diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 5469b3a..75bcba0 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -34,7 +34,7 @@ jobs:
         run: "python -m tox"
 
       - name: "Report to coveralls"
-        # coverage is only created in the py39 environment
+        # coverage is only created in the py314 environment
         # --service=github is a workaround for bug
         # https://github.com/coveralls-clients/coveralls-python/issues/251
         if: "matrix.python-version == '3.14'"
diff --git a/.gitignore b/.gitignore
index b250aa7..456e39d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -10,7 +10,7 @@ pip-wheel-metadata
 
 # Virtualenv
 /env/
-/src/
+/.venv/
 
 # Unit test / coverage reports
 .cache
@@ -20,4 +20,8 @@ htmlcov
 .tox
 
 # Sphinx documentation
+/doc/_build/
 /doc/build/
+
+# Type checkers
+.mypy_cache/
diff --git a/CHANGES.txt b/CHANGES.txt
index 80ea5d5..661ce8c 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1,8 +1,12 @@
 CHANGES
 *******
 
-0.3 (unreleased)
-----------------
+1.0.0 (unreleased)
+------------------
+
+- Skip importing packages in scan() since they're already imported in walk_packages().
+
+- Add type annotations.
 
 - Add support for Python 3.10 - 3.14.
 
@@ -12,6 +16,10 @@ CHANGES
 
 - Use GitHub Actions for CI.
 
+- Add tests for 100% coverage.
+
+- Update docs.
+
 
 0.2 (2020-01-29)
 ----------------
diff --git a/README.rst b/README.rst
index f14e91b..955e4a6 100644
--- a/README.rst
+++ b/README.rst
@@ -20,4 +20,4 @@ import a package and its sub-modules and sub-packages.
 
 Documentation_.
 
-.. _Documentation: http://importscan.readthedocs.org
+.. _Documentation: https://importscan.readthedocs.org
diff --git a/develop_requirements.txt b/develop_requirements.txt
index e076727..68e0793 100644
--- a/develop_requirements.txt
+++ b/develop_requirements.txt
@@ -1,11 +1,8 @@
 # development
--e '.[test,coverage,lint]'
+-e '.[test,coverage,lint,docs,mypy,pyright]'
 pre-commit
 tox >= 4
 radon
 
-# documentation
-sphinx
-
 # releaser
 zest.releaser[recommended]
diff --git a/doc/_build/doctest/output.txt b/doc/_build/doctest/output.txt
new file mode 100644
index 0000000..358007f
--- /dev/null
+++ b/doc/_build/doctest/output.txt
@@ -0,0 +1,9 @@
+Results of doctest builder run on 2026-08-07 09:26:02
+=====================================================
+
+Doctest summary
+===============
+    0 tests
+    0 failures in tests
+    0 failures in setup code
+    0 failures in cleanup code
diff --git a/doc/_build/doctrees/__intersphinx_cache__/bowerstatic_objects.inv b/doc/_build/doctrees/__intersphinx_cache__/bowerstatic_objects.inv
new file mode 100644
index 0000000..bad868b
Binary files /dev/null and b/doc/_build/doctrees/__intersphinx_cache__/bowerstatic_objects.inv differ
diff --git a/doc/_build/doctrees/__intersphinx_cache__/reg_objects.inv b/doc/_build/doctrees/__intersphinx_cache__/reg_objects.inv
new file mode 100644
index 0000000..1b57648
Binary files /dev/null and b/doc/_build/doctrees/__intersphinx_cache__/reg_objects.inv differ
diff --git a/doc/_build/doctrees/api.doctree b/doc/_build/doctrees/api.doctree
new file mode 100644
index 0000000..f7a4b53
Binary files /dev/null and b/doc/_build/doctrees/api.doctree differ
diff --git a/doc/_build/doctrees/changes.doctree b/doc/_build/doctrees/changes.doctree
new file mode 100644
index 0000000..3b016c9
Binary files /dev/null and b/doc/_build/doctrees/changes.doctree differ
diff --git a/doc/_build/doctrees/developing.doctree b/doc/_build/doctrees/developing.doctree
new file mode 100644
index 0000000..4992a69
Binary files /dev/null and b/doc/_build/doctrees/developing.doctree differ
diff --git a/doc/_build/doctrees/environment.pickle b/doc/_build/doctrees/environment.pickle
new file mode 100644
index 0000000..028b509
Binary files /dev/null and b/doc/_build/doctrees/environment.pickle differ
diff --git a/doc/_build/doctrees/index.doctree b/doc/_build/doctrees/index.doctree
new file mode 100644
index 0000000..9751228
Binary files /dev/null and b/doc/_build/doctrees/index.doctree differ
diff --git a/doc/conf.py b/doc/conf.py
index 8f723d2..701b690 100644
--- a/doc/conf.py
+++ b/doc/conf.py
@@ -10,7 +10,7 @@
 # All configuration values have a default; values that are commented out
 # serve to show the default.
 
