fix(strict-deps): fail if venv is inconsistent

This runs `pip check` to ensure that all the packages in the charm
virtualenv have all of their required dependencies, failing the build
if they do not.

Fixes #1781

charmcraft/charm_builder.py

@@ -1,4 +1,4 @@
-# Copyright 2020-2023 Canonical Ltd.
+# Copyright 2020-2024 Canonical Ltd.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -61,18 +61,18 @@ def __init__(
         installdir: pathlib.Path,
         entrypoint: pathlib.Path,
         allow_pip_binary: bool = None,
-        binary_python_packages: list[str] = None,
-        python_packages: list[str] = None,
-        requirements: list[pathlib.Path] = None,
+        binary_python_packages: list[str] | None = None,
+        python_packages: list[str] | None = None,
+        requirements: list[pathlib.Path] | None = None,
         strict_dependencies: bool = False,
     ) -> None:
         self.builddir = builddir
         self.installdir = installdir
         self.entrypoint = entrypoint
         self.allow_pip_binary = allow_pip_binary
-        self.binary_python_packages = binary_python_packages
-        self.python_packages = python_packages
-        self.requirement_paths = requirements
+        self.binary_python_packages = binary_python_packages or []
+        self.python_packages = python_packages or []
+        self.requirement_paths = requirements or []
         self.strict_dependencies = strict_dependencies
         self.ignore_rules = self._load_juju_ignore()
         self.ignore_rules.extend_patterns([f"/{const.STAGING_VENV_DIRNAME}"])
@@ -227,7 +227,7 @@ def _calculate_dependencies_hash(self):
         return hashlib.sha1(deps_mashup.encode("utf8")).hexdigest()
 
     @instrum.Timer("Installing dependencies")
-    def _install_dependencies(self, staging_venv_dir):
+    def _install_dependencies(self, staging_venv_dir: pathlib.Path):
         """Install all dependencies in a specific directory."""
         # create virtualenv using the host environment python
         with instrum.Timer("Creating venv"):
@@ -309,6 +309,8 @@ def _install_strict_dependencies(self, pip_cmd: str) -> None:
                 binary_deps=self.binary_python_packages or [],
             )
         )
+        # Validate that the environment is consistent.
+        _process_run([pip_cmd, "check"])
 
     def handle_dependencies(self):
         """Handle from-directory and virtualenv dependencies."""

tests/unit/test_charm_builder.py

@@ -1,4 +1,4 @@
-# Copyright 2023 Canonical Ltd.
+# Copyright 2023-2024 Canonical Ltd.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -105,6 +105,10 @@ def test_install_strict_dependencies_success(
         "--no-binary=:all:",
         "--requirement=requirements.txt",
     ]
-    fake_process.register(expected_command, returncode=0)
+    install_cmd = fake_process.register(expected_command, returncode=0)
+    check_cmd = fake_process.register(["/pip", "check"], returncode=0)
 
     builder._install_strict_dependencies("/pip")
+
+    assert install_cmd.call_count() == 1
+    assert check_cmd.call_count() == 1