diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
index 7bec79c..b9d5c42 100644
--- a/.github/workflows/check.yml
+++ b/.github/workflows/check.yml
@@ -22,6 +22,7 @@ jobs:
           - Windows
           - macOS
         py:
+          - 3.10.0-rc.2
           - 3.9
           - 3.8
           - 3.7
@@ -30,7 +31,7 @@ jobs:
       - name: Setup python for tox
         uses: actions/setup-python@v2
         with:
-          python-version: 3.9
+          python-version: 3.10.0-rc.2
       - name: Install tox
         run: python -m pip install tox
       - uses: actions/checkout@v2
@@ -81,10 +82,10 @@ jobs:
           - dev
     steps:
       - uses: actions/checkout@v2
-      - name: Setup Python 3.9
+      - name: Setup Python 3.10.0-rc.2
         uses: actions/setup-python@v2
         with:
-          python-version: 3.9
+          python-version: 3.10.0-rc.2
       - name: Install tox
         run: python -m pip install tox
       - name: Run check for ${{ matrix.tox_env }}
@@ -100,7 +101,7 @@ jobs:
       - name: Setup python to build package
         uses: actions/setup-python@v2
         with:
-          python-version: 3.9
+          python-version: 3.10.0-rc.2
       - name: Install build
         run: python -m pip install build
       - uses: actions/checkout@v2
diff --git a/.gitignore b/.gitignore
index 0579b4b..af111cb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,69 +1,13 @@
-# Byte-compiled / optimized / DLL files
-__pycache__/
-*.py[cod]
-*$py.class
-
-# C extensions
-*.so
-
-# Distribution / packaging
-.Python
-env/
-build/
-develop-eggs/
-dist/
-downloads/
-eggs/
-.eggs/
-lib/
-lib64/
-parts/
-sdist/
-var/
+*.pyc
+*.pyo
+*.swp
+__pycache__
+.eggs
+/src/retype/version.py
+build
+dist
 *.egg-info
-.installed.cfg
-*.egg
-
-# PyInstaller
-#  Usually these files are written by a python script from a template
-#  before PyInstaller builds the exe, so as to inject date/other infos into it.
-*.manifest
-*.spec
-
-# Installer logs
-pip-log.txt
-pip-delete-this-directory.txt
-
-# Unit test / coverage reports
-htmlcov/
 .tox
-.coverage
-.coverage.*
-.cache
-nosetests.xml
-coverage.xml
-*,cover
-.hypothesis/
-
-# Translations
-*.mo
-*.pot
-
-# Django stuff:
-*.log
-
-# Sphinx documentation
-docs/_build/
-
-# PyBuilder
-target/
-
-#Ipython Notebook
-.ipynb_checkpoints
-
-typed-src/
-
+/.*_cache
+.dmypy.json
 pip-wheel-metadata
-.mypy_cache
-
-src/retype/version.py
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index a60c9cd..6fd3dc1 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -1,6 +1,6 @@
 repos:
   - repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v4.0.0
+    rev: v4.0.1
     hooks:
       - id: trailing-whitespace
       - id: end-of-file-fixer
@@ -12,15 +12,15 @@ repos:
       - id: flake8
         additional_dependencies: [ "flake8-bugbear", "flake8-pyi" ]
   - repo: https://github.com/asottile/pyupgrade
-    rev: v2.15.0
+    rev: v2.29.0
     hooks:
       - id: pyupgrade
   - repo: https://github.com/PyCQA/isort
-    rev: 5.8.0
+    rev: 5.9.3
     hooks:
       - id: isort
   - repo: https://github.com/python/black
-    rev: 21.5b1
+    rev: 21.9b0
     hooks:
       - id: black
         args: [ --safe ]
@@ -28,7 +28,8 @@ repos:
     rev: v1.17.0
     hooks:
       - id: setup-cfg-fmt
+        args: ['--max-py-version', '3.10']
   - repo: https://github.com/tox-dev/tox-ini-fmt
-    rev: "0.5.0"
+    rev: "0.5.1"
     hooks:
       - id: tox-ini-fmt
diff --git a/codecov.yml b/codecov.yml
new file mode 100644
index 0000000..5f91842
--- /dev/null
+++ b/codecov.yml
@@ -0,0 +1,6 @@
+coverage:
+  status:
+    patch:
+      default:
+        informational: true
+comment: false
diff --git a/setup.cfg b/setup.cfg
index 209aede..c8fe924 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -21,6 +21,7 @@ classifiers =
     Programming Language :: Python :: 3.7
     Programming Language :: Python :: 3.8
     Programming Language :: Python :: 3.9
+    Programming Language :: Python :: 3.10
     Topic :: Software Development :: Libraries :: Python Modules
     Topic :: Software Development :: Quality Assurance
 keywords = mypy typing typehints type hints pep484 pyi stubs
@@ -31,9 +32,9 @@ project_urls =
 [options]
 packages = find:
 install_requires =
-    click
+    click>=7
     pathspec>=0.5.9,<1
-    typed-ast
+    typed-ast>=1.3
 python_requires = >=3.6
 package_dir =
     =src
@@ -48,8 +49,8 @@ console_scripts =
 
