Fix crash when users run Nox with the new --no-install option (#382)

* build: Add typing_extensions ^3.10.0 to dev dependencies

* ci: Install typing_extensions in tests session

* test: Allow functional tests to pass command-line arguments to Nox

* test: Add functional tests for --no-install

* test: Add fixture sessionfactory for simulating --no-install

* test: Add unit tests for --no-install

* feat: Raise CommandSkippedError if Nox skipped `poetry` command

* feat: Return early if `poetry` command raises CommandSkippedError

noxfile.py

@@ -126,6 +126,7 @@ def tests(session: Session, poetry: Optional[str]) -> None:
         "pytest",
         "pytest-datadir",
         "pygments",
+        "typing_extensions",
     )
     if session.python == "3.6":
         session.install("dataclasses")

pyproject.toml

@@ -50,6 +50,7 @@ Pygments = "^2.9.0"
 poetry = "^1.1.6"
 pytest-datadir = "^1.3.1"
 dataclasses = {version = "^0.8", python = "<3.7"}
+typing-extensions = "^3.10.0"
 
 [tool.coverage.paths]
 source = ["src", "*/site-packages"]

src/nox_poetry/poetry.py

@@ -9,6 +9,10 @@
 from nox.sessions import Session
 
 
+class CommandSkippedError(Exception):
+    """The command was not executed by Nox."""
+
+
 class DistributionFormat(str, Enum):
     """Type of distribution archive for a Python package."""
 
@@ -67,6 +71,9 @@ def export(self) -> str:
 
         Returns:
             The generated requirements as text.
+
+        Raises:
+            CommandSkippedError: The command `poetry export` was not executed.
         """
         output = self.session.run_always(
             "poetry",
@@ -79,6 +86,13 @@ def export(self) -> str:
             silent=True,
             stderr=None,
         )
+
+        if output is None:
+            raise CommandSkippedError(
+                "The command `poetry export` was not executed"
+                " (a possible cause is specifying `--no-install`)"
+            )
+
         assert isinstance(output, str)  # noqa: S101
         return output
 
@@ -102,6 +116,9 @@ def build(self, *, format: str) -> str:
 
         Returns:
             The basename of the wheel built by Poetry.
+
+        Raises:
+            CommandSkippedError: The command `poetry build` was not executed.
         """
         if not isinstance(format, DistributionFormat):
             format = DistributionFormat(format)
@@ -114,5 +131,12 @@ def build(self, *, format: str) -> str:
             silent=True,
             stderr=None,
         )
+
+        if output is None:
+            raise CommandSkippedError(
+                "The command `poetry build` was not executed"
+                " (a possible cause is specifying `--no-install`)"
+            )
+
         assert isinstance(output, str)  # noqa: S101
         return output.split()[-1]

src/nox_poetry/sessions.py

@@ -13,6 +13,7 @@
 from packaging.requirements import InvalidRequirement
 from packaging.requirements import Requirement
 
+from nox_poetry.poetry import CommandSkippedError
 from nox_poetry.poetry import DistributionFormat
 from nox_poetry.poetry import Poetry
 
@@ -125,7 +126,10 @@ def install(self, *args: str, **kwargs: Any) -> None:
         args_extras = [_split_extras(arg) for arg in args]
 
         if "." in [arg for arg, _ in args_extras]:
-            package = self.build_package()
+            try:
+                package = self.build_package()
+            except CommandSkippedError:
+                return
 
             def rewrite(arg: str, extras: Optional[str]) -> str:
                 if arg != ".":
@@ -141,7 +145,11 @@ def rewrite(arg: str, extras: Optional[str]) -> str:
 
             self.session.run_always("pip", "uninstall", "--yes", package, silent=True)
 
-        requirements = self.export_requirements()
+        try:
+            requirements = self.export_requirements()
+        except CommandSkippedError:
+            return
+
         Session_install(self.session, f"--constraint={requirements}", *args, **kwargs)
 
     def installroot(
@@ -167,8 +175,11 @@ def installroot(
         """
         from nox_poetry.core import Session_install
 
-        package = self.build_package(distribution_format=distribution_format)
-        requirements = self.export_requirements()
+        try:
+            package = self.build_package(distribution_format=distribution_format)
+            requirements = self.export_requirements()
+        except CommandSkippedError:
+            return
 
         self.session.run_always("pip", "uninstall", "--yes", package, silent=True)
 

tests/functional/conftest.py

@@ -90,13 +90,13 @@ def project(datadir: Path) -> Project:
     return Project(datadir / "example")
 
 
-def _run_nox(project: Project) -> CompletedProcess:
+def _run_nox(project: Project, *nox_args: str) -> CompletedProcess:
     env = os.environ.copy()
     env.pop("NOXSESSION", None)
 
     try:
         return subprocess.run(  # noqa: S603, S607
-            ["nox"],
+            ["nox", *nox_args],
             check=True,
             universal_newlines=True,
             stdout=subprocess.PIPE,
@@ -128,10 +128,11 @@ def run_nox_with_noxfile(
     project: Project,
     sessions: Iterable[SessionFunction],
     imports: Iterable[ModuleType],
+    *nox_args: str,
 ) -> None:
     """Write a noxfile and run Nox in the project."""
     _write_noxfile(project, sessions, imports)
-    _run_nox(project)
+    _run_nox(project, *nox_args)
 
 
 def list_packages(project: Project, session: SessionFunction) -> List[Package]:

tests/functional/test_functional.py

@@ -359,3 +359,37 @@ def test(session: nox_poetry.Session) -> None:
         session.poetry.export_requirements()
 
