Fix LIKE escape type mapping with value converters

Keep LIKE and ILIKE escape expressions independent from match and pattern type mapping so property converters cannot rewrite provider-generated escape values.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Copilot-Session: e5b861c2-ea5b-411c-8efe-3d925d29c52e

Author: roji

src/EFCore.PG/Query/NpgsqlSqlExpressionFactory.cs

@@ -394,6 +394,7 @@ public virtual PgFunctionExpression AggregateFunction(
             sqlExpression = sqlExpression switch
             {
                 SqlBinaryExpression e => ApplyTypeMappingOnSqlBinary(e, typeMapping),
+                LikeExpression e => ApplyTypeMappingOnLike(e),
 
                 // PostgreSQL-specific expression types
                 PgAnyExpression e => ApplyTypeMappingOnAny(e),
@@ -710,20 +711,30 @@ private SqlExpression ApplyTypeMappingOnArraySlice(
             array.TypeMapping);
     }
 
+    // The base implementation is private, so duplicate it here to keep the escape character's type mapping independent.
+    private SqlExpression ApplyTypeMappingOnLike(LikeExpression likeExpression)
+    {
+        var inferredTypeMapping = ExpressionExtensions.InferTypeMapping(likeExpression.Match, likeExpression.Pattern)
+            ?? _typeMappingSource.FindMapping(likeExpression.Match.Type, Dependencies.Model);
+
+        return new LikeExpression(
+            ApplyTypeMapping(likeExpression.Match, inferredTypeMapping),
+            ApplyTypeMapping(likeExpression.Pattern, inferredTypeMapping),
+            // The escape character must not inherit the match or pattern's value converter (#3888).
+            ApplyDefaultTypeMapping(likeExpression.EscapeChar),
+            _boolTypeMapping);
+    }
+
     private SqlExpression ApplyTypeMappingOnILike(PgILikeExpression ilikeExpression)
     {
-        var inferredTypeMapping = (ilikeExpression.EscapeChar is null
-                ? ExpressionExtensions.InferTypeMapping(
-                    ilikeExpression.Match, ilikeExpression.Pattern)
-                : ExpressionExtensions.InferTypeMapping(
-                    ilikeExpression.Match, ilikeExpression.Pattern,
-                    ilikeExpression.EscapeChar))
+        var inferredTypeMapping = ExpressionExtensions.InferTypeMapping(ilikeExpression.Match, ilikeExpression.Pattern)
             ?? _typeMappingSource.FindMapping(ilikeExpression.Match.Type, Dependencies.Model);
 
         return new PgILikeExpression(
             ApplyTypeMapping(ilikeExpression.Match, inferredTypeMapping),
             ApplyTypeMapping(ilikeExpression.Pattern, inferredTypeMapping),
-            ApplyTypeMapping(ilikeExpression.EscapeChar, inferredTypeMapping),
+            // The escape character must not inherit the match or pattern's value converter (#3888).
+            ApplyDefaultTypeMapping(ilikeExpression.EscapeChar),
             _boolTypeMapping);
     }
 

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

@@ -80,4 +80,57 @@ public static DateTime Modify(DateTime date)
                 => throw new NotSupportedException();
         }
     }
+
+    [ConditionalFact]
+    public virtual async Task Like_with_implicit_escape_does_not_apply_value_converter()
+    {
+        var contextFactory = await InitializeNonSharedTest<Context3888>(
+            seed: async context =>
+            {
+                context.Entities.Add(new Context3888.Entity { Value = "ABC" });
+                await context.SaveChangesAsync();
+            });
+
+        await using var context = contextFactory.CreateDbContext();
+
+        var pattern = "%ABC%";
+
+        Assert.Equal(1, await context.Entities.CountAsync(e => EF.Functions.Like(e.Value!, pattern)));
+        Assert.Equal(1, await context.Entities.CountAsync(e => EF.Functions.ILike(e.Value!, pattern)));
+
+        AssertSql(
+            """
+@pattern='%ABC%'
+
+SELECT count(*)::int
+FROM "Entities" AS e
+WHERE e."Value" LIKE @pattern ESCAPE ''
+""",
+            //
+            """
+@pattern='%ABC%'
+
+SELECT count(*)::int
+FROM "Entities" AS e
+WHERE e."Value" ILIKE @pattern ESCAPE ''
+""");
+    }
+
+    protected class Context3888(DbContextOptions options) : DbContext(options)
+    {
+        public DbSet<Entity> Entities { get; set; } = null!;
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+            => modelBuilder.Entity<Entity>()
+                .Property(e => e.Value)
+                .HasConversion(
+                    value => string.IsNullOrWhiteSpace(value) ? null : value,
+                    value => value ?? string.Empty);
+
+        public class Entity
+        {
+            public int Id { get; set; }
+            public string? Value { get; set; }
+        }
+    }
 }