Make it work on 3.9 again

turns out I have some systems where I care about that :)

pyproject.toml

@@ -20,13 +20,14 @@ name="chap"
 authors = [{name = "Jeff Epler", email = "jepler@gmail.com"}]
 description = "Interact with the OpenAI ChatGPT API (and other text generators)"
 dynamic = ["readme","version","dependencies"]
-requires-python = ">=3.10"
+requires-python = ">=3.9"
 keywords = ["llm", "tui", "chatgpt"]
 classifiers = [
     "Development Status :: 3 - Alpha",
     "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.9",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",
     "Programming Language :: Python :: 3.12",

src/chap/commands/ask.py

@@ -4,7 +4,7 @@
 
 import asyncio
 import sys
-from typing import Iterable, Protocol
+from typing import Iterable, Optional, Protocol
 
 import click
 import rich
@@ -40,7 +40,7 @@ class DumbPrinter:
 
 
 class WrappingPrinter:
-    def __init__(self, width: int | None = None) -> None:
+    def __init__(self, width: Optional[int] = None) -> None:
         self._width = width or rich.get_console().width
         self._column = 0
         self._line = ""

src/chap/commands/tui.py

@@ -5,7 +5,7 @@
 import asyncio
 import subprocess
 import sys
-from typing import Any, cast
+from typing import Any, Optional, cast
 
 from markdown_it import MarkdownIt
 from textual import work
@@ -63,7 +63,7 @@ class Tui(App[None]):
     ]
 
     def __init__(
-        self, api: Backend | None = None, session: Session | None = None
+        self, api: Optional[Backend] = None, session: Optional[Session] = None
     ) -> None:
         super().__init__()
         self.api = api or get_api("lorem")

src/chap/core.py

@@ -11,8 +11,7 @@ import pathlib
 import pkgutil
 import subprocess
 from dataclasses import MISSING, dataclass, fields
-from types import UnionType
+from typing import Any, AsyncGenerator, Callable, Optional, Union, cast
-from typing import Any, AsyncGenerator, Callable, cast
 
 import click
 import platformdirs
@@ -22,6 +21,9 @@ from typing_extensions import Protocol
 from . import backends, commands  # pylint: disable=no-name-in-module
 from .session import Message, Session, System, session_from_file
 
+# 3.9 compatible version of `from types import UnionType`
+UnionType = type(Union[int, list])
+
 conversations_path = platformdirs.user_state_path("chap") / "conversations"
 conversations_path.mkdir(parents=True, exist_ok=True)
 
@@ -54,14 +56,14 @@ class AutoAskMixin:  # pylint: disable=too-few-public-methods
         return "".join(tokens)
 
 
-def last_session_path() -> pathlib.Path | None:
+def last_session_path() -> Optional[pathlib.Path]:
     result = max(
         conversations_path.glob("*.json"), key=lambda p: p.stat().st_mtime, default=None
     )
     return result
 
 
-def new_session_path(opt_path: pathlib.Path | None = None) -> pathlib.Path:
+def new_session_path(opt_path: Optional[pathlib.Path] = None) -> pathlib.Path:
     return opt_path or conversations_path / (
         datetime.datetime.now().isoformat().replace(":", "_") + ".json"
     )
@@ -95,7 +97,7 @@ def get_api(name: str = "openai_chatgpt") -> Backend:
 
 
 def do_session_continue(
-    ctx: click.Context, param: click.Parameter, value: pathlib.Path | None
+    ctx: click.Context, param: click.Parameter, value: Optional[pathlib.Path]
 ) -> None:
     if value is None:
         return
@@ -293,18 +295,18 @@ def version_callback(  # pylint: disable=unused-argument
 
 @dataclass
 class Obj:
-    api: Backend | None = None
+    api: Optional[Backend] = None
-    system_message: str | None = None
+    system_message: Optional[str] = None
-    session: list[Message] | None = None
+    session: Optional[list[Message]] = None
-    session_filename: pathlib.Path | None = None
+    session_filename: Optional[pathlib.Path] = None
 
 
 class MyCLI(click.MultiCommand):
     def make_context(
         self,
-        info_name: str | None,
+        info_name: Optional[str],
         args: list[str],
-        parent: click.Context | None = None,
+        parent: Optional[click.Context] = None,
         **extra: Any,
     ) -> click.Context:
         result = super().make_context(info_name, args, parent, obj=Obj(), **extra)

src/chap/session.py

@@ -7,7 +7,7 @@ from __future__ import annotations
 import json
 import pathlib
 from dataclasses import asdict, dataclass
-from typing import cast
+from typing import Union, cast
 
 from typing_extensions import TypedDict
 
@@ -65,11 +65,11 @@ def session_from_json(data: str) -> Session:
     return [Message(**mapping) for mapping in j]
 
 
-def session_from_file(path: pathlib.Path | str) -> Session:
+def session_from_file(path: Union[pathlib.Path, str]) -> Session:
     with open(path, "r", encoding="utf-8") as f:
         return session_from_json(f.read())
 
 
-def session_to_file(session: Session, path: pathlib.Path | str) -> None:
+def session_to_file(session: Session, path: Union[pathlib.Path, str]) -> None:
     with open(path, "w", encoding="utf-8") as f:
         f.write(session_to_json(session))