-import pkg_resources
+from importlib import metadata
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -24,16 +24,20 @@
 
 # Add any Sphinx extension module names here, as strings. They can be extensions
 # coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = ["sphinx.ext.autodoc", "sphinx.ext.intersphinx"]
+extensions = [
+    "sphinx.ext.autodoc",
+    "sphinx.ext.intersphinx",
+    "sphinx.ext.doctest",
+]
 
 autoclass_content = "both"
 
 autodoc_member_order = "groupwise"
 
 intersphinx_mapping = {
-    "reg": ("http://reg.readthedocs.io/en/latest", None),
-    "webob": ("http://docs.webob.org/en/latest", None),
-    "bowerstatic": ("http://bowerstatic.readthedocs.io/en/latest", None),
+    "reg": ("https://reg.readthedocs.io/en/latest", None),
+    "webob": ("https://docs.pylonsproject.org/projects/webob/en/latest", None),
+    "bowerstatic": ("https://bowerstatic.readthedocs.io/en/latest", None),
 }
 
 # Add any paths that contain templates here, relative to this directory.
@@ -60,7 +64,28 @@
 # built documents.
 #
 # The short X.Y version.
-version = pkg_resources.get_distribution("importscan").version
+try:
+    version = metadata.version("importscan")
+except metadata.PackageNotFoundError:
+    # Fallback for ReadTheDocs and other environments where the package isn't installed
+    # Try to get version from pyproject.toml
+    import os
+    import re
+
+    try:
+        pyproject_path = os.path.join(
+            os.path.dirname(__file__), "..", "pyproject.toml"
+        )
+        with open(pyproject_path) as f:
+            content = f.read()
+        # Simple regex to extract version
+        version_match = re.search(r'version\s*=\s*["\']([^"\']+)["\']', content)
+        if version_match:
+            version = version_match.group(1)
+        else:
+            version = "0.0.0"
+    except (FileNotFoundError, Exception):
+        version = "0.0.0"
 # The full version, including alpha/beta/rc tags.
 release = version
 
@@ -69,7 +94,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+# language = None
 
 # There are two options for replacing |today|: either, you set today to some
 # non-false value, then it is used:
@@ -82,7 +107,7 @@
 exclude_patterns = ["_build"]
 
 # The reST default role (used for this markup: `text`) to use for all
-# documents.
+# documents.n
 # default_role = None
 
 # If true, '()' will be appended to :func: etc. cross-reference text.
@@ -142,7 +167,7 @@
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,
 # so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = []
+html_static_path: list[str] = []
 
 # Add any extra paths that contain custom files (such as robots.txt or
 # .htaccess) here, relative to this directory. These files are copied
@@ -209,7 +234,7 @@
 
 # -- Options for LaTeX output ---------------------------------------------
 
-latex_elements = {
+latex_elements: dict[str, str] = {
     # The paper size ('letterpaper' or 'a4paper').
     # 'papersize': 'letterpaper',
     # The font size ('10pt', '11pt' or '12pt').
@@ -297,4 +322,4 @@
 
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {"https://docs.python.org/": None}
+# intersphinx_mapping = {"https://docs.python.org/": None}
diff --git a/doc/developing.rst b/doc/developing.rst
index b235452..cea7200 100644
--- a/doc/developing.rst
+++ b/doc/developing.rst
@@ -8,7 +8,7 @@ Install Importscan for development
 
 Clone Importscan from github::
 
-  $ git clone git@github.com:faassen/importscan.git
+  $ git clone git@github.com:morepath/importscan.git
 
 If this doesn't work and you get an error 'Permission denied (publickey)',
 you need to upload your ssh public key to github_.
@@ -21,15 +21,11 @@ Make sure you have virtualenv_ installed.
 