     run_nox_with_noxfile(project, [test], [nox_poetry])
+
+
+def test_install_no_install(project: Project) -> None:
+    """It skips installation when --no-install is passed."""
+
+    @nox_poetry.session
+    def test(session: nox_poetry.Session) -> None:
+        """Install the local package."""
+        session.install(".")
+
+    run_nox_with_noxfile(project, [test], [nox_poetry])
+    run_nox_with_noxfile(project, [test], [nox_poetry], "-R")
+
+    expected = [project.package, *project.dependencies]
+    packages = list_packages(project, test)
+
+    assert set(expected) == set(packages)
+
+
+def test_installroot_no_install(project: Project) -> None:
+    """It skips installation when --no-install is passed."""
+
+    @nox_poetry.session
+    def test(session: nox_poetry.Session) -> None:
+        """Install the local package."""
+        session.poetry.installroot()
+
+    run_nox_with_noxfile(project, [test], [nox_poetry])
+    run_nox_with_noxfile(project, [test], [nox_poetry], "-R")
+
+    expected = [project.package, *project.dependencies]
+    packages = list_packages(project, test)
+
+    assert set(expected) == set(packages)

tests/unit/conftest.py

@@ -1,7 +1,14 @@
 """Fixtures."""
+import sys
 from pathlib import Path
 from typing import Any
 from typing import cast
+from typing import Optional
+
+if sys.version_info >= (3, 8):
+    from typing import Protocol
+else:
+    from typing_extensions import Protocol
 
 import pytest
 from _pytest.monkeypatch import MonkeyPatch
@@ -19,23 +26,46 @@ def __init__(self, path: Path) -> None:
 class FakeSession:
     """Fake session."""
 
-    def __init__(self, path: Path) -> None:
+    def __init__(self, path: Path, no_install: bool) -> None:
         """Initialize."""
         self._runner = FakeSessionRunner(path)
+        self.no_install = no_install
+        self.install_called = False
 
-    def run_always(self, *args: str, **kargs: Any) -> str:
+    def run_always(self, *args: str, **kargs: Any) -> Optional[str]:
         """Run."""
+        if self.no_install:
+            return None
+
         path = Path("dist") / "example.whl"
         path.touch()
         return path.name
 
     def install(self, *args: str, **kargs: Any) -> None:
         """Install."""
+        self.install_called = True
+
+
+class FakeSessionFactory(Protocol):
+    """Factory for fake sessions."""
+
+    def __call__(self, *, no_install: bool) -> Session:
+        """Create a fake session."""
+
+
+@pytest.fixture
+def sessionfactory(tmp_path: Path, monkeypatch: MonkeyPatch) -> FakeSessionFactory:
+    """Return a factory for a fake Nox session."""
+
+    def _sessionfactory(*, no_install: bool) -> Session:
+        monkeypatch.setattr("nox_poetry.core.Session_install", FakeSession.install)
+        session = FakeSession(tmp_path, no_install=no_install)
+        return cast(Session, session)
+
+    return _sessionfactory
 
 
 @pytest.fixture
-def session(tmp_path: Path, monkeypatch: MonkeyPatch) -> Session:
+def session(sessionfactory: FakeSessionFactory) -> Session:
     """Return a fake Nox session."""
-    monkeypatch.setattr("nox_poetry.core.Session_install", FakeSession.install)
-    session = FakeSession(tmp_path)
-    return cast(Session, session)
+    return sessionfactory(no_install=False)

tests/unit/test_sessions.py

@@ -1,12 +1,15 @@
 """Unit tests for the sessions module."""
 from textwrap import dedent
 from typing import Callable
+from typing import cast
 from typing import Iterator
 
 import nox._options
 import nox.manifest
 import nox.registry
 import pytest
+from tests.unit.conftest import FakeSession
+from tests.unit.conftest import FakeSessionFactory
 
 import nox_poetry
 from nox_poetry.sessions import to_constraints  # type: ignore[attr-defined]
@@ -175,3 +178,42 @@ def test_invalid_constraint() -> None:
     """It raises an exception."""
     with pytest.raises(Exception):
         to_constraints("example @ /tmp/example")
+
+
+@pytest.mark.parametrize("no_install", [False, True])
+def test_install_local_no_install(
+    sessionfactory: FakeSessionFactory, no_install: bool
+) -> None:
+    """It returns early with --no-install if the environment is being reused."""
+    session = sessionfactory(no_install=no_install)
+    proxy = nox_poetry.Session(session)
+
+    proxy.install(".")
+
+    assert cast(FakeSession, session).install_called is not no_install
+
+
+@pytest.mark.parametrize("no_install", [False, True])
+def test_install_dependency_no_install(
+    sessionfactory: FakeSessionFactory, no_install: bool
+) -> None:
+    """It returns early with --no-install if the environment is being reused."""
+    session = sessionfactory(no_install=no_install)
+    proxy = nox_poetry.Session(session)
+
+    proxy.install("first")
+
+    assert cast(FakeSession, session).install_called is not no_install
+
+
+@pytest.mark.parametrize("no_install", [False, True])
+def test_installroot_no_install(
+    sessionfactory: FakeSessionFactory, no_install: bool
+) -> None:
+    """It returns early with --no-install if the environment is being reused."""
+    session = sessionfactory(no_install=no_install)
+    proxy = nox_poetry.Session(session)
+
+    proxy.poetry.installroot()
+
+    assert cast(FakeSession, session).install_called is not no_install