Add function to monkey-patch Session.install (#108)

* Forward keyword arguments to Session.install

* Add nox_poetry.patch()

* Rename build_package parameter {format => distribution_format}

* Ignore RST201 "Block quote ends without a blank line"

* Use nox_poetry.patch() in noxfile.py

* Rename local variable {format => distribution_format}

* Monkey-patch core.Session_install in tests

* Simplify imports in tests

* Add test case for nox_poetry.patch

* Update README.rst

.flake8

@@ -1,6 +1,6 @@
 [flake8]
 select = B,B9,C,D,DAR,E,F,N,RST,S,W
-ignore = E203,E501,RST203,RST301,W503
+ignore = E203,E501,RST201,RST203,RST301,W503
 max-line-length = 80
 max-complexity = 10
 docstring-convention = google

README.rst

@@ -33,13 +33,19 @@ nox-poetry
    :alt: Black
 
 
-Helper functions for using Poetry_ inside Nox_ sessions
+Use Poetry_ inside Nox_ sessions
+
+This package provides a drop-in replacement for ``session.install`` in Nox sessions.
+It modifies its behavior in two ways:
+
+- Packages are pinned to the versions specified in Poetry's lock file.
+- The argument ``"."`` is replaced by a wheel built from the package.
 
 
 Installation
 ------------
 
-You can install ``nox-poetry`` via pip_ from the Python Package Index:
+Install ``nox-poetry`` from the Python Package Index:
 
 .. code:: console
 
@@ -59,23 +65,32 @@ use the following command to install this package into the same environment:
 Usage
 -----
 
-- The function ``nox_poetry.install(session, ...)`` is a drop-in replacement for ``session.install(...)``.
-- Packages installed like this must be declared as dependencies using Poetry.
-- Use the constants ``WHEEL`` and ``SDIST`` to build and install your own package.
+Invoke ``nox_poetry.patch()`` at the top of your ``noxfile.py``, and you're good to go.
+``nox-poetry`` intercepts calls to ``session.install``
+and uses Poetry to export a `constraints file`_ and build the package behind the scenes.
+
+If you prefer a less magical, more explicit approach,
+you can also invoke ``nox_poetry.install(session, ...)`` instead of ``session.install(...)``.
+Pass ``nox_poetry.WHEEL`` or ``nox_poetry.SDIST`` to build and install the local package
+using the specified distribution format.
+
+Packages installed in this way must be managed as dependencies in Poetry.
 
 For example, the following Nox session runs your test suite:
 
 .. code:: python
 
    # noxfile.py
    import nox
-   from nox.sessions import Session
-   from nox_poetry import install, WHEEL
+   import nox_poetry
+
+   nox_poetry.patch()
 
    @nox.session
    def tests(session: Session) -> None:
        """Run the test suite."""
-       install(session, WHEEL, "pytest")
+       session.install(".")
+       session.install("pytest")
        session.run("pytest")
 
 More precisely, the session builds a wheel from the local package,
@@ -86,24 +101,16 @@ invokes ``pytest`` to run the test suite against the installation.
 Why?
 ----
 
-Compare the session above to one written without this package:
+Consider what would happen in the above session with an unpatched ``session.install``:
 
-.. code:: python
-
-   @nox.session
-   def tests(session: Session) -> None:
-       """Run the test suite."""
-       session.install(".")
-       session.install("pytest")
-       session.run("pytest")
-
-This session has several problems:
-
-- Poetry is installed as a build backend every time.
-- Package dependencies are only constrained by the wheel metadata, not by the lock file.
-  In other words, their versions are not *pinned*.
-- The ``pytest`` dependency is not constrained at all.
+- Package dependencies would only be constrained by the wheel metadata, not by the lock file.
+  In other words, their versions would not be *pinned*.
+- The ``pytest`` dependency would not be constrained at all.
+- Poetry would be installed as a build backend every time
+  (although this could be avoided by passing the ``"--no-build-isolation"`` option).
 
+Unpinned dependencies mean that your checks are not reproducible and deterministic,
+which can lead to surprises in Continuous Integration and when collaborating with others.
 You can solve these issues by declaring ``pytest`` as a development dependency,
 and installing your package and its dependencies using ``poetry install``:
 
@@ -115,7 +122,7 @@ and installing your package and its dependencies using ``poetry install``:
        session.run("poetry", "install", external=True)
        session.run("pytest")
 
-Unfortunately, this approach creates problems of its own:
+Unfortunately, this approach comes with its own set of problems:
 
 - Checks run against an editable installation of your package,
   i.e. your local copy of the code, instead of the installed wheel your users see.
@@ -128,9 +135,10 @@ Unfortunately, this approach creates problems of its own:
 Third-party packages are installed by exporting the lock file in ``requirements.txt`` format,
 and passing it as a `constraints file`_ to pip.
 When installing your own package, Poetry is used to build a wheel, which is then installed by pip.
-This approach has some advantages:
 