 Create a new virtualenv for Python 3 inside the importscan directory::
 
-  $ virtualenv -p python3 env/py3
+  $ python -m venv --upgrade-deps .venv
 
 Activate the virtualenv::
 
-  $ source env/py3/bin/activate
-
-Make sure you have recent setuptools and pip installed::
-
-  $ pip install -U setuptools pip
+  $ source .venv/bin/activate
 
 Install the various dependencies and development tools from
 develop_requirements.txt::
@@ -42,9 +38,8 @@ For upgrading the requirements just run the command again.
 
    The following commands work only if you have the virtualenv activated.
 
-.. _github: https://help.github.com/articles/generating-an-ssh-key
-
-.. _virtualenv: https://pypi.python.org/pypi/virtualenv
+.. _github: https://docs.github.com/en/authentication/connecting-to-github-with-ssh
+.. _virtualenv: https://pypi.org/project/virtualenv
 
 Install pre-commit hook for Black integration
 ---------------------------------------------
@@ -54,7 +49,7 @@ install the `pre-commit hook`_ for Black integration before committing::
 
   $ pre-commit install
 
-.. _`pre-commit hook`: https://black.readthedocs.io/en/stable/version_control_integration.html
+.. _`pre-commit hook`: https://black.readthedocs.io/en/stable/integrations/source_version_control.html
 
 Running the tests
 -----------------
@@ -71,7 +66,7 @@ You can then point your web browser to the ``htmlcov/index.html`` file
 in the project directory and click on modules to see detailed coverage
 information.
 
-.. _`py.test`: http://pytest.org/latest/
+.. _`py.test`: https://pytest.org/latest/
 
 Black
 -----
@@ -115,11 +110,11 @@ To also show cyclomatic complexity, use this command::
 
   $ flake8 --max-complexity=10 importscan
 
-.. _flake8: https://pypi.python.org/pypi/flake8
+.. _flake8: https://pypi.org/project/flake8
 
-.. _pyflakes: https://pypi.python.org/pypi/pyflakes
+.. _pyflakes: https://pypi.org/project/pyflakes
 
-.. _pep8: http://www.python.org/dev/peps/pep-0008/
+.. _pep8: https://peps.python.org/pep-0008
 
 .. _`cyclomatic complexity`: https://en.wikipedia.org/wiki/Cyclomatic_complexity
 
@@ -151,4 +146,4 @@ You can also specify a test environment to run e.g.::
   $ tox -e lint
   $ tox -e coverage
 
-.. _pyenv: https://github.com/yyuu/pyenv
+.. _pyenv: https://github.com/pyenv/pyenv
diff --git a/importscan/scan.py b/importscan/scan.py
index f081af5..424607c 100644
--- a/importscan/scan.py
+++ b/importscan/scan.py
@@ -2,13 +2,14 @@
 
 import sys
 from pkgutil import iter_modules
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, cast
 
 if TYPE_CHECKING:
     from collections.abc import Callable, Generator, Iterable
     from importlib.abc import Loader
     from types import ModuleType
     from typing_extensions import TypeIs
+
     from importscan.types import IgnoreModule, ModuleInfo, StrOrBytesPath
 
 
@@ -119,23 +120,26 @@ def handle_error(name, e):
         #        into iter_modules for submodules/subpackages. There's also
         #        the additional issue that not all finders will implement the
         #        non-standard iter_modules method, but without it there's
-        #        no way to list all of the modules. Also since walk_packages
-        #        already imports all of the packages, why are we importing
-        #        them again here? Shouldn't we only import modules here?
-        #        Also why do we do only use `import_module` here, but not
-        #        in `walk_packages`? Doesn't that mean that the additional
-        #        check in `import_module` doesn't do anything for packages?
-        loader = importer.find_spec(modname).loader  # type: ignore
+        #        no way to list all of the modules.
+        #
+        # Note: Packages are already imported in walk_packages() to access
+        # their __path__ for recursion and have already been error-checked.
+        # Only modules need to be imported here.
+        if ispkg:
+            continue
+
+        spec = importer.find_spec(modname, None)
+        loader = spec.loader if spec else None
         assert loader is not None
 