 [options.extras_require]
 testing =
-    pytest>=3.0.0,<6
-    pytest-cov>=2.5.1,<3
+    pytest>=6
+    pytest-cov>=2.5.1
 
 [flake8]
 ignore =
diff --git a/src/retype/__init__.py b/src/retype/__init__.py
index faef8ea..558d45c 100644
--- a/src/retype/__init__.py
+++ b/src/retype/__init__.py
@@ -74,7 +74,7 @@ def retype_file(src, pyi_dir, targets, *, quiet=False, hg=False, flags=None):
     with tokenize.open(src) as src_buffer:
         src_contents = src_buffer.read()
         if src_contents == "":
-            return
+            return None
         src_encoding = src_buffer.encoding
         src_node = lib2to3_parse(src_contents)
     try:
@@ -284,7 +284,7 @@ def _r_functiondef(fun, node, flags):
                 raise ValueError(
                     f"Annotation problem in function {name.value!r}: "
                     + f"{lineno}:{column}: {ve}"
-                )
+                ) from ve
             break
     else:
         raise ValueError(f"Function {name.value!r} not found in source.")
@@ -1005,7 +1005,7 @@ def get_function_signature(fun, *, is_method=False):
             raise ValueError(
                 f"Annotation problem in function {fun.name!r}: "
                 + f"{fun.lineno}:{fun.col_offset + 1}: {exc}"
-            )
+            ) from exc
     copy_type_comments_to_annotations(args)
 
     return args, returns
@@ -1025,8 +1025,10 @@ def parse_signature_type_comment(type_comment):
     """
     try:
         result = ast3.parse(type_comment, "<func_type>", "func_type")
-    except SyntaxError:
-        raise ValueError(f"invalid function signature type comment: {type_comment!r}")
+    except SyntaxError as exc:
+        raise ValueError(
+            f"invalid function signature type comment: {type_comment!r}"
+        ) from exc
 
     assert isinstance(result, ast3.FunctionType)
     if len(result.argtypes) == 1:
@@ -1147,11 +1149,10 @@ def copy_type_comment_to_annotation(arg):
 
 def normalize_strings_to_repr(node):
     """Normalize string leaf nodes to a repr since that is what we generate."""
-    if node.type == token.STRING:
+    if isinstance(node, Leaf) and node.type == token.STRING:
         node.value = repr(ast3.literal_eval(node.value))
     elif isinstance(node, Node):
         node.children = [normalize_strings_to_repr(i) for i in node.children]
-
     return node
 
 
@@ -1518,8 +1519,9 @@ def walk_not_git_ignored(path, keep, extra_ignore):
 )
 
 
-__all__ = (
+__all__ = [
     "__version__",
     "retype_path",
     "retype_file",
-)
+    "ReApplyFlags",
+]
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index a2a7a70..e34aa33 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -6,7 +6,7 @@
 from retype import walk_not_git_ignored
 
 
-@pytest.fixture()  # type: ignore
+@pytest.fixture()
 def build(tmp_path):
     def _build(files):
         for file, content in files.items():
@@ -44,9 +44,7 @@ def _build(files):
 }
 
 
-@pytest.mark.parametrize(  # type: ignore
-    "case", WALK_TESTS.values(), ids=list(WALK_TESTS.keys())
-)
+@pytest.mark.parametrize("case", WALK_TESTS.values(), ids=list(WALK_TESTS.keys()))
 def test_walk(case: Case, build, monkeypatch):
     path = build(case.files)
     dest = path / case.cwd
diff --git a/tests/test_retype.py b/tests/test_retype.py
index 0bbbf73..af732b4 100644
--- a/tests/test_retype.py
+++ b/tests/test_retype.py
@@ -4,7 +4,7 @@
 from contextlib import contextmanager
 from pathlib import Path
 from textwrap import dedent
-from typing import Optional
+from typing import Iterator, Optional
 from unittest import TestCase, main
 
 from typed_ast import ast3
@@ -22,7 +22,7 @@
 
 
 @contextmanager
-def as_cwd(path):
+def as_cwd(path: Path) -> Iterator[None]:
     old = Path.cwd()
     try:
         os.chdir(path)
diff --git a/tox.ini b/tox.ini
index b4557fa..6485bc3 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,5 +1,6 @@
 [tox]
 envlist =
+    py310
     py39
     py38
     py37
@@ -31,6 +32,8 @@ commands =
       --cov-report xml:{toxworkdir}/coverage.{envname}.xml \
       --junitxml {toxworkdir}/junit.{envname}.xml \
       tests {posargs}
+package = wheel
+wheel_build_env = .pkg
 
