[Docs] [C#] Update docs with List<T> returns and IEnumerable<T> tests

crates/bindings-csharp/Codegen.Tests/fixtures/diag/Lib.cs

@@ -1,3 +1,4 @@
+using System.Collections.Generic;
 using System.ComponentModel;
 using SpacetimeDB;
 
@@ -554,20 +555,36 @@ public static List<Player> ViewDefWrongContext(ReducerContext ctx)
     }
 
     // TODO: Investigate why void return breaks the FFI generation
-    // // Invalid: Void return type is not Vec<T> or Option<T>
+    // // Invalid: Void return type is not List<T> or T?
     // [SpacetimeDB.View(Accessor = "view_def_no_return", Public = true)]
     // public static void ViewDefNoReturn(ViewContext ctx)
     // {
     //     return;
     // }
 
-    // Invalid: Wrong return type is not Vec<T> or Option<T>
+    // Invalid: Wrong return type is not List<T> or T?
     [SpacetimeDB.View(Accessor = "view_def_wrong_return", Public = true)]
     public static Player ViewDefWrongReturn(ViewContext ctx)
     {
         return new Player { Identity = new() };
     }
 
+    // Invalid: IEnumerable<T> return type (from Iter()) is not List<T> or T?
+    [SpacetimeDB.View(Accessor = "view_def_ienumerable_return_from_iter", Public = true)]
+    public static IEnumerable<Player> ViewDefIEnumerableReturnFromIter(ViewContext ctx)
+    {
+        return ctx.Db.Player.Iter();
+    }
+
+    // Invalid: IEnumerable<T> return type (from Filter()) is not List<T> or T?
+    [SpacetimeDB.View(Accessor = "view_def_ienumerable_return_from_filter", Public = true)]
+    public static IEnumerable<TestScheduleIssues> ViewDefIEnumerableReturnFromFilter(
+        ViewContext ctx
+    )
+    {
+        return ctx.Db.TestIndexIssues.TestUnexpectedColumns.Filter(0);
+    }
+
     // Invalid: Returns type that is not a SpacetimeType
     [SpacetimeDB.View(Accessor = "view_def_returns_not_a_spacetime_type", Public = true)]
     public static NotSpacetimeType? ViewDefReturnsNotASpacetimeType(AnonymousViewContext ctx)

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/ExtraCompilationErrors.verified.txt

@@ -114,6 +114,29 @@ SpacetimeDB.Internal.Module.RegisterClientVisibilityFilter(global::Module.MY_FOU
       ]
     }
   },
+  {/*
+    {
+        return ctx.Db.Player.Iter();
+                             ^^^^
+    }
+*/
+    Message: 'PlayerReadOnly' does not contain a definition for 'Iter' and no accessible extension method 'Iter' accepting a first argument of type 'PlayerReadOnly' could be found (are you missing a using directive or an assembly reference?),
+    Severity: Error,
+    Descriptor: {
+      Id: CS1061,
+      Title: ,
+      HelpLink: https://msdn.microsoft.com/query/roslyn.query?appId=roslyn&k=k(CS1061),
+      MessageFormat: '{0}' does not contain a definition for '{1}' and no accessible extension method '{1}' accepting a first argument of type '{0}' could be found (are you missing a using directive or an assembly reference?),
+      Category: Compiler,
+      DefaultSeverity: Error,
+      IsEnabledByDefault: true,
+      CustomTags: [
+        Compiler,
+        Telemetry,
+        NotConfigurable
+      ]
+    }
+  },
   {/*
     {
         ctx.Db.Player.Iter();
@@ -275,6 +298,29 @@ SpacetimeDB.Internal.Module.RegisterClientVisibilityFilter(global::Module.MY_THI
       ]
     }
   },
+  {/*
+    {
+        return ctx.Db.TestIndexIssues.TestUnexpectedColumns.Filter(0);
+               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    }
+*/
+    Message: Cannot implicitly convert type 'System.Collections.Generic.IEnumerable<TestIndexIssues>' to 'System.Collections.Generic.IEnumerable<TestScheduleIssues>'. An explicit conversion exists (are you missing a cast?),
+    Severity: Error,
+    Descriptor: {
+      Id: CS0266,
+      Title: ,
+      HelpLink: https://msdn.microsoft.com/query/roslyn.query?appId=roslyn&k=k(CS0266),
+      MessageFormat: Cannot implicitly convert type '{0}' to '{1}'. An explicit conversion exists (are you missing a cast?),
+      Category: Compiler,
+      DefaultSeverity: Error,
+      IsEnabledByDefault: true,
+      CustomTags: [
+        Compiler,
+        Telemetry,
+        NotConfigurable
+      ]
+    }
+  },
   {/*
 
