Bring JSON type out of experimental status (#36442)

* Remove experimental warning
* Remove conversion to nvarchar(max) within OPENJSON
* Add conversions to nvarchar(max) when comparing json
  (not natively supported)
* Use json type in complex JSON query tests when targeting newer
  versions of SQL Server
* Various test tweaks and cleanup

Closes #36024

Author: roji

src/EFCore.SqlServer/Diagnostics/Internal/SqlServerLoggingDefinitions.cs

@@ -194,12 +194,4 @@ public class SqlServerLoggingDefinitions : RelationalLoggingDefinitions
     ///     doing so can result in application failures when updating to a new Entity Framework Core release.
     /// </summary>
     public EventDefinitionBase? LogMissingViewDefinitionRights;
-
-    /// <summary>
-    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
-    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
-    ///     any release. You should only use it directly in your code with extreme caution and knowing that
-    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
-    /// </summary>
-    public EventDefinitionBase? LogJsonTypeExperimental;
 }

src/EFCore.SqlServer/Diagnostics/SqlServerEventId.cs

@@ -32,7 +32,7 @@ private enum Id
         ConflictingValueGenerationStrategiesWarning,
         DecimalTypeKeyWarning,
         SavepointsDisabledBecauseOfMARS,
-        JsonTypeExperimental,
+        JsonTypeExperimental, // No longer used
 
         // Scaffolding events
         ColumnFound = CoreEventId.ProviderDesignBaseId,
@@ -115,20 +115,6 @@ private static EventId MakeValidationId(Id id)
     /// </remarks>
     public static readonly EventId ByteIdentityColumnWarning = MakeValidationId(Id.ByteIdentityColumnWarning);
 
-    /// <summary>
-    ///     An entity type makes use of the SQL Server native 'json' type. Please note that support for this type in EF Core 9 is
-    ///     experimental and may change in future releases.
-    /// </summary>
-    /// <remarks>
-    ///     <para>
-    ///         This event is in the <see cref="DbLoggerCategory.Model.Validation" /> category.
-    ///     </para>
-    ///     <para>
-    ///         This event uses the <see cref="EntityTypeEventData" /> payload when used with a <see cref="DiagnosticSource" />.
-    ///     </para>
-    /// </remarks>
-    public static readonly EventId JsonTypeExperimental = MakeValidationId(Id.JsonTypeExperimental);
-
     /// <summary>
     ///     There are conflicting value generation methods for a property.
     /// </summary>

src/EFCore.SqlServer/Extensions/Internal/SqlServerLoggerExtensions.cs

@@ -124,33 +124,6 @@ private static string ByteIdentityColumnWarning(EventDefinitionBase definition,
             p.Property.DeclaringType.DisplayName());
     }
 
-    /// <summary>
-    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
-    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
-    ///     any release. You should only use it directly in your code with extreme caution and knowing that
-    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
-    /// </summary>
-    public static void JsonTypeExperimental(
-        this IDiagnosticsLogger<DbLoggerCategory.Model.Validation> diagnostics,
-        IEntityType entityType)
-    {
-        var definition = SqlServerResources.LogJsonTypeExperimental(diagnostics);
-
-        if (diagnostics.ShouldLog(definition))
-        {
-            definition.Log(diagnostics, entityType.DisplayName());
-        }
-
-        if (diagnostics.NeedsEventData(definition, out var diagnosticSourceEnabled, out var simpleLogEnabled))
-        {
-            var eventData = new EntityTypeEventData(
-                definition, (d, p)
-                    => ((EventDefinition<string>)d).GenerateMessage(((EntityTypeEventData)p).EntityType.DisplayName()), entityType);
-
-            diagnostics.DispatchEventData(definition, eventData, diagnosticSourceEnabled, simpleLogEnabled);
-        }
-    }
-
     /// <summary>
     ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
     ///     the same compatibility standards as public APIs. It may be changed or removed without notice in