-- You can declare tools like ``pytest`` as development dependencies in Poetry.
+In summary, this approach brings the following advantages:
+
+- You can manage tools like ``pytest`` as development dependencies in Poetry.
 - Dependencies are pinned by Poetry's lock file, making checks predictable and deterministic.
 - You can run checks against an installed wheel, instead of your local copy of the code.
 - Every tool can run in an isolated environment with minimal dependencies.
@@ -144,7 +152,14 @@ __ https://cjolowicz.github.io/posts/hypermodern-python-03-linting/#managing-dep
 API
 ---
 
-``nox_poetry.install(session, *args)``:
+``nox_poetry.patch(*, distribution_format=nox_poetry.WHEEL)``:
+   Monkey-patch `nox.sessions.Session.install`_ to use ``nox_poetry.install``.
+   The optional ``distribution_format`` parameter determines
+   how to handle the special ``"."`` argument.
+   By default, this is replaced by a wheel built from the package.
+   Pass ``nox_poetry.SDIST`` to build an sdist archive instead.
+
+``nox_poetry.install(session, *args, **kwargs)``:
    Install packages into a Nox session using Poetry.
 
    The ``nox_poetry.install`` function
@@ -156,6 +171,7 @@ API
    typically just the package or packages to be installed.
    The constants ``WHEEL`` and ``SDIST`` are replaced by a distribution archive
    built for the local package.
+   Keyword arguments are the same as those for `nox.sessions.Session.run`_.
 
 
 Contributing

noxfile.py

@@ -7,9 +7,10 @@
 import nox
 from nox.sessions import Session
 
-from nox_poetry import export_requirements
-from nox_poetry import install
-from nox_poetry import WHEEL
+import nox_poetry
+
+
+nox_poetry.patch()
 
 
 package = "nox_poetry"
@@ -78,8 +79,7 @@ def activate_virtualenv_in_precommit_hooks(session: Session) -> None:
 def precommit(session: Session) -> None:
     """Lint using pre-commit."""
     args = session.posargs or ["run", "--all-files", "--show-diff-on-failure"]
-    install(
-        session,
+    session.install(
         "black",
         "darglint",
         "flake8",
@@ -100,16 +100,16 @@ def precommit(session: Session) -> None:
 @nox.session(python="3.8")
 def safety(session: Session) -> None:
     """Scan dependencies for insecure packages."""
-    install(session, "safety")
-    requirements = export_requirements(session)
+    session.install("safety")
+    requirements = nox_poetry.export_requirements(session)
     session.run("safety", "check", f"--file={requirements}", "--bare")
 
 
 @nox.session(python=python_versions)
 def mypy(session: Session) -> None:
     """Type-check using mypy."""
     args = session.posargs or ["src", "tests", "docs/conf.py"]
-    install(session, WHEEL, "mypy")
+    session.install(".", "mypy")
     session.run("mypy", *args)
     if not session.posargs:
         session.run("mypy", f"--python-executable={sys.executable}", "noxfile.py")
@@ -118,7 +118,7 @@ def mypy(session: Session) -> None:
 @nox.session(python=python_versions)
 def tests(session: Session) -> None:
     """Run the test suite."""
-    install(session, WHEEL, "coverage[toml]", "pytest")
+    session.install(".", "coverage[toml]", "pytest")
     try:
         session.run("coverage", "run", "--parallel", "-m", "pytest", *session.posargs)
     finally:
@@ -132,7 +132,7 @@ def coverage(session: Session) -> None:
     has_args = session.posargs and len(session._runner.manifest) == 1
     args = session.posargs if has_args else ["report"]
 
-    install(session, "coverage[toml]")
+    session.install("coverage[toml]")
 
     if not has_args and any(Path().glob(".coverage.*")):
         session.run("coverage", "combine")
@@ -143,23 +143,23 @@ def coverage(session: Session) -> None:
 @nox.session(python=python_versions)
 def typeguard(session: Session) -> None:
     """Runtime type checking using Typeguard."""
-    install(session, WHEEL, "pytest", "typeguard")
+    session.install(".", "pytest", "typeguard")
     session.run("pytest", f"--typeguard-packages={package}", *session.posargs)
 
 
 @nox.session(python=python_versions)
 def xdoctest(session: Session) -> None:
     """Run examples with xdoctest."""
     args = session.posargs or ["all"]
-    install(session, WHEEL, "xdoctest")
+    session.install(".", "xdoctest")
     session.run("python", "-m", "xdoctest", package, *args)
 
