Translate List.Count inside json (#2376)

Fixes #2374

(cherry picked from commit e946af8)

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlArrayTranslator.cs

@@ -143,8 +143,7 @@ public NpgsqlArrayTranslator(
         // The array/list CLR type may be mapped to a non-array database type (e.g. byte[] to bytea, or just
         // value converters) - we don't want to translate for those cases.
         static bool IsMappedToNonArray(SqlExpression arrayOrList)
-            => arrayOrList.TypeMapping is RelationalTypeMapping typeMapping &&
-                typeMapping is not (NpgsqlArrayTypeMapping or NpgsqlJsonTypeMapping);
+            => arrayOrList.TypeMapping is RelationalTypeMapping and not (NpgsqlArrayTypeMapping or NpgsqlJsonTypeMapping);
 
         SqlExpression? TranslateCommon(SqlExpression arrayOrList, IReadOnlyList<SqlExpression> arguments)
         {

src/EFCore.PG/Query/ExpressionTranslators/Internal/NpgsqlJsonPocoTranslator.cs

@@ -33,26 +33,37 @@ public NpgsqlJsonPocoTranslator(
         _stringTypeMapping = typeMappingSource.FindMapping(typeof(string), model)!;
     }
 
-    public virtual SqlExpression? Translate(SqlExpression? instance,
+    public virtual SqlExpression? Translate(
+        SqlExpression? instance,
         MemberInfo member,
         Type returnType,
         IDiagnosticsLogger<DbLoggerCategory.Query> logger)
-        => instance?.TypeMapping is NpgsqlJsonTypeMapping || instance is PostgresJsonTraversalExpression
-            ? TranslateMemberAccess(
-                instance,
-                _sqlExpressionFactory.Constant(
-                    member.GetCustomAttribute<JsonPropertyNameAttribute>()?.Name ?? member.Name),
-                returnType)
-            : null;
+    {
+        if (instance?.TypeMapping is not NpgsqlJsonTypeMapping && instance is not PostgresJsonTraversalExpression)
+        {
+            return null;
+        }
+
+        if (member.Name == nameof(List<object>.Count)
+            && member.DeclaringType?.IsGenericType == true
+            && member.DeclaringType.GetGenericTypeDefinition() == typeof(List<>))
+        {
+            return TranslateArrayLength(instance);
+        }
+
+        return TranslateMemberAccess(
+            instance,
+            _sqlExpressionFactory.Constant(member.GetCustomAttribute<JsonPropertyNameAttribute>()?.Name ?? member.Name),
+            returnType);
+    }
 
     public virtual SqlExpression? TranslateMemberAccess(
         SqlExpression instance, SqlExpression member, Type returnType)
     {
         // The first time we see a JSON traversal it's on a column - create a JsonTraversalExpression.
         // Traversals on top of that get appended into the same expression.
 
-        if (instance is ColumnExpression columnExpression &&
-            columnExpression.TypeMapping is NpgsqlJsonTypeMapping)
+        if (instance is ColumnExpression { TypeMapping: NpgsqlJsonTypeMapping } columnExpression)
         {
             return ConvertFromText(
                 _sqlExpressionFactory.JsonTraversal(
@@ -76,8 +87,7 @@ public NpgsqlJsonPocoTranslator(
 
     public virtual SqlExpression? TranslateArrayLength(SqlExpression expression)
     {
-        if (expression is ColumnExpression columnExpression &&
-            columnExpression.TypeMapping is NpgsqlJsonTypeMapping mapping)
+        if (expression is ColumnExpression { TypeMapping: NpgsqlJsonTypeMapping mapping })
         {
             return _sqlExpressionFactory.Function(
                 mapping.IsJsonb ? "jsonb_array_length" : "json_array_length",

test/EFCore.PG.FunctionalTests/Query/JsonDomQueryTest.cs

@@ -105,7 +105,7 @@ public void Parameter_element()
 WHERE j.""Id"" = @__p_0
 LIMIT 1",
             //
-            @"@__expected_0='{""ID"": ""00000000-0000-0000-0000-000000000000"", ""Age"": 25, ""Name"": ""Joe"", ""IsVip"": false, ""Orders"": [{""Price"": 99.5, ""ShippingAddress"": ""Some address 1""}, {""Price"": 23, ""ShippingAddress"": ""Some address 2""}], ""Statistics"": {""Nested"": {""IntArray"": [3, 4], ""SomeProperty"": 10, ""SomeNullableInt"": 20, ""SomeNullableGuid"": ""d5f2685d-e5c4-47e5-97aa-d0266154eb2d""}, ""Visits"": 4, ""Purchases"": 3}, ""VariousTypes"": {""Bool"": ""false"", ""Int16"": 8, ""Int32"": 8, ""Int64"": 8, ""String"": ""foo"", ""Decimal"": 10, ""DateTime"": ""2020-01-01T10:30:45"", ""DateTimeOffset"": ""2020-01-01T10:30:45+02:00""}}' (DbType = Object)
+            @"@__expected_0='{""ID"": ""00000000-0000-0000-0000-000000000000"", ""Age"": 25, ""Name"": ""Joe"", ""IsVip"": false, ""Orders"": [{""Price"": 99.5, ""ShippingAddress"": ""Some address 1""}, {""Price"": 23, ""ShippingAddress"": ""Some address 2""}], ""Statistics"": {""Nested"": {""IntList"": [3, 4], ""IntArray"": [3, 4], ""SomeProperty"": 10, ""SomeNullableInt"": 20, ""SomeNullableGuid"": ""d5f2685d-e5c4-47e5-97aa-d0266154eb2d""}, ""Visits"": 4, ""Purchases"": 3}, ""VariousTypes"": {""Bool"": ""false"", ""Int16"": 8, ""Int32"": 8, ""Int64"": 8, ""String"": ""foo"", ""Decimal"": 10, ""DateTime"": ""2020-01-01T10:30:45"", ""DateTimeOffset"": ""2020-01-01T10:30:45+02:00""}}' (DbType = Object)
 