         try:
             import_module(modname, loader, handle_error)
         finally:
             if hasattr(loader, "file") and hasattr(
-                loader.file,  # pyright: ignore[reportAttributeAccessIssue]
+                getattr(loader, "file"),
                 "close",
             ):
-                loader.file.close()  # pyright: ignore[reportAttributeAccessIssue]
+                getattr(loader, "file").close()
 
 
 def import_module(
@@ -143,13 +147,17 @@ def import_module(
     loader: Loader,
     handle_error: Callable[[str, Exception], object] | None,
 ) -> None:
-    get_filename = getattr(loader, "get_filename", None)
+    get_filename: Callable[..., str] | None = getattr(
+        loader, "get_filename", None
+    )
     if get_filename is None:
         get_filename = loader._get_filename  # type: ignore[attr-defined]
     try:
-        fn = get_filename(modname)
+        fn: str = cast(
+            str, get_filename(modname)  # pyright: ignore[reportOptionalCall]
+        )
     except TypeError:
-        fn = get_filename()
+        fn = cast(str, get_filename())  # pyright: ignore[reportOptionalCall]
     # only scan non-orphaned source files and package directories
     if fn.endswith((".pyc", ".pyo", "$py.class")):
         return
diff --git a/importscan/tests/fixtures/importerror_pkg/__init__.py b/importscan/tests/fixtures/importerror_pkg/__init__.py
new file mode 100644
index 0000000..c51def1
--- /dev/null
+++ b/importscan/tests/fixtures/importerror_pkg/__init__.py
@@ -0,0 +1 @@
+# pkg
diff --git a/importscan/tests/fixtures/importerror_pkg/sub/__init__.py b/importscan/tests/fixtures/importerror_pkg/sub/__init__.py
new file mode 100644
index 0000000..abe851f
--- /dev/null
+++ b/importscan/tests/fixtures/importerror_pkg/sub/__init__.py
@@ -0,0 +1 @@
+raise ImportError("cannot import sub")
diff --git a/importscan/tests/fixtures/importerror_pkg_handle_error/__init__.py b/importscan/tests/fixtures/importerror_pkg_handle_error/__init__.py
new file mode 100644
index 0000000..c51def1
--- /dev/null
+++ b/importscan/tests/fixtures/importerror_pkg_handle_error/__init__.py
@@ -0,0 +1 @@
+# pkg
diff --git a/importscan/tests/fixtures/importerror_pkg_handle_error/sub/__init__.py b/importscan/tests/fixtures/importerror_pkg_handle_error/sub/__init__.py
new file mode 100644
index 0000000..abe851f
--- /dev/null
+++ b/importscan/tests/fixtures/importerror_pkg_handle_error/sub/__init__.py
@@ -0,0 +1 @@
+raise ImportError("cannot import sub")
diff --git a/importscan/tests/test_importscan.py b/importscan/tests/test_importscan.py
index 5db700a..61b55a4 100644
--- a/importscan/tests/test_importscan.py
+++ b/importscan/tests/test_importscan.py
@@ -5,10 +5,14 @@
 import re
 import sys
 from typing import TYPE_CHECKING
+from unittest.mock import MagicMock, patch
 
 import pytest
 from pytest import raises
+
 from importscan import scan
+from importscan.scan import import_module
+
 from . import fixtures
 
 if TYPE_CHECKING:
@@ -185,3 +189,85 @@ def test_module_in_zipped() -> None:
     scan(moduleinzipped)
 