 [testenv:coverage]
 description = [run locally after tests]: combine coverage data and create report;
@@ -52,6 +55,7 @@ commands =
     coverage html -d {toxworkdir}/htmlcov
     diff-cover --compare-branch {env:DIFF_AGAINST:origin/master} {toxworkdir}/coverage.xml
 depends =
+    py310
     py39
     py38
     py37
@@ -70,7 +74,8 @@ commands =
 description = run the type checker
 skip_install = true
 deps =
-    mypy==0.782
+    mypy==0.910
+    types-typed-ast
 commands =
     mypy types --strict
 
@@ -92,7 +97,7 @@ commands =
 description = check that the long description is valid (need for PyPi)
 skip_install = true
 deps =
-    build>=0.0.4
+    build>=0.5
     twine>=3
 extras =
 commands =
diff --git a/types/src/retype/__init__.pyi b/types/src/retype/__init__.pyi
index 51f0d2f..633cc33 100644
--- a/types/src/retype/__init__.pyi
+++ b/types/src/retype/__init__.pyi
@@ -8,7 +8,6 @@ from typing import (
     Iterator,
     List,
     Optional,
-    Sequence,
     Tuple,
     Type,
     Union,
@@ -17,7 +16,7 @@ from typing import (
 from pathspec import PathSpec
 from typed_ast import ast3
 
-from retype import ReApplyFlags
+from retype import ReApplyFlags  # type: ignore # implicit reexport
 
 _LN = Union[Node, Leaf]
 Callbacks = List[Callable[[], None]]
@@ -109,6 +108,8 @@ def names_already_imported(
 ) -> bool: ...
 def _convert_annotation(ann: ast3.AST) -> _LN: ...
 def convert_annotation(ann: ast3.AST) -> _LN: ...
+def normalize_node(node: _LN) -> _LN: ...
+def normalize_strings_to_repr(node: _LN) -> _LN: ...
 def serialize_attribute(attr: ast3.AST) -> str: ...
 def reapply(
     ast_node: ast3.AST, lib2to3_node: Node, flags: ReApplyFlags
@@ -126,7 +127,7 @@ def retype_file(
     quiet: bool = ...,
     hg: bool = ...,
     flags: Optional[ReApplyFlags] = ...,
-) -> Path: ...
+) -> Optional[Path]: ...
 def retype_path(
     src: Path,
     pyi_dir: Path,
@@ -165,7 +166,7 @@ def _c_str(s: ast3.Str) -> Leaf: ...
 def _c_num(n: ast3.Num) -> Leaf: ...
 def _c_index(index: ast3.Index) -> _LN: ...
 def _c_tuple(tup: ast3.Tuple) -> Node: ...
-def _c_attribute(attr: ast3.Attribute) -> Leaf: ...
+def _c_attribute(attr: ast3.Attribute) -> Node: ...
 def _c_call(call: ast3.Call) -> Node: ...
 def _c_keyword(kwarg: ast3.keyword) -> Node: ...
 def _c_list(l: ast3.List) -> Node: ...
diff --git a/types/tests/test_discovery.pyi b/types/tests/test_discovery.pyi
index b09fcb1..fd4de87 100644
--- a/types/tests/test_discovery.pyi
+++ b/types/tests/test_discovery.pyi
@@ -5,11 +5,14 @@ from _pytest.monkeypatch import MonkeyPatch
 
 Case: NamedTuple = ...
 
-WALK_TESTS: Dict[str, Case]
+WALK_TESTS: Dict[str, Case]  # type: ignore # retype does not support merging class variant namedtuple with inline one
 
 def build(tmp_path: Path) -> Callable[[Dict[str, str]], Path]:
     def _build(files: Dict[str, str]) -> Path: ...
+    return _build
 
 def test_walk(
-    case: Case, build: Callable[[Dict[str, str]], Path], monkeypatch: MonkeyPatch
+    case: Case,  # type: ignore # retype does not support merging class variant namedtuple with inline one
+    build: Callable[[Dict[str, str]], Path],
+    monkeypatch: MonkeyPatch,
 ) -> None: ...
diff --git a/types/tests/test_retype.pyi b/types/tests/test_retype.pyi
index 3dd30a9..09cb59d 100644
--- a/types/tests/test_retype.pyi
+++ b/types/tests/test_retype.pyi
@@ -1,7 +1,10 @@
 from lib2to3.pytree import Leaf, Node
+from pathlib import Path
 from typing import Tuple, Type, TypeVar, Union
 from unittest import TestCase
 
+from typed_ast import ast3
+
 _E = TypeVar("_E", bound=Exception)
 _LN = Union[Node, Leaf]
 
@@ -13,7 +16,7 @@ class RetypeTestCase(TestCase):
         *,
         incremental: bool = ...,
         replace_any: bool = ...,
-    ) -> Tuple[_LN, _LN]: ...
+    ) -> Tuple[ast3.Module, Node]: ...
     def assertReapply(
         self,
         pyi_txt: str,
@@ -41,3 +44,6 @@ class RetypeTestCase(TestCase):
         incremental: bool = ...,
         replace_any: bool = ...,
     ) -> _E: ...
+
+def test_can_run_against_current_directory(tmp_path: Path) -> None: ...
+def test_does_not_error_on_empty_file(tmp_path: Path) -> None: ...