src/EFCore.SqlServer/Infrastructure/Internal/SqlServerModelValidator.cs

@@ -48,27 +48,6 @@ public override void Validate(IModel model, IDiagnosticsLogger<DbLoggerCategory.
         ValidateVectorColumns(model, logger);
         ValidateByteIdentityMapping(model, logger);
         ValidateTemporalTables(model, logger);
-        ValidateUseOfJsonType(model, logger);
-    }
-
-    /// <summary>
-    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
-    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
-    ///     any release. You should only use it directly in your code with extreme caution and knowing that
-    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
-    /// </summary>
-    protected virtual void ValidateUseOfJsonType(
-        IModel model,
-        IDiagnosticsLogger<DbLoggerCategory.Model.Validation> logger)
-    {
-        foreach (var entityType in model.GetEntityTypes())
-        {
-            if (string.Equals(entityType.GetContainerColumnType(), "json", StringComparison.OrdinalIgnoreCase)
-                || entityType.GetProperties().Any(p => string.Equals(p.GetColumnType(), "json", StringComparison.OrdinalIgnoreCase)))
-            {
-                logger.JsonTypeExperimental(entityType);
-            }
-        }
     }
 
     /// <summary>

src/EFCore.SqlServer/Properties/SqlServerStrings.Designer.cs

@@ -264,10 +264,6 @@
     <value>Found unique constraint on table '{tableName}' with name '{uniqueConstraintName}'.</value>
     <comment>Debug SqlServerEventId.UniqueConstraintFound string string</comment>
   </data>
-  <data name="LogJsonTypeExperimental" xml:space="preserve">
-    <value>The entity type '{entityType}' makes use of the SQL Server native 'json' type. Please note that support for this type in EF Core 9 is experimental and may change in future releases.</value>
-    <comment>Warning SqlServerEventId.JsonTypeExperimental string</comment>
-  </data>
   <data name="LogMissingSchema" xml:space="preserve">
     <value>Unable to find a schema in the database matching the selected schema '{schema}'.</value>
     <comment>Warning SqlServerEventId.MissingSchemaWarning string?</comment>

src/EFCore.SqlServer/Properties/SqlServerStrings.resx

@@ -254,21 +254,28 @@ when _columnsToRewrite.TryGetValue((columnExpression.TableAlias, columnExpressio
                     jsonScalar.IsNullable);
             }
 
-            case SqlServerOpenJsonExpression openJsonExpression:
-                // Currently, OPENJSON does not accept a "json" type, so we must cast the value to a string.
-                // We do this for both the case where is a string type mapping for a top-level property with the store type
-                // of "json", and when there is an "element" type mapping to something in the document but is now being used
-                // with OPENJSON.
-                return openJsonExpression.JsonExpression.TypeMapping
-                    is SqlServerStringTypeMapping { StoreType: "json" }
-                    or SqlServerStructuralJsonTypeMapping { StoreType: "json" }
-                    ? openJsonExpression.Update(
-                        new SqlUnaryExpression(
-                            ExpressionType.Convert,
-                            (SqlExpression)Visit(openJsonExpression.JsonExpression),
-                            typeof(string),
-                            typeMappingSource.FindMapping(typeof(string))!))
-                    : base.Visit(expression);
+            // The SQL Server json type cannot be compared ("The JSON data type cannot be compared or sorted, except when using the
+            // IS NULL operator"). So we find comparisons that involve the json type, and apply a conversion to string (nvarchar(max))
+            // to both sides. We exempt this when one of the sides is a constant null (not required).
+            case SqlBinaryExpression
+            {
+                OperatorType: ExpressionType.Equal or ExpressionType.NotEqual,
+                Left: var left,
+                Right: var right
+            } comparison
+                when (left.TypeMapping?.StoreType is "json" || right.TypeMapping?.StoreType is "json")
+                    && left is not SqlConstantExpression { Value: null } && right is not SqlConstantExpression { Value: null }:
+            {
+                return comparison.Update(
+                    sqlExpressionFactory.Convert(
+                        left,
+                        typeof(string),
+                        typeMappingSource.FindMapping(typeof(string))),
+                    sqlExpressionFactory.Convert(
+                        right,
+                        typeof(string),
+                        typeMappingSource.FindMapping(typeof(string))));
+            }
 
             default:
                 return base.Visit(expression);

src/EFCore.SqlServer/Query/Internal/SqlServerJsonPostprocessor.cs

@@ -2,37 +2,56 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 #nullable disable
+
 using Microsoft.Data.SqlClient;
+using Xunit.Sdk;
 
 namespace Microsoft.EntityFrameworkCore.Query;
 
