Fix CSV schema parsing: column names with parentheses no longer corrupt type annotation

The nameAndTypeRegex used RegexOptions.RightToLeft, which caused incorrect
splits when a column name contained parentheses. For example, the schema
"Na(  )me (int)" was parsed as name="Na", type="  )me (int)" instead of
the correct name="Na(  )me", type="int".

Without RightToLeft, the greedy .+ quantifier on the name group naturally
backtracks and matches the *last* "(type)" group at the end of the string,
which is the correct behaviour.

Fixes #946.

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

Author: 2 people

src/FSharp.Data.Csv.Core/CsvInference.fs

@@ -36,7 +36,10 @@ let private nameToTypeForCsv =
     |> dict
 
 let private nameAndTypeRegex =
-    lazy Regex(@"^(?<name>.+)\((?<type>.+)\)$", RegexOptions.Compiled ||| RegexOptions.RightToLeft)
+    // Note: do NOT use RightToLeft here — it causes incorrect splits when the column name
+    // itself contains parentheses (e.g. "Na(  )me (type)" would give name="Na", type="  )me (type").
+    // Without RightToLeft, greedy backtracking correctly matches the *last* "(type)" group.
+    lazy Regex(@"^(?<name>.+)\((?<type>.+)\)$", RegexOptions.Compiled)
 
 let private overrideByNameRegex =
     lazy

tests/FSharp.Data.DesignTime.Tests/InferenceTests.fs

@@ -359,6 +359,20 @@ let ``Inference schema override by parameter``() =
 
   actual |> should equal expected
 
+[<Test>]
+let ``Column name with parentheses is parsed correctly in schema`` () =
+  // Regression test for https://github.com/fsprojects/FSharp.Data/issues/946
+  // A column name like "Na(  )me" must not be split at the first '(' when the
+  // schema type annotation "(int)" appears at the end.
+  let source = CsvFile.Parse("Na(  )me,other\n1,2")
+  let actual =
+    inferType source Int32.MaxValue [||] culture "Na(  )me (int),other (string)" false false
+    ||> CsvInference.getFields false
+    |> List.map (fun field -> field.Name, field.Value.RuntimeType)
+
+  let expected = [ "Na(  )me", typeof<int>; "other", typeof<string> ]
+  actual |> should equal expected
+
 [<Test>]
 let ``Doesn't infer 12-002 as a date``() =
   // a previous version inferred a IntOrStringOrDateTime