 
 @nox.session(name="docs-build", python="3.8")
 def docs_build(session: Session) -> None:
     """Build the documentation."""
     args = session.posargs or ["docs", "docs/_build"]
-    install(session, WHEEL, "sphinx")
+    session.install(".", "sphinx")
 
     build_dir = Path("docs", "_build")
     if build_dir.exists():
@@ -172,7 +172,7 @@ def docs_build(session: Session) -> None:
 def docs(session: Session) -> None:
     """Build and serve the documentation with live reloading on file changes."""
     args = session.posargs or ["--open-browser", "docs", "docs/_build"]
-    install(session, WHEEL, "sphinx", "sphinx-autobuild")
+    session.install(".", "sphinx", "sphinx-autobuild")
 
     build_dir = Path("docs", "_build")
     if build_dir.exists():

src/nox_poetry/__init__.py

@@ -1,6 +1,7 @@
 """Using Poetry in Nox sessions."""
 from nox_poetry.core import export_requirements
 from nox_poetry.core import install
+from nox_poetry.core import patch
 from nox_poetry.poetry import DistributionFormat
 
 
@@ -10,6 +11,7 @@
 __all__ = [
     "export_requirements",
     "install",
-    "WHEEL",
+    "patch",
     "SDIST",
+    "WHEEL",
 ]

src/nox_poetry/core.py

@@ -1,6 +1,8 @@
 """Core functions."""
 import hashlib
 from pathlib import Path
+from typing import Any
+from typing import List
 from typing import Union
 
 from nox.sessions import Session
@@ -9,6 +11,9 @@
 from nox_poetry.poetry import Poetry
 
 
+Session_install = Session.install
+
+
 def export_requirements(session: Session) -> Path:
     """Export the lock file to requirements format.
 
@@ -32,29 +37,31 @@ def export_requirements(session: Session) -> Path:
     return path
 
 
-def build_package(session: Session, *, format: DistributionFormat) -> str:
+def build_package(session: Session, *, distribution_format: DistributionFormat) -> str:
     """Build a distribution archive for the package.
 
     Args:
         session: The Session object.
-        format: The distribution format, either wheel or sdist.
+        distribution_format: The distribution format, either wheel or sdist.
 
     Returns:
         The file URL for the distribution package.
     """
     # Provide a hash for the wheel since the constraints file uses hashes.
     # https://pip.pypa.io/en/stable/reference/pip_install/#hash-checking-mode
     poetry = Poetry(session)
-    wheel = Path("dist") / poetry.build(format=format)
+    wheel = Path("dist") / poetry.build(format=distribution_format)
     digest = hashlib.sha256(wheel.read_bytes()).hexdigest()
 
     return f"file://{wheel.resolve().as_posix()}#sha256={digest}"
 
 
-def install(session: Session, *args: Union[DistributionFormat, str]) -> None:
+def install(
+    session: Session, *args: Union[DistributionFormat, str], **kwargs: Any
+) -> None:
     """Install packages into the session's virtual environment.
 
-    This function is a wrapper for nox.sessions.Session.install.
+    This function is a wrapper for ``nox.sessions.Session.install``.
 
     The packages must be managed as dependencies in Poetry.
 
@@ -63,20 +70,37 @@ def install(session: Session, *args: Union[DistributionFormat, str]) -> None:
         args: Command-line arguments for ``pip install``. The ``WHEEL``
             and ``SDIST`` constants are replaced by a wheel or sdist
             archive built from the local package.
+        kwargs: Keyword-arguments for ``session.install``.
     """
     resolved = {
         arg: (
-            build_package(session, format=arg)
+            build_package(session, distribution_format=arg)
             if isinstance(arg, DistributionFormat)
             else arg
         )
         for arg in args
     }
 
-    for format in DistributionFormat:
-        package = resolved.get(format)
+    for distribution_format in DistributionFormat:
+        package = resolved.get(distribution_format)
         if package is not None:
             session.run("pip", "uninstall", "--yes", package, silent=True)
 
     requirements = export_requirements(session)
-    session.install(f"--constraint={requirements}", *resolved.values())
+    Session_install(
+        session, f"--constraint={requirements}", *resolved.values(), **kwargs
+    )
+
+
+def patch(
+    *, distribution_format: DistributionFormat = DistributionFormat.WHEEL
+) -> None:
+    """Monkey-patch nox.sessions.Session.install with nox_poetry.install."""
+
+    def patched_install(self: Session, *args: str, **kwargs: Any) -> None:
+        newargs: List[Union[DistributionFormat, str]] = [
+            distribution_format if arg == "." else arg for arg in args
+        ]
+        install(self, *newargs, **kwargs)
+
+    Session.install = patched_install  # type: ignore[assignment]