 SELECT j.""Id"", j.""CustomerDocument"", j.""CustomerElement""
 FROM ""JsonbEntities"" AS j
@@ -522,7 +522,8 @@ static JsonDocument CreateCustomer1() => JsonDocument.Parse(@"
                             ""SomeProperty"": 10,
                             ""SomeNullableInt"": 20,
                             ""SomeNullableGuid"": ""d5f2685d-e5c4-47e5-97aa-d0266154eb2d"",
-                            ""IntArray"": [3, 4]
+                            ""IntArray"": [3, 4],
+                            ""IntList"": [3, 4]
                         }
                     },
                     ""Orders"":
@@ -564,7 +565,8 @@ static JsonDocument CreateCustomer2() => JsonDocument.Parse(@"
                             ""SomeProperty"": 20,
                             ""SomeNullableInt"": null,
                             ""SomeNullableGuid"": null,
-                            ""IntArray"": [5, 6]
+                            ""IntArray"": [5, 6, 7],
+                            ""IntArray"": [5, 6, 7]
                         }
                     },
                     ""Orders"":

test/EFCore.PG.FunctionalTests/Query/JsonPocoQueryTest.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Text.Json;
@@ -309,27 +310,59 @@ WHERE CAST(j.""Customer""#>>ARRAY['Statistics','Nested','IntArray',@__i_0]::TEXT
     public void Array_Length()
     {
         using var ctx = CreateContext();
-        var x = ctx.JsonbEntities.Single(e => e.Customer.Orders.Length == 2);
+        var x = ctx.JsonbEntities.Single(e => e.Customer.Statistics.Nested.IntArray.Length == 2);
 
         Assert.Equal("Joe", x.Customer.Name);
         AssertSql(
             @"SELECT j.""Id"", j.""Customer"", j.""ToplevelArray""
 FROM ""JsonbEntities"" AS j
-WHERE jsonb_array_length(j.""Customer""->'Orders') = 2
+WHERE jsonb_array_length(j.""Customer""#>'{Statistics,Nested,IntArray}') = 2
 LIMIT 2");
     }
 
     [Fact]
     public void Array_Length_json()
     {
         using var ctx = CreateContext();
-        var x = ctx.JsonEntities.Single(e => e.Customer.Orders.Length == 2);
+        var x = ctx.JsonEntities.Single(e => e.Customer.Statistics.Nested.IntArray.Length == 2);
 
         Assert.Equal("Joe", x.Customer.Name);
         AssertSql(
             @"SELECT j.""Id"", j.""Customer"", j.""ToplevelArray""
 FROM ""JsonEntities"" AS j
-WHERE json_array_length(j.""Customer""->'Orders') = 2
+WHERE json_array_length(j.""Customer""#>'{Statistics,Nested,IntArray}') = 2
+LIMIT 2");
+    }
+
+    [Fact]
+    public void List_Count()
+    {
+        using var ctx = CreateContext();
+
+        var x = ctx.JsonbEntities.Single(e => e.Customer.Statistics.Nested.IntList.Count == 2);
+
+        Assert.Equal("Joe", x.Customer.Name);
+
+        AssertSql(
+            @"SELECT j.""Id"", j.""Customer"", j.""ToplevelArray""
+FROM ""JsonbEntities"" AS j
+WHERE jsonb_array_length(j.""Customer""#>'{Statistics,Nested,IntList}') = 2
+LIMIT 2");
+    }
+
+    [Fact]
+    public void List_Count_json()
+    {
+        using var ctx = CreateContext();
+
+        var x = ctx.JsonEntities.Single(e => e.Customer.Statistics.Nested.IntList.Count == 2);
+
+        Assert.Equal("Joe", x.Customer.Name);
+
+        AssertSql(
+            @"SELECT j.""Id"", j.""Customer"", j.""ToplevelArray""
+FROM ""JsonEntities"" AS j
+WHERE json_array_length(j.""Customer""#>'{Statistics,Nested,IntList}') = 2
 LIMIT 2");
     }
 
@@ -585,7 +618,8 @@ public static void Seed(JsonPocoQueryContext context)
                         SomeProperty = 10,
                         SomeNullableInt = 20,
                         SomeNullableGuid = Guid.Parse("d5f2685d-e5c4-47e5-97aa-d0266154eb2d"),
-                        IntArray = new[] { 3, 4 }
+                        IntArray = new[] { 3, 4 },
+                        IntList = new() { 3, 4 }
                     }
                 },
                 Orders = new[]
@@ -629,7 +663,8 @@ public static void Seed(JsonPocoQueryContext context)
                         SomeProperty = 20,
                         SomeNullableInt = null,
                         SomeNullableGuid = null,
-                        IntArray = new[] { 5, 6 }
+                        IntArray = new[] { 5, 6, 7 },
+                        IntList = new() { 5, 6, 7 }
                     }
                 },
                 Orders = new[]
@@ -709,6 +744,7 @@ public class NestedStatistics
         public int SomeProperty { get; set; }
         public int? SomeNullableInt { get; set; }
         public int[] IntArray { get; set; }
+        public List<int> IntList { get; set; }
         public Guid? SomeNullableGuid { get; set; }
     }