 [SqlServerCondition(SqlServerCondition.SupportsJsonType)]
 public class AdHocJsonQuerySqlServerJsonTypeTest(NonSharedFixture fixture) : AdHocJsonQuerySqlServerTestBase(fixture)
 {
-    public override async Task Missing_navigation_works_with_deduplication(bool async)
-    {
-        // TODO:SQLJSON Returns empty (invalid) JSON (See BadJson.cs)
-        if (async)
-        {
-            Assert.Equal(
-                "Unable to cast object of type 'System.DBNull' to type 'System.String'.",
-                (await Assert.ThrowsAsync<InvalidCastException>(() => base.Missing_navigation_works_with_deduplication(true))).Message);
-        }
-        else
-        {
-            Assert.Equal(
-                RelationalStrings.JsonEmptyString,
-                (await Assert.ThrowsAsync<InvalidOperationException>(() => base.Missing_navigation_works_with_deduplication(false)))
-                .Message);
-        }
-    }
-
-    public override async Task Contains_on_nested_collection_with_init_only_navigation()
-        // TODO:SQLJSON (See JsonTypeToFunction.cs)
-        => Assert.Equal(
-            "OpenJson support not yet supported for JSON native data type.",
-            (await Assert.ThrowsAsync<SqlException>(
-                () => base.Contains_on_nested_collection_with_init_only_navigation())).Message);
+    #region BadJsonProperties
+
+    // When using the SQL Server JSON data type, insertion of the bad data fails thanks to SQL Server validation,
+    // unlike with tests mapping to nvarchar(max) where the bad JSON data is inserted correctly and then read.
+
+    public override Task Bad_json_properties_duplicated_navigations(bool noTracking)
+        => Task.CompletedTask;
+
+    public override Task Bad_json_properties_duplicated_scalars(bool noTracking)
+        => Task.CompletedTask;
+
+    public override Task Bad_json_properties_empty_navigations(bool noTracking)
+        => Task.CompletedTask;
+
+    public override Task Bad_json_properties_empty_scalars(bool noTracking)
+        => Task.CompletedTask;
+
+    public override Task Bad_json_properties_null_navigations(bool noTracking)
+        => Task.CompletedTask;
+
+    public override Task Bad_json_properties_null_scalars(bool noTracking)
+        => Task.CompletedTask;
+
+    #endregion BadJsonProperties
+
+    // SQL Server 2025 (CTP 2.1) does not support casting JSON scalar strings to json
+    // (CAST('8' AS json) and CAST('null' AS json) fail with "JSON text is not properly formatted").
+    public override Task Project_entity_with_json_null_values()
+        => Assert.ThrowsAsync<SqlException>(base.Project_entity_with_json_null_values);
+
+    // SQL Server 2025 (CTP 2.1) does not support casting JSON scalar strings to json
+    // (CAST('8' AS json) and CAST('null' AS json) fail with "JSON text is not properly formatted").
+    // The base implementation expects a different exception.
+    public override Task Try_project_collection_but_JSON_is_entity()
+        => Assert.ThrowsAsync<ThrowsException>(base.Try_project_collection_but_JSON_is_entity);
+
+    // SQL Server 2025 (CTP 2.1) does not support casting JSON scalar strings to json
+    // (CAST('8' AS json) and CAST('null' AS json) fail with "JSON text is not properly formatted").
+    // The base implementation expects a different exception.
+    public override Task Try_project_reference_but_JSON_is_collection()
+        => Assert.ThrowsAsync<ThrowsException>(base.Try_project_reference_but_JSON_is_collection);
 
     protected override string StoreName
         => "AdHocJsonQueryJsonTypeTest";

test/EFCore.SqlServer.FunctionalTests/Query/AdHocJsonQuerySqlServerJsonTypeTest.cs

@@ -3,6 +3,4 @@
 
 namespace Microsoft.EntityFrameworkCore.Query;
 
-public class AdHocJsonQuerySqlServerTest(NonSharedFixture fixture) : AdHocJsonQuerySqlServerTestBase(fixture)
-{
-}
+public class AdHocJsonQuerySqlServerTest(NonSharedFixture fixture) : AdHocJsonQuerySqlServerTestBase(fixture);