq {
+        for i in tskSeq1 do
+            yield i + 1
+    }
+
+    let result2 = TaskSeq.toArray tskSeq2
+    result2 |> should equal [| 2; 3 |]
+
+    // [ 3; 4]
+    let tskSeq3 = taskSeq {
+        for i in tskSeq2 do
+            yield i + 1
+    }
+
+    let result3 = TaskSeq.toArray tskSeq3
+    result3 |> should equal [| 3; 4 |]
+}
+
+[<Fact>]
+let ``CE taskSeq, call map multiple times over its own result - alternative #3`` () = task {
+    let tskSeq1 = taskSeq {
+        yield 1
+        yield 2
+    }
+
+    let result1 = TaskSeq.toArray tskSeq1
+    result1 |> should equal [| 1; 2 |]
+
+    // [ 2; 3]
+    let tskSeq2 = taskSeq {
+        yield! taskSeq {
+            for i in tskSeq1 do
+                yield i + 1
+        }
+    }
+
+    let result2 = TaskSeq.toArray tskSeq2
+    result2 |> should equal [| 2; 3 |]
+
+    // [ 3; 4]
+    let tskSeq3 = taskSeq {
+        yield! taskSeq {
+            for i in tskSeq2 do
+                yield i + 1
+        }
+    }
+
+    let result3 = TaskSeq.toArray tskSeq3
+    result3 |> should equal [| 3; 4 |]
+}
+
+[<Fact>]
+let ``CE taskSeq, call map multiple times over its own result - alternative #4`` () = task {
+    let sequence = seq {
+        yield 1
+        yield 2
+    }
+
+    // [ 2; 3]
+    let tskSeq2 = taskSeq {
+        for i in sequence do
+            yield i + 1
+    }
+
+    let result2 = TaskSeq.toArray tskSeq2
+    result2 |> should equal [| 2; 3 |]
+
+    // [ 3; 4]
+    let tskSeq3 = taskSeq {
+        for i in tskSeq2 do
+            yield i + 1
+    }
+
+    let result3 = TaskSeq.toArray tskSeq3
+    result3 |> should equal [| 3; 4 |]
+}
+
+[<Fact>]
+let ``CE taskSeq, call map multiple times over its own result - alternative #5`` () = task {
+    let sequence = seq {
+        yield 1
+        yield 2
+    }
+
+    // [ 2; 3]
+    let tskSeq2 = taskSeq {
+        yield! taskSeq {
+            for i in sequence do
+                yield i + 1
+        }
+    }
+
+    let result2 = TaskSeq.toArray tskSeq2
+    result2 |> should equal [| 2; 3 |]
+
+    // [ 3; 4]
+    let tskSeq3 = taskSeq {
+        yield! taskSeq {
+            for i in tskSeq2 do
+                yield i + 1
+        }
+    }
+
+    let result3 = TaskSeq.toArray tskSeq3
+    result3 |> should equal [| 3; 4 |]
+}
+
+
+[<Fact>]
+let ``CE taskSeq, call mapAsync multiple times over its own result`` () = task {
     let tskSeq = taskSeq {
         yield 1
         yield 2