Throw for empty strings in primitive collection columns (#32924)

Fixes #32896

Author: ajcvickers

src/EFCore/Properties/CoreStrings.Designer.cs

@@ -486,6 +486,9 @@
   <data name="EmptyComplexType" xml:space="preserve">
     <value>Complex type '{complexType}' has no properties defines. Configure at least one property or don't include this type in the model.</value>
   </data>
+  <data name="EmptyJsonString" xml:space="preserve">
+    <value>The empty string is not valid JSON.</value>
+  </data>
   <data name="EntityEqualityOnCompositeKeyEntitySubqueryNotSupported" xml:space="preserve">
     <value>Cannot translate '{comparisonOperator}' on a subquery expression of entity type '{entityType}' because it has a composite primary key. See https://go.microsoft.com/fwlink/?linkid=2141942 for information on how to rewrite your query.</value>
   </data>

src/EFCore/Properties/CoreStrings.resx

@@ -63,6 +63,11 @@ internal JsonValueReaderWriter()
     /// <returns>The read value.</returns>
     public object FromJsonString(string json, object? existingObject = null)
     {
+        if (string.IsNullOrWhiteSpace(json))
+        {
+            throw new InvalidOperationException(CoreStrings.EmptyJsonString);
+        }
+
         var readerManager = new Utf8JsonReaderManager(new JsonReaderData(Encoding.UTF8.GetBytes(json)), null);
         return FromJson(ref readerManager, existingObject);
     }

src/EFCore/Storage/Json/JsonValueReaderWriter.cs

@@ -1317,6 +1317,48 @@ FROM json_each(@__strings_0) AS "s"
 """);
     }
 
+    [ConditionalTheory]
+    [InlineData(false)]
+    [InlineData(true)] // Issue #32896
+    public async Task Empty_string_used_for_primitive_collection_throws(bool async)
+    {
+        await using var connection = new SqliteConnection("DataSource=:memory:");
+        await connection.OpenAsync();
+
+        await using var context = new SimpleContext(connection);
+        await context.Database.EnsureDeletedAsync();
+        await context.Database.EnsureCreatedAsync();
+
+        await context.Database.ExecuteSqlRawAsync("INSERT INTO SimpleEntities (List) VALUES ('');");
+
+        var set = context.SimpleEntities;
+
+        var message = await Assert.ThrowsAsync<InvalidOperationException>(
+            async () =>
+            {
+                if (async)
+                {
+                    await set.FirstAsync();
+                }
+                else
+                {
+                    set.First();
+                }
+            });
+
+        Assert.Equal(CoreStrings.EmptyJsonString, message.Message);
+    }
+
+    public class SimpleContext(SqliteConnection connection) : DbContext
+    {
+        public DbSet<SimpleEntity> SimpleEntities => Set<SimpleEntity>();
+
+        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
+            => optionsBuilder.UseSqlite(connection);
+    }
+
+    public record SimpleEntity(int Id, IEnumerable<string> List);
+
     [ConditionalFact]
     public virtual void Check_all_tests_overridden()
         => TestHelpers.AssertAllMethodsOverridden(GetType());