fix: replace ToLower/ToUpper with culture-invariant equivalents for SQL identifiers

In Turkish locale (tr-TR), String.ToLower() converts 'I' to dotless 'ı' (U+0131)
instead of 'i', corrupting SQL identifiers (e.g. INFORMATION_SCHEMA →
ınformation_schema). Replace all .ToLower()/.ToUpper() calls that operate on SQL
identifiers, schema names, column names, type names, and keywords with
.ToLowerInvariant()/.ToUpperInvariant(). Adds unit tests that set
CultureInfo.CurrentCulture = tr-TR to verify correct normalization.

Upstream fix for JasperFx/wolverine#2472 (companion PR to JasperFx/wolverine#2480).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: jeremydmiller

src/Weasel.Core/Migrator.cs

@@ -78,13 +78,13 @@ public async Task ReadTemplatesAsync(string directory, CancellationToken ct = de
     {
         foreach (var file in FileSystem.FindFiles(directory, FileSet.Shallow("*.function")))
         {
-            var name = Path.GetFileNameWithoutExtension(file).ToLower();
+            var name = Path.GetFileNameWithoutExtension(file).ToLowerInvariant();
             Templates[name].FunctionCreation = await File.ReadAllTextAsync(file, ct).ConfigureAwait(false);
         }
 
         foreach (var file in FileSystem.FindFiles(directory, FileSet.Shallow("*.table")))
         {
-            var name = Path.GetFileNameWithoutExtension(file).ToLower();
+            var name = Path.GetFileNameWithoutExtension(file).ToLowerInvariant();
 
             Templates[name].TableCreation = await File.ReadAllTextAsync(file, ct).ConfigureAwait(false);
         }

src/Weasel.Postgresql.Tests/Tables/TableColumnTests.cs

@@ -1,3 +1,4 @@
+using System.Globalization;
 using NetTopologySuite.Geometries;
 using Shouldly;
 using Weasel.Postgresql.Tables;
@@ -143,4 +144,23 @@ public void to_function_update_should_quote_reserved_keywords(string keyword)
 
         column.ToFunctionUpdate().ShouldBe($"\"{keyword}\" = p_{keyword}");
     }
+
+    [Fact]
+    public void column_name_normalization_is_culture_invariant()
+    {
+        // In Turkish locale, "I".ToLower() produces dotless 'ı' (U+0131) instead of 'i',
+        // which would corrupt SQL identifiers like "INFORMATION_SCHEMA" → "ınformation_schema".
+        var originalCulture = CultureInfo.CurrentCulture;
+        try
+        {
+            CultureInfo.CurrentCulture = new CultureInfo("tr-TR");
+            var column = new TableColumn("INFORMATION_SCHEMA", "VARCHAR");
+            column.Name.ShouldBe("information_schema");
+            column.Type.ShouldBe("varchar");
+        }
+        finally
+        {
+            CultureInfo.CurrentCulture = originalCulture;
+        }
+    }
 }

src/Weasel.Postgresql.Tests/Tables/detecting_table_deltas.cs

@@ -67,13 +67,13 @@ public async Task using_reserved_keywords_for_columns()
     [MemberData(nameof(PostgresReservedKeywords))]
     public async Task verify_all_postgres_reserved_keywords_work_as_column_names(string keyword)
     {
-        var tableName = $"deltas.keyword_{keyword.ToLower()}";
+        var tableName = $"deltas.keyword_{keyword.ToLowerInvariant()}";
         var table = new Table(tableName);
         table.AddColumn<int>("id").AsPrimaryKey();
 
         await CreateSchemaObjectInDatabase(table);
 
