Add some missing translations for DateTimeOffset

Fixes npgsql#2119

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

@@ -32,6 +32,14 @@ public NpgsqlDateTimeMemberTranslator(
         IDiagnosticsLogger<DbLoggerCategory.Query> logger)
     {
         var type = member.DeclaringType;
+
+        if (type == typeof(DateTimeOffset)
+            && instance is not null
+            && TranslateDateTimeOffset(instance, member, returnType) is { } translated)
+        {
+            return translated;
+        }
+
         if (type != typeof(DateTime)
             && type != typeof(DateTimeOffset)
             && type != typeof(DateOnly)
@@ -147,4 +155,22 @@ private SqlExpression GetDatePartExpression(
 
         return _sqlExpressionFactory.Convert(result, typeof(int));
     }
+
+    public virtual SqlExpression? TranslateDateTimeOffset(
+        SqlExpression instance,
+        MemberInfo member,
+        Type returnType)
+        => member.Name switch
+        {
+            // We only support UTC DateTimeOffset, so DateTimeOffset.DateTime is just a matter of converting to timestamp without time zone
+            nameof(DateTimeOffset.DateTime)      => _sqlExpressionFactory.AtUtc(instance),
+
+            // We only support UTC DateTimeOffset, so DateTimeOffset.UtcDateTime does nothing (type change on CLR change, no change on the
+            // PG side.
+            nameof(DateTimeOffset.UtcDateTime)   => instance,
+
+            // Convert to timestamp without time zone, applying a time zone conversion based on the TimeZone connection parameter.
+            nameof(DateTimeOffset.LocalDateTime) => _sqlExpressionFactory.Convert(instance, typeof(DateTime), _timestampMapping),
+            _ => null
+        };
 }

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

@@ -332,6 +332,66 @@ await AssertQuery(
 
     #endregion Now
 
+    #region DateTimeOffset
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public async Task DateTimeOffset_DateTime(bool async)
+    {
+        // We only support UTC DateTimeOffset, so DateTimeOffset.DateTime is just a matter of converting to timestamp without time zone
+        await AssertQuery(
+            async,
+            ss => ss.Set<Entity>().Where(
+                e => e.TimestampDateTimeOffset.DateTime == new DateTime(1998, 4, 12, 13, 26, 38, DateTimeKind.Unspecified)),
+            entryCount: 1);
+
+        AssertSql(
+            @"SELECT e.""Id"", e.""TimestampDateTime"", e.""TimestampDateTimeArray"", e.""TimestampDateTimeOffset"", e.""TimestampDateTimeOffsetArray"", e.""TimestampDateTimeRange"", e.""TimestamptzDateTime"", e.""TimestamptzDateTimeArray"", e.""TimestamptzDateTimeRange""
+FROM ""Entities"" AS e
+WHERE e.""TimestampDateTimeOffset"" AT TIME ZONE 'UTC' = TIMESTAMP '1998-04-12 13:26:38'");
+    }
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public async Task DateTimeOffset_UtcDateTime(bool async)
+    {
+        // We only support UTC DateTimeOffset, so DateTimeOffset.UtcDateTime does nothing (type change on CLR change, no change on the
+        // PG side.
+        await AssertQuery(
+            async,
+            ss => ss.Set<Entity>().Where(
+                e => e.TimestampDateTimeOffset.UtcDateTime == new DateTime(1998, 4, 12, 13, 26, 38, DateTimeKind.Utc)),
+            entryCount: 1);
+
+        AssertSql(
+            @"SELECT e.""Id"", e.""TimestampDateTime"", e.""TimestampDateTimeArray"", e.""TimestampDateTimeOffset"", e.""TimestampDateTimeOffsetArray"", e.""TimestampDateTimeRange"", e.""TimestamptzDateTime"", e.""TimestamptzDateTimeArray"", e.""TimestamptzDateTimeRange""
+FROM ""Entities"" AS e
+WHERE e.""TimestampDateTimeOffset"" = TIMESTAMPTZ '1998-04-12 13:26:38Z'");
+    }
+
+    [ConditionalFact]
+    public async Task DateTimeOffset_LocalDateTime()
+    {
+        // Note that we're in the Europe/Berlin timezone (see NpgsqlTestStore below)
+
+        // We can't use AssertQuery since the local (expected) evaluation is dependent on the machine's timezone, which is out of
+        // our control.
+        await using var ctx = CreateContext();
+
+        var count = await ctx.Set<Entity>()
+            .Where(e => e.TimestampDateTimeOffset.LocalDateTime == new DateTime(1998, 4, 12, 15, 26, 38, DateTimeKind.Local))
+            .CountAsync();
+
+        Assert.Equal(1, count);
+
+        AssertSql(
+            @"SELECT COUNT(*)::INT
+FROM ""Entities"" AS e
+WHERE e.""TimestampDateTimeOffset""::timestamp = TIMESTAMP '1998-04-12 15:26:38'");
+    }
+
+    #endregion DateTimeOffset
+
     #region DateTime constructors
 
     [ConditionalTheory]
@@ -725,4 +785,4 @@ public static IReadOnlyList<Entity> CreateEntities()
     }
 
     #endregion
-}
+}