             var returnValue = Module.ViewDefNoContext((SpacetimeDB.ViewContext)ctx);

crates/bindings-csharp/Codegen.Tests/fixtures/diag/snapshots/Module.verified.txt

@@ -330,7 +330,7 @@ public partial struct TestScheduleIssues
       }
     },
     {/*
-    // Invalid: Wrong return type is not Vec<T> or Option<T>
+    // Invalid: Wrong return type is not List<T> or T?
     [SpacetimeDB.View(Accessor = "view_def_wrong_return", Public = true)]
     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     public static Player ViewDefWrongReturn(ViewContext ctx)
@@ -355,6 +355,94 @@ public partial struct TestScheduleIssues
       }
     },
     {/*
+    [SpacetimeDB.View(Accessor = "view_def_ienumerable_return_from_iter", Public = true)]
+    public static IEnumerable<Player> ViewDefIEnumerableReturnFromIter(ViewContext ctx)
+                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    {
+*/
+      Message: BSATN implementation for System.Collections.Generic.IEnumerable<Player> is not found: Unsupported system type System.Collections.Generic.IEnumerable<T>,
+      Severity: Error,
+      Descriptor: {
+        Id: BSATN0001,
+        Title: Unsupported type,
+        MessageFormat: BSATN implementation for {0} is not found: {1},
+        Category: SpacetimeDB.BSATN,
+        DefaultSeverity: Error,
+        IsEnabledByDefault: true
+      }
+    },
+    {/*
+    // Invalid: IEnumerable<T> return type (from Iter()) is not List<T> or T?
+    [SpacetimeDB.View(Accessor = "view_def_ienumerable_return_from_iter", Public = true)]
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    public static IEnumerable<Player> ViewDefIEnumerableReturnFromIter(ViewContext ctx)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    {
+^^^^^
+        return ctx.Db.Player.Iter();
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    }
+^^^^^
+
+*/
+      Message: View 'ViewDefIEnumerableReturnFromIter' must return Vec<T> or Option<T>.,
+      Severity: Error,
+      Descriptor: {
+        Id: STDB0024,
+        Title: Views must return Vec<T> or Option<T>,
+        MessageFormat: View '{0}' must return Vec<T> or Option<T>.,
+        Category: SpacetimeDB,
+        DefaultSeverity: Error,
+        IsEnabledByDefault: true
+      }
+    },
+    {/*
+    [SpacetimeDB.View(Accessor = "view_def_ienumerable_return_from_filter", Public = true)]
+    public static IEnumerable<TestScheduleIssues> ViewDefIEnumerableReturnFromFilter(
+                                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+        ViewContext ctx
+*/
+      Message: BSATN implementation for System.Collections.Generic.IEnumerable<TestScheduleIssues> is not found: Unsupported system type System.Collections.Generic.IEnumerable<T>,
+      Severity: Error,
+      Descriptor: {
+        Id: BSATN0001,
+        Title: Unsupported type,
+        MessageFormat: BSATN implementation for {0} is not found: {1},
+        Category: SpacetimeDB.BSATN,
+        DefaultSeverity: Error,
+        IsEnabledByDefault: true
+      }
+    },
+    {/*
+    // Invalid: IEnumerable<T> return type (from Filter()) is not List<T> or T?
+    [SpacetimeDB.View(Accessor = "view_def_ienumerable_return_from_filter", Public = true)]
+    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    public static IEnumerable<TestScheduleIssues> ViewDefIEnumerableReturnFromFilter(
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+        ViewContext ctx
+^^^^^^^^^^^^^^^^^^^^^^^
+    )
+^^^^^
+    {
+^^^^^
+        return ctx.Db.TestIndexIssues.TestUnexpectedColumns.Filter(0);
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+    }
+^^^^^
+
+*/
+      Message: View 'ViewDefIEnumerableReturnFromFilter' must return Vec<T> or Option<T>.,
+      Severity: Error,
+      Descriptor: {
+        Id: STDB0024,
+        Title: Views must return Vec<T> or Option<T>,
+        MessageFormat: View '{0}' must return Vec<T> or Option<T>.,
+        Category: SpacetimeDB,
+        DefaultSeverity: Error,
+        IsEnabledByDefault: true
+      }
+    },
+    {/*
     [SpacetimeDB.Reducer]
     public static int TestReducerReturnType(ReducerContext ctx) => 0;
                   ^^^