[Python] regex cleanup (#3627)

* Python regex cleanup

* Update changelog

src/Fable.Cli/CHANGELOG.md

@@ -14,6 +14,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 * Fix #3615: Fix remove from dictionary with tuple as key
 * Fix #3598: Using obj () now generated an empty dict instead of None
 * Fix #3597: Do not translate .toString methods to str
+* Fix #3610: Cleanup Python regex handling
 
 ## 4.6.0 - 2023-11-27
 

src/Fable.Transforms/Python/Replacements.fs

@@ -5529,6 +5529,9 @@ let regex
         | Some(ExprType(DeclaredTypeFullName Types.regexGroup)) -> true
         | _ -> false
 
+    let createRegex r t args =
+        Helper.LibCall(com, "RegExp", "create", t, args, ?loc = r)
+
     match i.CompiledName with
     // TODO: Use RegexConst if no options have been passed?
     | ".ctor" ->
@@ -5611,6 +5614,36 @@ let regex
     | "get_Count" ->
         Helper.GlobalCall("len", t, [ thisArg.Value ], [ t ], ?loc = r) |> Some
     | "GetEnumerator" -> getEnumerator com r t thisArg.Value |> Some
+    | "IsMatch"
+    | "Match"
+    | "Matches" as meth ->
+        match thisArg, args with
+        | Some thisArg, args ->
+            if args.Length > 2 then
+                $"Regex.{meth} doesn't support more than 2 arguments"
+                |> addError com ctx.InlinePath r
+
+            thisArg :: args |> Some
+        | None, input :: pattern :: args ->
+            let reg = createRegex None Any (pattern :: args)
+
+            [
+                reg
+                input
+            ]
+            |> Some
+        | _ -> None
+        |> Option.map (fun args ->
+            Helper.LibCall(
+                com,
+                "RegExp",
+                Naming.lowerFirst meth,
+                t,
+                args,
+                i.SignatureArgTypes,
+                ?loc = r
+            )
+        )
     | meth ->
         let meth = Naming.removeGetSetPrefix meth |> Naming.lowerFirst
 

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

@@ -56,28 +56,15 @@ def unescape(string: str) -> str:
     return re.sub(r"\\(.)", r"\1", string)
 
 
-def match(reg: Pattern[str] | str, input: str, start_at: int = 0) -> Match[str] | None:
-    if isinstance(reg, str):
-        flags = _options_to_flags(start_at)
-        return re.search(input, reg, flags)
+def match(reg: Pattern[str], input: str, start_at: int = 0) -> Match[str] | None:
     return reg.search(input, pos=start_at)
 
 
 def matches(reg: Pattern[str], input: str, start_at: int = 0) -> list[Match[str]]:
-    if isinstance(reg, str):
-        flags = _options_to_flags(start_at)
-        input = input.replace("?<", "?P<")
-        return list(re.finditer(input, reg, flags=flags))
-
     return list(reg.finditer(input, pos=start_at))
 
 
-def is_match(reg: Pattern[str] | str, input: str, start_at: int = 0) -> bool:
-    if isinstance(reg, str):
-        # Note: input is the pattern here
-        flags = _options_to_flags(start_at)
-        return re.search(input, reg, flags=flags) is not None
-
+def is_match(reg: Pattern[str], input: str, start_at: int = 0) -> bool:
     return reg.search(input, pos=start_at) is not None