     assert fixtures.calls == 1
+
+
+def test_scan_loader_file_close() -> None:
+    # __init__.py overwrites the 'scan' attribute with the function, so
+    # `import importscan.scan as x` resolves via getattr and yields the
+    # function; sys.modules gives the actual module object.
+    scan_mod = sys.modules["importscan.scan"]
+
+    from .fixtures import package
+
+    mock_file = MagicMock()
+    mock_loader = MagicMock()
+    mock_loader.file = mock_file
+    mock_spec = MagicMock()
+    mock_spec.loader = mock_loader
+    mock_importer = MagicMock()
+    mock_importer.find_spec.return_value = mock_spec
+
+    # patch.object avoids ambiguity from importscan.__init__ re-exporting scan
+    with patch.object(scan_mod, "walk_packages") as mock_wp:
+        mock_wp.return_value = iter(
+            [(mock_importer, "importscan.tests.fixtures.package.module", False)]
+        )
+        with patch.object(scan_mod, "import_module"):
+            scan(package)
+
+    mock_file.close.assert_called_once()
+
+
+class _LoaderUnderscoreGetFilename:
+    def _get_filename(self, modname: str | None = None) -> str:
+        return "some_module.py"
+
+
+class _LoaderGetFilenameTypeError:
+    def get_filename(self, modname: str | None = None) -> str:
+        if modname is not None:
+            raise TypeError
+        return "some_module.py"
+
+
+class _LoaderPycFilename:
+    def get_filename(self, modname: str | None = None) -> str:
+        return "some_module.pyc"
+
+
+def test_import_module_underscore_get_filename() -> None:
+    loader = _LoaderUnderscoreGetFilename()
+    with patch("builtins.__import__"):
+        import_module("somemodule", loader, None)  # type: ignore[arg-type]
+
+
+def test_import_module_get_filename_typeerror() -> None:
+    loader = _LoaderGetFilenameTypeError()
+    with patch("builtins.__import__"):
+        import_module("somemodule", loader, None)  # type: ignore[arg-type]
+
+
+def test_import_module_pyc_skipped() -> None:
+    loader = _LoaderPycFilename()
+    with patch("builtins.__import__") as mock_import:
+        import_module("somemodule", loader, None)  # type: ignore[arg-type]
+    mock_import.assert_not_called()
+
+
+def test_walk_packages_importerror_subpackage() -> None:
+    from .fixtures import importerror_pkg
+
+    with raises(ImportError):
+        scan(importerror_pkg)
+
+
+def test_walk_packages_importerror_subpackage_handle_error() -> None:
+    from .fixtures import importerror_pkg_handle_error
+
+    errors: list[str] = []
+
+    def handle_error(name: str, e: Exception) -> None:
+        errors.append(name)
+
+    scan(importerror_pkg_handle_error, handle_error=handle_error)
+    assert len(errors) == 1
diff --git a/pyproject.toml b/pyproject.toml
index acb45e6..da3a6a9 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -35,7 +35,7 @@ Changelog = "https://github.com/morepath/importscan/blob/master/CHANGES.txt"
 [project.optional-dependencies]
 test = ["pytest >= 8", "pytest-env"]
 coverage = ["pytest-cov"]
-lint = ["black", "flake8", "flake8-pyproject"]
+lint = ["black", "flake8", "flake8-pyproject", "isort"]
 docs = ["sphinx"]
 mypy = ["mypy", "pytest"]
 pyright = ["pyright", "pytest"]
@@ -71,15 +71,20 @@ max-line-length = 88
 python_version = "3.10"
 strict = true
 warn_unreachable = true
+warn_unused_ignores = true
 
 [[tool.mypy.overrides]]
 module = "importscan.tests.fixtures.*"
 ignore_errors = true
 
 [tool.pyright]
+typeCheckingMode = "strict"
+venvPath = "."
+venv = ".venv"
 exclude = [
-  "**/tests/fixtures/**",
+  "**/tests/fixtures/**", "**/__pycache__",
 ]
+reportUnnecessaryTypeIgnoreComment = "warning"
 
 [tool.tox]
 requires = ["tox>=4"]
@@ -154,3 +159,29 @@ commands = [
     ["pyright", "importscan", "--pythonversion", "3.13"],
     ["pyright", "importscan", "--pythonversion", "3.14"],
 ]
+
+[tool.black]
+target-version = ['py310', 'py311', 'py312', 'py313', 'py314']
+include = '\.pyi?$'
+exclude = '''
+(
+  /(
+      \.git
+    | \.tox
+    | env
+    | venv
+    | .venv
+    | __pycache__
+    | build
+    | dist
+    | src
+  )/
+)
+'''
+
+[tool.isort]
+profile = 'black'
+py_version = 310
+skip_gitignore = true
+extra_standard_library = ["typing_extensions"]
+known_first_party = ["dectate", "importscan", "reg"]