233 strict typing (#238)

Fixes #233

Author: callumforrester

copier.yml

@@ -122,6 +122,18 @@ type_checker:
         - pyright
         - mypy
 
+strict_typing:
+    type: bool
+    when: >-
+        {{ type_checker == 'pyright' }}
+    default: true
+    help: |
+        Would you like to run pyright in strict mode?
+        The recommended approach is to start with strict mode and disable it if it 
+        becomes too costly to maintain. 
+        See https://diamondlightsource.github.io/python-copier-template/main/how-to/strict-mode.html 
+        for more information.
+
 pypi:
     type: bool
     help: Would you like the wheel and source distribution to be automatically uploaded to PyPI when a release is made?

docs/how-to/strict-mode.md

@@ -1,17 +1,13 @@
-# Enable Pyright's Strict Mode
+# Use Pyright's Strict Mode
 
-For projects using pyright you can enable strict mode for stricter than normal type checking. See [the docs](https://github.com/microsoft/pyright/blob/main/docs/configuration.md) for a full breakdown. The primary benefits are increased confidence in code that has been more thoroughly analyzed and a shorter development time thanks to fast feedback from the type checker.
+For projects using pyright you can enable strict mode for stricter than normal type checking. See [the docs](https://github.com/microsoft/pyright/blob/main/docs/configuration.md) for a full breakdown. 
 
-## Configuration
+## How to Enable
 
-Change the `typeCheckingMode` line to `"strict"` in `pyproject.toml` as follows:
+When creating a template, select `pyright` as the type checker and type `y` when prompted to enable strict mode.
 
-```toml
-[tool.pyright]
-typeCheckingMode = "strict"
-reportMissingImports = false # Ignore missing stubs in imported modules
-```
+## Who Should Use Strict Mode?
 
-## Third Party Libraries
+Strict mode enforces good practices such as type hints on function signatures, providing increased confidence in code that has been more thoroughly analyzed and a shorter development time thanks to fast feedback from the type checker. Starting a new project and continually keeping it passing provides a long-term benefit when it comes to maintanability and robustness. However, adopting strict mode on top of legacy projects is likely to lead to lots of errors to work through - probably thousands. Additionally it does not usually work well with libraries that do not have [type stubs](https://github.com/microsoft/pyright/blob/main/docs/type-stubs.md), you will likely need a `# type: ignore` on any line that directly uses the library code. This may limit the usefulness of pyright but it can still be worth doing to ensure your own code is internally consistent.
 
-Strict mode does not usually work well with libraries that do not have [type stubs](https://github.com/microsoft/pyright/blob/main/docs/type-stubs.md), you will likely need a `# type: ignore` on any line that directly uses the library code. This may limit the usefulness of pyright but it can still be worth doing to ensure your own code is internally consistent.
+The recommended approach for brand new projects is to enable strict mode and stick with it for as long as is practical, moving away if it starts to cause more hindrance than help (e.g. because too many major dependencies do not support it).

example-answers.yml

@@ -12,4 +12,5 @@ github_org: DiamondLightSource
 package_name: python_copier_template_example
 repo_name: python-copier-template-example
 type_checker: pyright
+strict_typing: true
 pypi: true

template/pyproject.toml.jinja

@@ -51,9 +51,11 @@ name = "{{ author_name }}"
 [tool.setuptools_scm]
 version_file = "src/{{ package_name }}/_version.py"
 {% if type_checker=="pyright" %}
-[tool.pyright]
+[tool.pyright]{% if strict_typing %}
+typeCheckingMode = "strict"
+{% else %}
 typeCheckingMode = "standard"
-reportMissingImports = false # Ignore missing stubs in imported modules
+{% endif %}reportMissingImports = false # Ignore missing stubs in imported modules
 {% endif %}{% if type_checker=="mypy" %}
 [tool.mypy]
 ignore_missing_imports = true # Ignore missing stubs in imported modules

tests/test_example.py

@@ -48,9 +48,11 @@ def test_template_defaults(tmp_path: Path):
     copy_project(tmp_path)
     run = make_venv(tmp_path)
     container_doc = tmp_path / "docs" / "how-to" / "run-container.md"
+    pyproject_toml = tmp_path / "pyproject.toml"
     assert container_doc.exists()
     catalog_info = tmp_path / "catalog-info.yaml"
     assert catalog_info.exists()
+    assert 'typeCheckingMode = "strict"' in pyproject_toml.read_text()
     run("./venv/bin/tox -p")
     if not run_pipe("git tag --points-at HEAD"):
         # Only run linkcheck if not on a tag, as the CI might not have pushed
@@ -68,8 +70,16 @@ def test_template_with_extra_code_and_api_docs(tmp_path: Path):
     init = tmp_path / "src" / "python_copier_template_example" / "__init__.py"
     init.write_text(
         init.read_text().replace(
-            "__all__ = [",
+            """
+from ._version import __version__
+
+__all__ = [""",
             '''
+from python_copier_template_example import extra_pkg
+
+from ._version import __version__
+
+
 class TopCls:
     """A top level class."""
 
@@ -213,21 +223,26 @@ def __init__(self):
         run("ruff check")
 
 
-def test_works_in_pyright_strict_mode(tmp_path: Path):
-    copy_project(tmp_path)
+def test_pyright_works_in_standard_typing_mode(tmp_path: Path):
+    copy_project(tmp_path, type_checker="pyright", strict_typing=False)
     pyproject_toml = tmp_path / "pyproject.toml"
 
-    # Enable strict mode
-    run_pipe(
-        'sed -i \'s|typeCheckingMode = "standard"|typeCheckingMode = "strict"|\''
-        f" {pyproject_toml}"
-    )
+    # Check standard mode is configured
+    assert 'typeCheckingMode = "standard"' in pyproject_toml.read_text()
 
     # Ensure pyright is still happy
     run = make_venv(tmp_path)
     run(f"./venv/bin/pyright {tmp_path}")
 
 
+def test_ignores_mypy_strict_mode(tmp_path: Path):
+    copy_project(tmp_path, type_checker="mypy", strict_typing=True)
+    pyproject_toml = tmp_path / "pyproject.toml"
+
+    # Check strict mode is not configured
+    assert "typeCheckingMode =" not in pyproject_toml.read_text()
+
+
 def test_works_with_pydocstyle(tmp_path: Path):
     copy_project(tmp_path)
     pyproject_toml = tmp_path / "pyproject.toml"