-        table.AddColumn<string>(keyword.ToLower());
+        table.AddColumn<string>(keyword.ToLowerInvariant());
 
         await AssertNoDeltasAfterPatching(table);
     }

src/Weasel.Postgresql/Extension.cs

@@ -11,7 +11,7 @@ public class Extension: ISchemaObject
 {
     public Extension(string extensionName)
     {
-        ExtensionName = extensionName.Trim().ToLower();
+        ExtensionName = extensionName.Trim().ToLowerInvariant();
     }
 
     public string ExtensionName { get; }

src/Weasel.Postgresql/PostgresqlProvider.cs

@@ -98,7 +98,7 @@ protected override Type[] determineClrTypesForParameterType(NpgsqlDbType dbType)
 
     public string ConvertSynonyms(string type)
     {
-        switch (type.ToLower())
+        switch (type.ToLowerInvariant())
         {
             case "character varying":
             case "varchar":

src/Weasel.Postgresql/Tables/IndexDefinition.cs

@@ -390,7 +390,7 @@ public static IndexDefinition Parse(string definition)
         while (tokens.Any())
         {
             var current = tokens.Dequeue();
-            switch (current.ToUpper())
+            switch (current.ToUpperInvariant())
             {
                 case "CREATE":
                 case "CONCURRENTLY":

src/Weasel.Postgresql/Tables/TableColumn.cs

@@ -19,8 +19,8 @@ public TableColumn(string name, string type)
             throw new ArgumentOutOfRangeException(nameof(type));
         }
 
-        Name = name.ToLower().Trim().Replace(' ', '_');
-        Type = type.ToLower();
+        Name = name.ToLowerInvariant().Trim().Replace(' ', '_');
+        Type = type.ToLowerInvariant();
     }
 
 

src/Weasel.SqlServer.Tests/Tables/TableColumnTests.cs

@@ -1,3 +1,4 @@
+using System.Globalization;
 using Shouldly;
 using Weasel.SqlServer.Tables;
 using Xunit;
@@ -134,4 +135,23 @@ public void change_column_type_sql()
         table.ColumnFor(columnName)!.AlterColumnTypeSql(table, actualColumn)
             .ShouldBe($"alter table dbo.people alter column [{columnName}] varchar(200) NOT NULL;");
     }
+
+    [Fact]
+    public void column_name_normalization_is_culture_invariant()
+    {
+        // In Turkish locale, "I".ToLower() produces dotless 'ı' (U+0131) instead of 'i',
+        // which would corrupt SQL identifiers like "INFORMATION_SCHEMA" → "ınformation_schema".
+        var originalCulture = CultureInfo.CurrentCulture;
+        try
+        {
+            CultureInfo.CurrentCulture = new CultureInfo("tr-TR");
+            var column = new TableColumn("INFORMATION_SCHEMA", "VARCHAR");
+            column.Name.ShouldBe("information_schema");
+            column.Type.ShouldBe("varchar");
+        }
+        finally
+        {
+            CultureInfo.CurrentCulture = originalCulture;
+        }
+    }
 }

src/Weasel.SqlServer/SqlServerProvider.cs

@@ -87,7 +87,7 @@ public override string AddApplicationNameToConnectionString(string connectionStr
 
     public string ConvertSynonyms(string type)
     {
-        switch (type.ToLower())
+        switch (type.ToLowerInvariant())
         {
             case "text":
             case "varchar":
@@ -189,7 +189,7 @@ public override void SetParameterType(SqlParameter parameter, SqlDbType dbType)
 
     public static CascadeAction ReadAction(string description)
     {
-        switch (description.ToUpper().Trim())
+        switch (description.ToUpperInvariant().Trim())
         {
             case "CASCADE":
                 return CascadeAction.Cascade;

src/Weasel.SqlServer/Tables/Table.cs

@@ -128,7 +128,7 @@ public void WriteCreateStatement(Migrator migrator, TextWriter writer)
         if (migrator.TableCreation == CreationStyle.DropThenCreate)
         {
             // drop all FK constraints
-            var sqlVariableName = $"@sql_{Guid.NewGuid().ToString().ToLower().Replace("-", "_")}";
+            var sqlVariableName = $"@sql_{Guid.NewGuid().ToString().ToLowerInvariant().Replace("-", "_")}";
             writer.WriteLine("DECLARE {0} NVARCHAR(MAX) = '';", sqlVariableName);
             writer.WriteLine("SELECT {0} = {1} + 'ALTER TABLE ' + QUOTENAME(OBJECT_SCHEMA_NAME(fk.parent_object_id)) + '.' + QUOTENAME(OBJECT_NAME(fk.parent_object_id)) + ' DROP CONSTRAINT ' + QUOTENAME(fk.name) + ';'",
                 sqlVariableName, sqlVariableName);