Block EF7 JSON usage

Closes npgsql#2452

Author: roji

src/EFCore.PG/Infrastructure/Internal/NpgsqlModelValidator.cs

@@ -193,6 +193,20 @@ static void ValidateSproc(IStoredProcedure sproc, IDiagnosticsLogger<DbLoggerCat
         }
     }
 
+    /// <inheritdoc />
+    protected override void ValidateJsonEntities(
+        IModel model,
+        IDiagnosticsLogger<DbLoggerCategory.Model.Validation> logger)
+    {
+        foreach (var entityType in model.GetEntityTypes())
+        {
+            if (entityType.IsMappedToJson())
+            {
+                throw new InvalidOperationException(NpgsqlStrings.Ef7JsonMappingNotSupported);
+            }
+        }
+    }
+
     /// <inheritdoc />
     protected override void ValidateCompatible(
         IProperty property,

src/EFCore.PG/Metadata/Internal/NpgsqlAnnotationProvider.cs

@@ -1,3 +1,5 @@
+using Microsoft.EntityFrameworkCore.Metadata.Internal;
+
 namespace Npgsql.EntityFrameworkCore.PostgreSQL.Metadata.Internal;
 
 /// <summary>
@@ -127,11 +129,11 @@ public override IEnumerable<IAnnotation> For(IColumn column, bool designTime)
                     .ToArray());
         }
 
-        // Model validation ensures that these facets are the same on all mapped properties
-        var property = column.PropertyMappings.First().Property;
-
-        if (property.GetCompressionMethod() is { } compressionMethod)
+        // JSON columns have no property mappings so all annotations that rely on property mappings should be skipped for them
+        if (column is not JsonColumn
+            && column.PropertyMappings.FirstOrDefault()?.Property.GetCompressionMethod() is { } compressionMethod)
         {
+            // Model validation ensures that these facets are the same on all mapped properties
             yield return new Annotation(NpgsqlAnnotationNames.CompressionMethod, compressionMethod);
         }
     }

src/EFCore.PG/Properties/NpgsqlStrings.Designer.cs

@@ -132,6 +132,9 @@
   <data name="DuplicateIndexIncludedMismatch" xml:space="preserve">
     <value>The indexes {index1} on '{entityType1}' and {index2} on '{entityType2}' are both mapped to '{table}.{indexName}', but have different included columns: {includedColumns1} and {includedColumns2}.</value>
   </data>
+  <data name="Ef7JsonMappingNotSupported" xml:space="preserve">
+    <value>The EF Core 7.0 JSON support isn't currently supported by the Npgsql provider. To map to JSON, see https://www.npgsql.org/efcore/mapping/json.html.</value>
+  </data>
   <data name="FreeTextFunctionOnClient" xml:space="preserve">
     <value>The 'FreeText' method is not supported because the query has switched to client-evaluation. Inspect the log to determine which query expressions are triggering client-evaluation.</value>
   </data>

src/EFCore.PG/Properties/NpgsqlStrings.resx

@@ -64,6 +64,7 @@ public override void PropagateResults(RelationalDataReader relationalReader)
 
                 case IColumn:
                 case IStoreStoredProcedureParameter:
+                case null when columnModification.JsonPath is not null:
                     continue;
 
                 default: