Migrate from mypy to ty as a type checker (#1731)

* Migrate from mypy to ty as a type checker

* Eliminated all the ty ignore rules other than the one for unresolved attributes

* Add unit test for uncovered line

Author: tleonhardt

.github/workflows/typecheck.yml

@@ -32,4 +32,4 @@ jobs:
           python-version: ${{ matrix.python-version }}
 
       - name: Check typing
-        run: uv run mypy .
+        run: uv run ty check

Makefile

@@ -18,8 +18,8 @@ check: ## Run code quality tools.
 	@uv lock --locked
 	@echo "🚀 Auto-formatting/Linting code and documentation: Running prek"
 	@uv run prek run -a
-	@echo "🚀 Static type checking: Running mypy"
-	@uv run mypy
+	@echo "🚀 Static type checking: Running ty"
+	@uv run ty check
 
 .PHONY: format
 format: ## Perform ruff formatting
@@ -31,7 +31,7 @@ lint: ## Perform ruff linting
 
 .PHONY: typecheck
 typecheck: ## Perform type checking
-	@uv run mypy
+	@uv run ty check
 
 .PHONY: test
 test: ## Test the code with pytest.
@@ -76,7 +76,7 @@ publish: validate-tag build ## Publish a release to PyPI, uses token from ~/.pyp
 # Define variables for files/directories to clean
 BUILD_DIRS = build dist *.egg-info
 DOC_DIRS = build
-MYPY_DIRS = .mypy_cache dmypy.json dmypy.sock
+TY_DIRS = .ty_cache .red_knot_cache
 TEST_DIRS = .cache .pytest_cache htmlcov
 TEST_FILES = .coverage coverage.xml
 
@@ -90,10 +90,10 @@ clean-docs: ## Clean documentation artifacts
 	@echo "🚀 Removing documentation artifacts"
 	@uv run python -c "import shutil; import os; [shutil.rmtree(d, ignore_errors=True) for d in '$(DOC_DIRS)'.split() if os.path.isdir(d)]"
 
-.PHONY: clean-mypy
-clean-mypy: ## Clean mypy artifacts
-	@echo "🚀 Removing mypy artifacts"
-	@uv run python -c "import shutil; import os; [shutil.rmtree(d, ignore_errors=True) for d in '$(MYPY_DIRS)'.split() if os.path.isdir(d)]"
+.PHONY: clean-ty
+clean-ty: ## Clean ty artifacts
+	@echo "🚀 Removing ty artifacts"
+	@uv run python -c "import shutil; import os; [shutil.rmtree(d, ignore_errors=True) for d in '$(TY_DIRS)'.split() if os.path.isdir(d)]"
 
 .PHONY: clean-pycache
 clean-pycache: ## Clean pycache artifacts
@@ -112,7 +112,7 @@ clean-test: ## Clean test artifacts
 	@uv run python -c "from pathlib import Path; [Path(f).unlink(missing_ok=True) for f in '$(TEST_FILES)'.split()]"
 
 .PHONY: clean
-clean: clean-build clean-docs clean-mypy clean-pycache clean-ruff clean-test ## Clean all artifacts
+clean: clean-build clean-docs clean-ty clean-pycache clean-ruff clean-test ## Clean all artifacts
 	@echo "🚀 Cleaned all artifacts"
 
 .PHONY: help

cmd2/annotated.py

@@ -708,10 +708,10 @@ def __init__(self, *args: Any, container_factory: Callable[[list[Any]], Any] | N
 
     def __call__(
         self,
-        _parser: argparse.ArgumentParser,
+        parser: argparse.ArgumentParser,  # noqa: ARG002
         namespace: argparse.Namespace,
         values: Any,
-        _option_string: str | None = None,
+        option_string: str | None = None,  # noqa: ARG002
     ) -> None:
         result = values
         if self._container_factory is not None and isinstance(values, list):
@@ -879,7 +879,7 @@ def _resolve_union(
         raise TypeError(f"Union type {type_names} is ambiguous for auto-resolution.")
 
     parts = [_resolve_base_type(member, allow_unknown_entry=allow_unknown_entry) for member in non_none]
-    # Every part is an Enum (guarded above), so each has a converter; the None-filter keeps mypy happy.
+    # Every part is an Enum (guarded above), so each has a converter; the None-filter keeps the type checker happy.
     converters = [part.converter for part in parts if part.converter is not None]
     choices = _dedupe_choices(choice for part in parts for choice in (part.choices or []))
 
@@ -2189,7 +2189,7 @@ def _find_argument_block(hint: Any) -> type[ArgumentBlock] | None:
     return None
 
 
-def _init_field_names(dc_type: type) -> list[str]:
+def _init_field_names(dc_type: Any) -> list[str]:
     """Names of a dataclass's ``init`` fields in definition order (the flat argument names of a block)."""
     return [f.name for f in fields(dc_type) if f.init]
 
@@ -3113,6 +3113,9 @@ def cmd_wrapper(*args: Any, **kwargs: Any) -> bool | None:
             except SystemExit as exc:
                 raise Cmd2ArgparseError from exc
 
+            if ns is None:
+                raise ValueError("ns is None")
+
             setattr(ns, constants.NS_ATTR_STATEMENT, statement)
             handler = getattr(ns, constants.NS_ATTR_SUBCOMMAND_FUNC, None)
             if base_command and handler is not None:

cmd2/argparse_utils.py

@@ -747,8 +747,8 @@ def __init__(
         super().__init__(
             prog=prog,
             usage=usage,
-            description=description,  # type: ignore[arg-type]
-            epilog=epilog,  # type: ignore[arg-type]
+            description=description,  # type: ignore[arg-type, ty:invalid-argument-type]
+            epilog=epilog,  # type: ignore[arg-type, ty:invalid-argument-type]
             parents=parents,
             formatter_class=formatter_class,
             prefix_chars=prefix_chars,
@@ -772,15 +772,15 @@ def __init__(
         self.description: HelpContent | None  # type: ignore[assignment]
         self.epilog: HelpContent | None  # type: ignore[assignment]
 
-    def print_usage(self, file: IO[str] | None = None) -> None:  # type:ignore[override]
+    def print_usage(self, file: IO[str] | None = None) -> None:  # type: ignore[override, ty:invalid-method-override]
         """Override to ensure the formatter is aware of the target file."""
         if file is None:
             file = self._thread_locals.current_output_file
 
         with self.output_to(file):
             super().print_usage(file)
 
-    def print_help(self, file: IO[str] | None = None) -> None:  # type:ignore[override]
+    def print_help(self, file: IO[str] | None = None) -> None:  # type: ignore[override, ty:invalid-method-override]
         """Override to ensure the formatter is aware of the target file."""
         if file is None:
             file = self._thread_locals.current_output_file
@@ -831,7 +831,7 @@ def _build_subparsers_prog_prefix(self, positionals: list[argparse.Action]) -> s
         temp_parser = Cmd2ArgumentParser(
             prog=self.prog,
             usage=None,
-            formatter_class=self.formatter_class,
+            formatter_class=cast(type[Cmd2HelpFormatter], self.formatter_class),
             add_help=False,
         )
 
@@ -1037,7 +1037,8 @@ def error(self, message: str) -> NoReturn:
 
     def _get_formatter(self, *_args: Any, **_kwargs: Any) -> Cmd2HelpFormatter:
         """Override with customizations for Cmd2HelpFormatter."""
-        return self.formatter_class(prog=self.prog, file=self._thread_locals.current_output_file)
+        formatter_class = cast(type[Cmd2HelpFormatter], self.formatter_class)
+        return formatter_class(prog=self.prog, file=self._thread_locals.current_output_file)
 
     def format_help(self, *args: Any, **kwargs: Any) -> str:
         """Override to add a newline."""

cmd2/cmd2.py

@@ -849,7 +849,7 @@ def _autoload_commands(self) -> None:
         all_commandset_defs = CommandSet.__subclasses__()
         existing_commandset_types = [type(command_set) for command_set in self._installed_command_sets]
 
-        def load_commandset_by_type(commandset_types: list[type[CommandSet[Any]]]) -> None:
+        def load_commandset_by_type(commandset_types: Sequence[type[CommandSet[Any]]]) -> None:
             for cmdset_type in commandset_types:
                 # check if the type has sub-classes. We will only auto-load leaf class types.
                 subclasses = cmdset_type.__subclasses__()
@@ -2547,11 +2547,11 @@ def _perform_completion(
                             completer.complete, tokens=raw_tokens[1:] if spec.preserve_quotes else tokens[1:], cmd_set=cmd_set
                         )
                     else:
-                        completer_func = self.completedefault  # type: ignore[assignment]
+                        completer_func = self.completedefault  # type: ignore[assignment, ty:invalid-assignment]
 
             # Not a recognized macro or command
             else:
-                completer_func = self.completedefault  # type: ignore[assignment]
+                completer_func = self.completedefault  # type: ignore[assignment, ty:invalid-assignment]
 
         # Otherwise we are completing the command token or performing custom completion
         else:
@@ -2968,7 +2968,7 @@ def onecmd_plus_hooks(
                 with self.sigint_protection:
                     if py_bridge_call:
                         # Start saving command's stdout at this point
-                        self.stdout.pause_storage = False  # type: ignore[attr-defined]
+                        self.stdout.pause_storage = False  # type: ignore[attr-defined, ty:invalid-assignment]
 
                     redir_saved_state = self._redirect_output(statement)
 
@@ -3007,7 +3007,7 @@ def onecmd_plus_hooks(
 
                     if py_bridge_call:
                         # Stop saving command's stdout before command finalization hooks run
-                        self.stdout.pause_storage = True  # type: ignore[attr-defined]
+                        self.stdout.pause_storage = True  # type: ignore[attr-defined, ty:invalid-assignment]
         except (SkipPostcommandHooks, EmptyStatement):
             # Don't do anything, but do allow command finalization hooks to run
             pass
@@ -3512,7 +3512,7 @@ def _read_raw_input(
                     self.active_session = self.main_session
 
         # We're not at a terminal, so we're likely reading from a file or a pipe.
-        prompt_obj = prompt() if callable(prompt) else prompt
+        prompt_obj = prompt if isinstance(prompt, (ANSI, str)) else prompt()
         prompt_str = prompt_obj.value if isinstance(prompt_obj, ANSI) else prompt_obj
 
         # If this is an interactive pipe, then display the prompt first
@@ -3800,7 +3800,7 @@ def _build_alias_parser() -> Cmd2ArgumentParser:
             "An alias is a command that enables replacement of a word by another string.",
         )
         alias_parser = argparse_utils.DEFAULT_ARGUMENT_PARSER(description=alias_description)
-        alias_parser.epilog = TextGroup(
+        alias_parser.epilog = TextGroup(  # type: ignore[assignment, ty:invalid-assignment]
             "See Also",
             "macro",
         )
@@ -3832,7 +3832,7 @@ def _build_alias_create_parser(cls) -> Cmd2ArgumentParser:
                 "for the actual command the alias resolves to."
             ),
         )
-        alias_create_parser.epilog = TextGroup("Notes", alias_create_notes)
+        alias_create_parser.epilog = TextGroup("Notes", alias_create_notes)  # type: ignore[assignment, ty:invalid-assignment]
 
         # Add arguments
         alias_create_parser.add_argument("name", help="name of this alias")
@@ -4014,7 +4014,7 @@ def _build_macro_parser() -> Cmd2ArgumentParser:
             "A macro is similar to an alias, but it can contain argument placeholders.",
         )
         macro_parser = argparse_utils.DEFAULT_ARGUMENT_PARSER(description=macro_description)
-        macro_parser.epilog = TextGroup(
+        macro_parser.epilog = TextGroup(  # type: ignore[assignment, ty:invalid-assignment]
             "See Also",
             "alias",
         )
@@ -4077,7 +4077,7 @@ def _build_macro_create_parser(cls) -> Cmd2ArgumentParser:
                 "This default behavior changes if custom completion for macro arguments has been implemented."
             ),
         )
-        macro_create_parser.epilog = TextGroup("Notes", macro_create_notes)
+        macro_create_parser.epilog = TextGroup("Notes", macro_create_notes)  # type: ignore[assignment, ty:invalid-assignment]
 
         # Add arguments
         macro_create_parser.add_argument("name", help="name of this macro")
@@ -4572,7 +4572,7 @@ def do_shortcuts(self, _: argparse.Namespace) -> None:
     @staticmethod
     def _build__eof_parser() -> Cmd2ArgumentParser:
         _eof_parser = argparse_utils.DEFAULT_ARGUMENT_PARSER(description="Called when Ctrl-D is pressed.")
-        _eof_parser.epilog = TextGroup(
+        _eof_parser.epilog = TextGroup(  # type: ignore[assignment, ty:invalid-assignment]
             "Note",
             "This command is for internal use and is not intended to be called from the command line.",
         )
@@ -5032,7 +5032,7 @@ def py_quit() -> None:
             # Check if we are running Python code
             if py_code_to_run:
                 try:  # noqa: SIM105
-                    interp.runcode(py_code_to_run)  # type: ignore[arg-type]
+                    interp.runcode(py_code_to_run)  # type: ignore[arg-type, ty:invalid-argument-type]
                 except BaseException:  # noqa: BLE001, S110
                     # We don't care about any exception that happened in the Python code
                     pass
@@ -5418,11 +5418,11 @@ def _initialize_history(self, hist_file: str) -> None:
         try:
             import lzma as decompress_lib
 
-            decompress_exceptions: tuple[type[Exception]] = (decompress_lib.LZMAError,)
+            decompress_exceptions: tuple[type[Exception], ...] = (decompress_lib.LZMAError,)
         except ModuleNotFoundError:  # pragma: no cover
             import bz2 as decompress_lib  # type: ignore[no-redef]
 
-            decompress_exceptions: tuple[type[Exception]] = (OSError, ValueError)  # type: ignore[no-redef]
+            decompress_exceptions: tuple[type[Exception], ...] = (OSError, ValueError)  # type: ignore[no-redef]
 
         try:
             history_json = decompress_lib.decompress(compressed_bytes).decode(encoding="utf-8")
@@ -5471,7 +5471,7 @@ def _persist_history(self) -> None:
     def _build_edit_parser(cls) -> Cmd2ArgumentParser:
         edit_description = "Run a text editor and optionally open a file with it."
         edit_parser = argparse_utils.DEFAULT_ARGUMENT_PARSER(description=edit_description)
-        edit_parser.epilog = TextGroup(
+        edit_parser.epilog = TextGroup(  # type: ignore[assignment, ty:invalid-assignment]
             "Note",
             Text.assemble(
                 "To set a new editor, run: ",
@@ -5593,7 +5593,7 @@ def _build__relative_run_script_parser(cls) -> Cmd2ArgumentParser:
         _relative_run_script_parser = cls._build_base_run_script_parser()
 
         # Append to existing description
-        _relative_run_script_parser.description = Group(
+        _relative_run_script_parser.description = Group(  # type: ignore[assignment, ty:invalid-assignment]
             cast(Group, _relative_run_script_parser.description),
             "\n",
             (
@@ -5602,7 +5602,7 @@ def _build__relative_run_script_parser(cls) -> Cmd2ArgumentParser:
             ),
         )
 
-        _relative_run_script_parser.epilog = TextGroup(
+        _relative_run_script_parser.epilog = TextGroup(  # type: ignore[assignment, ty:invalid-assignment]
             "Note",
             "This command is intended to be used from within a text script.",
         )

cmd2/decorators.py

@@ -310,7 +310,7 @@ def arg_decorator(func: ArgparseCommandFunc[CmdOrSetT]) -> RawCommandFunc[CmdOrS
         :return: Function that takes raw input and converts to an argparse Namespace to passed to the wrapped function.
         """
 
-        @functools.wraps(func)
+        @functools.wraps(func)  # type: ignore[arg-type, ty:invalid-argument-type]
         def cmd_wrapper(*args: Any, **kwargs: Any) -> bool | None:
             """Command function wrapper which translates command line into argparse Namespace and call actual command function.
 
@@ -345,9 +345,9 @@ def cmd_wrapper(*args: Any, **kwargs: Any) -> bool | None:
                 parsing_results: tuple[argparse.Namespace] | tuple[argparse.Namespace, list[str]]
                 with arg_parser.output_to(cmd_app.stdout):
                     if with_unknown_args:
-                        parsing_results = arg_parser.parse_known_args(command_arg_list, initial_namespace)
+                        parsing_results = arg_parser.parse_known_args(command_arg_list, initial_namespace)  # type: ignore[assignment, ty:invalid-assignment]
                     else:
-                        parsing_results = (arg_parser.parse_args(command_arg_list, initial_namespace),)
+                        parsing_results = (arg_parser.parse_args(command_arg_list, initial_namespace),)  # type: ignore[assignment, ty:invalid-assignment]
             except SystemExit as exc:
                 raise Cmd2ArgparseError from exc
 

cmd2/pt_utils.py

@@ -148,7 +148,7 @@ def __init__(
         self._cmd_app = cmd_app
         self.custom_settings = custom_settings
 
-    def get_completions(self, document: Document, _complete_event: object) -> Iterable[Completion]:
+    def get_completions(self, document: Document, complete_event: object) -> Iterable[Completion]:  # noqa: ARG002
         """Get completions for the current input."""
         # Find the beginning of the current word based on delimiters
         line = document.text

cmd2/rich_utils.py

@@ -105,7 +105,7 @@ def __repr__(self) -> str:
 
 
 # Controls when ANSI style sequences are allowed in output
-ALLOW_STYLE = AllowStyle.TERMINAL
+ALLOW_STYLE: AllowStyle = AllowStyle.TERMINAL
 
 
 class Cmd2HelpFormatter(RichHelpFormatter):

pyproject.toml

@@ -40,12 +40,12 @@ dev = [
     "codecov>=2.1",
     "ipython>=8.23",
     "mkdocstrings[python]>=1",
-    "mypy>=1.13",
     "prek>=0.3.5",
     "pytest>=8.1.1",
     "pytest-cov>=5",
     "pytest-mock>=3.14.1",
     "ruff>=0.14.10",
+    "ty>=0.0.73",
     "uv-publish>=1.3",
     "zensical>=0.0.17",
 ]
@@ -63,33 +63,7 @@ test = [
     "pytest-cov>=5",
     "pytest-mock>=3.14.1",
 ]
-validate = ["mypy>=1.13", "ruff>=0.14.10", "types-setuptools>=80.8.0"]
-
-[tool.mypy]
-disallow_incomplete_defs = true
-disallow_untyped_calls = true
-disallow_untyped_defs = true
-exclude = [
-    "^.git/",
-    "^.venv/",
-    "^build/",        # .build directory
-    "^docs/",         # docs directory
-    "^dist/",
-    "^examples/",     # examples directory
-    "^noxfile\\.py$", # nox config file
-    "setup\\.py$",    # any files named setup.py
-    "^site/",
-    "^tests/",        # tests directory
-]
-files = ['.']
-show_column_numbers = true
-show_error_codes = true
-show_error_context = true
-strict = true
-warn_redundant_casts = true
-warn_return_any = true
-warn_unreachable = true
-warn_unused_ignores = false
+validate = ["ruff>=0.14.10", "ty>=0.0.73", "types-setuptools>=80.8.0"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]

ruff.toml

@@ -7,15 +7,16 @@ exclude = [
     ".git-rewrite",
     ".hg",
     ".ipynb_checkpoints",
-    ".mypy_cache",
     ".nox",
     ".pants.d",
     ".pyenv",
     ".pytest_cache",
     ".pytype",
+    ".red_knot_cache",
     ".ruff_cache",
     ".svn",
     ".tox",
+    ".ty_cache",
     ".venv",
     ".vscode",
     "__pypackages__",