From 195cca898651060eda0d7f7fc499b9c3e38ca05a Mon Sep 17 00:00:00 2001
From: Marc Gravell <marc.gravell@gmail.com>
Date: Thu, 20 Aug 2026 05:28:28 +0100
Subject: [PATCH] CommandUtils.As: accept a DateOnly source (Npgsql 10 'date'
 columns)

Npgsql 10 changed reader.GetValue() for a 'date' column to return DateOnly
rather than DateTime; DateOnly does not implement IConvertible, so the
As<DateTime[?]> fallback through Convert.ToDateTime threw InvalidCastException.
Bisected empirically: the DateOnlyTimeOnly Postgres tests pass on Npgsql 9.0.2
and fail on 10.0.2, which arrived with #174 - unseen because the Postgres
integration tests need local Docker.

As<DateTime[?]> now converts via ToDateTime(TimeOnly.MinValue), and
As<TimeOnly[?]> answers default for a date - the same answer a zero-time
DateTime gives, which is the contract the integration test documents. New
docker-free unit tests cover the matrix directly, so this coverage no longer
depends on a live container.

Fixes #202
---
 src/Dapper.AOT/Internal/CommandUtils.cs       | 26 ++++++++++++
 .../CommandUtilsDateOnlyTests.cs              | 40 +++++++++++++++++++
 2 files changed, 66 insertions(+)
 create mode 100644 test/Dapper.AOT.Test/CommandUtilsDateOnlyTests.cs

diff --git a/src/Dapper.AOT/Internal/CommandUtils.cs b/src/Dapper.AOT/Internal/CommandUtils.cs
index 997274b7..19d5e2fa 100644
--- a/src/Dapper.AOT/Internal/CommandUtils.cs
+++ b/src/Dapper.AOT/Internal/CommandUtils.cs
@@ -157,11 +157,26 @@ internal static T As<T>(object? value)
             }
             else if (typeof(T) == typeof(DateTime))
             {
+#if NET6_0_OR_GREATER
+                // Npgsql 10 hands back DateOnly for "date" columns; not IConvertible
+                if (value is DateOnly dateOnlySource)
+                {
+                    DateTime fromDateOnly = dateOnlySource.ToDateTime(TimeOnly.MinValue);
+                    return Unsafe.As<DateTime, T>(ref fromDateOnly);
+                }
+#endif
                 DateTime t = Convert.ToDateTime(value, CultureInfo.InvariantCulture);
                 return Unsafe.As<DateTime, T>(ref t);
             }
             else if (typeof(T) == typeof(DateTime?))
             {
+#if NET6_0_OR_GREATER
+                if (value is DateOnly dateOnlySource)
+                {
+                    DateTime? fromDateOnly = dateOnlySource.ToDateTime(TimeOnly.MinValue);
+                    return Unsafe.As<DateTime?, T>(ref fromDateOnly);
+                }
+#endif
                 DateTime? t = Convert.ToDateTime(value, CultureInfo.InvariantCulture);
                 return Unsafe.As<DateTime?, T>(ref t);
             }
@@ -187,6 +202,12 @@ internal static T As<T>(object? value)
                     var fromSpan = TimeOnly.FromTimeSpan(timeSpan);
                     return Unsafe.As<TimeOnly, T>(ref fromSpan);
                 }
+                if (value is DateOnly)
+                {
+                    // a date has no time component; same answer a zero-time DateTime gives
+                    TimeOnly zero = default;
+                    return Unsafe.As<TimeOnly, T>(ref zero);
+                }
 
                 DateTime t = Convert.ToDateTime(value, CultureInfo.InvariantCulture);
                 var timeOnly = TimeOnly.FromDateTime(t);
@@ -199,6 +220,11 @@ internal static T As<T>(object? value)
                     var fromSpan = TimeOnly.FromTimeSpan(timeSpan);
                     return Unsafe.As<TimeOnly, T>(ref fromSpan);
                 }
+                if (value is DateOnly)
+                {
+                    TimeOnly? zero = default(TimeOnly);
+                    return Unsafe.As<TimeOnly?, T>(ref zero);
+                }
 
                 DateTime? t = Convert.ToDateTime(value, CultureInfo.InvariantCulture);
                 TimeOnly? timeOnly = t is null ? null : TimeOnly.FromDateTime(t.Value);
diff --git a/test/Dapper.AOT.Test/CommandUtilsDateOnlyTests.cs b/test/Dapper.AOT.Test/CommandUtilsDateOnlyTests.cs
new file mode 100644
index 00000000..f3cce1c9
--- /dev/null
+++ b/test/Dapper.AOT.Test/CommandUtilsDateOnlyTests.cs
@@ -0,0 +1,40 @@
+#if NET6_0_OR_GREATER
+using System;
+using Dapper.Internal;
+using Xunit;
+
+namespace Dapper.AOT.Test
+{
+    // Npgsql 10 hands back DateOnly (not DateTime) for "date" columns; these are the
+    // docker-free half of DateOnlyTimeOnlyPostgreSqlTests, so the coverage does not
+    // depend on a live container (see #202)
+    public class CommandUtilsDateOnlyTests
+    {
+        private static readonly object BoxedDateOnly = new DateOnly(2021, 1, 2);
+
+        [Fact]
+        public void As_DateOnlyToDateTime()
+            => Assert.Equal(new DateTime(2021, 1, 2), CommandUtils.As<DateTime>(BoxedDateOnly));
+
+        [Fact]
+        public void As_DateOnlyToNullableDateTime()
+            => Assert.Equal(new DateTime(2021, 1, 2), CommandUtils.As<DateTime?>(BoxedDateOnly));
+
+        [Fact] // a date has no time component; same answer a zero-time DateTime gives
+        public void As_DateOnlyToTimeOnly()
+            => Assert.Equal(default, CommandUtils.As<TimeOnly>(BoxedDateOnly));
+
+        [Fact]
+        public void As_DateOnlyToNullableTimeOnly()
+            => Assert.Equal(default(TimeOnly), CommandUtils.As<TimeOnly?>(BoxedDateOnly));
+
+        [Fact] // pass-through, unchanged
+        public void As_DateOnlyToDateOnly()
+            => Assert.Equal(new DateOnly(2021, 1, 2), CommandUtils.As<DateOnly>(BoxedDateOnly));
+
+        [Fact] // the pre-Npgsql-10 shape, unchanged
+        public void As_DateTimeToDateOnly()
+            => Assert.Equal(new DateOnly(2021, 1, 2), CommandUtils.As<DateOnly>((object)new DateTime(2021, 1, 2)));
+    }
+}
+#endif