[Python] Fix quotation of union string cases (#3819)

* Fix quotation of union string cases

* Fix fix single case

src/Fable.Cli/CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 * [JS/TS] Fixed TimeSpan.FromMilliseconds (#3815) (by @ncave)
+* [Python] Fixed quotation for union string cases (by @dbrattli)
 
 ## 4.17.0 - 2024-04-23
 

src/fable-library-py/fable_library/types.py

@@ -55,8 +55,7 @@ def __init__(self):
 
     @staticmethod
     @abstractmethod
-    def cases() -> list[str]:
-        ...
+    def cases() -> list[str]: ...
 
     @property
     def name(self) -> str:
@@ -66,14 +65,19 @@ def __str__(self) -> str:
         if not len(self.fields):
             return self.name
 
+        def to_string(value: Any) -> str:
+            if isinstance(value, str):
+                return f'"{value}"'
+            return str(value)
+
         fields = ""
         with_parens = True
         if len(self.fields) == 1:
-            field = str(self.fields[0])
+            field = to_string(self.fields[0])
             with_parens = field.find(" ") >= 0
             fields = field
         else:
-            fields = ", ".join(map(str, self.fields))
+            fields = ", ".join(map(to_string, self.fields))
 
         return self.name + (" (" if with_parens else " ") + fields + (")" if with_parens else "")
 
@@ -204,8 +208,7 @@ def __hash__(self) -> int:
         return record_get_hashcode(self)
 
 
-class Attribute:
-    ...
+class Attribute: ...
 
 
 def seq_to_string(self: Iterable[Any]) -> str:

tests/Python/TestUnionType.fs

@@ -205,3 +205,9 @@ let ``test Equality works in filter`` () =
     |> Array.filter (fun r -> r.Case = MyUnion3.Case1)
     |> Array.length
     |> equal 2
+
+type S = S of string
+[<Fact>]
+let ``test sprintf formats strings cases correctly`` () =
+    let s = sprintf "%A" (S "1")
+    s |> equal "S \"1\""