Draft: Improve typing support for _TupleParser

funcparserlib/parser.py

@@ -66,6 +66,7 @@
 
 import logging
 import warnings
+import sys
 from typing import (
     Any,
     Callable,
@@ -82,13 +83,20 @@
 
 from funcparserlib.lexer import Token
 
+if sys.version_info >= (3, 11):
+    from typing import TypeVarTuple, Unpack
+else:
+    from typing_extensions import TypeVarTuple, Unpack
+
+
 log = logging.getLogger("funcparserlib")
 
 debug = False
 
 _A = TypeVar("_A")
 _B = TypeVar("_B")
 _C = TypeVar("_C")
+_Ts = TypeVarTuple("_Ts")
 
 
 class Parser(Generic[_A, _B]):
@@ -273,13 +281,13 @@ def __add__(  # type: ignore[misc]
         pass
 
     @overload
-    def __add__(self, other: "Parser[_A, _C]") -> "_TupleParser[_A, Tuple[_B, _C]]":
+    def __add__(self, other: "Parser[_A, _C]") -> "_TupleParser[_A, _B, _C]":
         pass
 
     def __add__(
         self,
         other: Union["_IgnoredParser[_A]", "Parser[_A, _C]"],
-    ) -> Union["Parser[_A, _B]", "_TupleParser[_A, Tuple[_B, _C]]"]:
+    ) -> Union["Parser[_A, _B]", "_TupleParser[_A, _B, _C]"]:
         """Sequential combination of parsers. It runs this parser, then the other
         parser.
 
@@ -551,18 +559,22 @@ class _Tuple(tuple):
     pass
 
 
-class _TupleParser(Parser[_A, _B], Generic[_A, _B]):
-    @overload  # type: ignore[override]
-    def __add__(self, other: "_IgnoredParser[_A]") -> "_TupleParser[_A, _B]":
+class _TupleParser(Parser[_A, Tuple[Unpack[_Ts]]], Generic[_A, Unpack[_Ts]]):
+    @overload  # type: ignore[override, overload-overlap]
+    def __add__(self, other: "_IgnoredParser[_A]") -> "_TupleParser[_A, Unpack[_Ts]]":
         pass
 
     @overload
-    def __add__(self, other: Parser[_A, Any]) -> Parser[_A, Any]:
+    def __add__(self, other: Parser[_A, _B]) -> "_TupleParser[_A, Unpack[_Ts], _B]":
         pass
 
     def __add__(
-        self, other: Union["_IgnoredParser[_A]", Parser[_A, Any]]
-    ) -> Union["_TupleParser[_A, _B]", Parser[_A, Any]]:
+        self,
+        other: Union[
+            "_IgnoredParser[_A]",
+            Parser[_A, _B],
+        ],
+    ) -> Union["_TupleParser[_A, Unpack[_Ts]]", "_TupleParser[_A, Unpack[_Ts], _B]"]:
         return super().__add__(other)
 
 

pyproject.toml

@@ -21,6 +21,7 @@ classifiers = [
 
 [tool.poetry.dependencies]
 python = "^3.8"
+typing-extensions = {version = ">=4.1.0", python = "<3.11"}
 
 [tool.poetry.dev-dependencies]
 pre-commit = {version = "^3.5.0"}

tests/test_parsing.py

@@ -12,6 +12,7 @@
     Parser,
     maybe,
     _Ignored,  # noqa
+    _TupleParser,  # noqa
     tok,
     finished,
     forward_decl,
@@ -103,7 +104,7 @@ def test_ok_ignored_ok(self) -> None:
     def test_ok_ok_ok(self) -> None:
         x = a("x")
         y = a("y")
-        expr: Parser[str, Tuple[str, str]] = x + y + x
+        expr: _TupleParser[str, str, str, str] = x + y + x
         self.assertEqual(expr.parse("xyx"), ("x", "y", "x"))
 
     def test_ok_ok_ignored(self) -> None: