Check for pip configuration when an externally managed environment is detected.

doc/contents.rst

@@ -11,3 +11,4 @@ Contents
    sources_list
    developers_guide
    rosdep2_api
+   pip_and_pep_668

doc/pip_and_pep_668.rst

@@ -0,0 +1,72 @@
+Pip installation after PEP 668
+==============================
+
+`PEP-668`_ introduced `externally managed environments <externally-managed-environments>`_ to Python packaging.
+
+``rosdep`` is designed to use pip as an alternative system package manager, rosdep installation of pip packages requires installing packages globally as root.
+Starting with Python 3.11, `PEP-668`_ compliance requires you to allow pip to install alongside externally managed packages using the ``break-system-packages`` option.
+
+There are multiple ways to configure pip so that rosdep will succeed.
+
+
+Configure using environment variable
+------------------------------------
+
+This is the way that we recommend configuring pip for rosdep usage.
+We recommend configuring pip using the system environment.
+Setting environment variables in your login profile, ``PIP_BREAK_SYSTEM_PACKAGES`` in your environment.
+The value of the environment variable can be any of ``1``, ``yes``, or ``true``.
+The string values are not case sensitive.
+
+``rosdep`` is designed to use ``sudo`` in order to gain root privileges for installation when not run as root.
+If your system's sudo configuration prohibits the passing of environment variables
+
+
+Configure using pip.conf
+------------------------
+
+`Pip configuration files <pip-configuration>`_ can be used to set the desired behavior 
+Pip checks for global configuration files in ``XDG_CONFIG_DIRS``, as well as ``/etc/pip.conf``
+For details on ``XDG_CONFIG_DIRS`` refer to the `XDG base directories specification <xdg-base-dirs>`_.
+If you're unsure which configuration file is in use by your system, ``/etc/pip.conf`` seems like the most generic.
+
+.. code-block:: ini
+
+   [install]
+   break-system-packages = true
+
+
+.. warning:: Creating a pip.conf in your user account's ``XDG_CONFIG_HOME`` (e.g. ``~/.config/pip/pip.conf``) does not appear to be sufficent when installing packages globally.
+
+
+Configuring for CI setup
+------------------------
+
+Either environment variables or configuration files can be used with your CI system.
+Which one you choose will depend on how your CI environment is configured.
+Perhaps the most straightforward will be to set the environent variable in the shell or script execution context before invoking rosdep.
+
+.. code-block:: bash
+
+   sudo rosdep init
+   rosdep update
+   PIP_BREAK_SYSTEM_PACKAGES=1 rosdep install -r rolling --from-paths src/
+
+If rosdep is invoked by internal processes in your CI and you need to set the configuration without having direct control over how ``rosdep install`` is run, setting the environment variable globally would also work.
+
+.. code-block:: bash
+
+   export PIP_BREAK_SYSTEM_PACKAGES=1
+   ./path/to/ci-script.sh
+
+
+If you cannot set environment variables but you can create configuration files, you can set ``/etc/pip.conf`` with the necessary configuration.
+
+.. code-block:: bash
+
+   printf "[install]\nbreak-system-packages = true\n" | sudo tee -a /etc/pip.conf
+
+.. _PEP-668: https://peps.python.org/pep-0668/
+.. _pip-configuration: https://pip.pypa.io/en/stable/topics/configuration/
+.. _externally-managed-environments: https://packaging.python.org/en/latest/specifications/externally-managed-environments/
+.. _xdg-base-dirs: https://specifications.freedesktop.org/basedir-spec/latest/

src/rosdep2/platforms/pip.py

@@ -31,6 +31,9 @@
 import subprocess
 import sys
 
+from configparser import ConfigParser
+from pathlib import Path
+
 try:
     import importlib.metadata as importlib_metadata
 except ImportError:
@@ -43,6 +46,17 @@
 # pip package manager key
 PIP_INSTALLER = 'pip'
 
+EXTERNALLY_MANAGED_EXPLAINER = """
+rosdep installation of pip packages requires installing packages globally as root.
+When using Python >= 3.11, PEP 668 compliance requires you to allow pip to install alongside
+externally managed packages using the 'break-system-packages' option.
+The recommeded way to set this option when using rosdep is to set the environment variable
+PIP_BREAK_SYSTEM_PACKAGES=1
+in your environment.
+
+For more information refer to http://docs.ros.org/en/independent/api/rosdep/html/pip_and_pep_668.html
+"""
+
 
 def register_installers(context):
     context.set_installer(PIP_INSTALLER, PipInstaller())
@@ -70,6 +84,41 @@ def get_pip_command():
     return None
 
 
+def externally_managed_installable():
+    """
+    PEP 668 enacted in Python 3.11 blocks pip from working in "externally
+    managed" envrionments such operating systems with included package
+    managers. If we're on Python 3.11 or greater, we need to check that pip
+    is configured to allow installing system-wide packages with the
+    flagrantly named "break system packages" config option or environment
+    variable.
+    """
+    if sys.version_info >= (3, 11):
+        if 'PIP_BREAK_SYSTEM_PACKAGES' in os.environ and os.environ[
+            'PIP_BREAK_SYSTEM_PACKAGES'
+        ].lower() in ('yes', '1', 'true'):
+            return True
+        # Check the same configuration directories as pip does per
+        # https://pip.pypa.io/en/stable/topics/configuration/
+        pip_config = ConfigParser()
+        if 'XDG_CONFIG_DIRS' in os.environ:
+            for xdg_dir in os.environ['XDG_CONFIG_DIRS'].split(':'):
+                pip_config_file = Path(xdg_dir) / 'pip' / 'pip.conf'
+                pip_config.read(pip_config_file)
+                if pip_config['install']['break-system-packages']:
+                    return True
+
+        fallback_config = Path('/etc/pip.conf')
+        pip_config.read(fallback_config)
+        if pip_config['install']['break-system-packages']:
+            return True
+        # On Python 3.11 and later, when no explicit configuration is present,
+        # global pip installation will not work.
+        return False
+    else:
+        return True
+
+
 def is_cmd_available(cmd):
     try:
         proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
@@ -131,6 +180,10 @@ class PipInstaller(PackageManagerInstaller):
     def __init__(self):
         super(PipInstaller, self).__init__(pip_detect, supports_depends=True)
 
+        # Pass necessary environment for pip functionality via sudo
+        if self.as_root and self.sudo_command != '':
+            self.sudo_command += ' --preserve-env=PIP_BREAK_SYSTEM_PACKAGES'
+
     def get_version_strings(self):
         pip_version = importlib_metadata.version('pip')
         # keeping the name "setuptools" for backward compatibility
@@ -145,6 +198,8 @@ def get_install_command(self, resolved, interactive=True, reinstall=False, quiet
         pip_cmd = get_pip_command()
         if not pip_cmd:
             raise InstallFailed((PIP_INSTALLER, 'pip is not installed'))
+        if not externally_managed_installable():
+            raise InstallFailed((PIP_INSTALLER, EXTERNALLY_MANAGED_EXPLAINER))
         packages = self.get_packages_to_install(resolved, reinstall=reinstall)
         if not packages:
             return []

test/test_rosdep_pip.py

@@ -67,6 +67,7 @@ def test_PipInstaller_get_depends():
     assert ['foo'] == installer.get_depends(dict(depends=['foo']))
 
 
+@patch.dict(os.environ, {'PIP_BREAK_SYSTEM_PACKAGES': '1'})
 def test_PipInstaller():
     from rosdep2 import InstallFailed
     from rosdep2.platforms.pip import PipInstaller
@@ -104,7 +105,7 @@ def test(expected_prefix, mock_method, mock_get_pip_command):
     try:
         if hasattr(os, 'geteuid'):
             with patch('rosdep2.installers.os.geteuid', return_value=1):
-                test(['sudo', '-H'])
+                test(['sudo', '-H', '--preserve-env=PIP_BREAK_SYSTEM_PACKAGES'])
             with patch('rosdep2.installers.os.geteuid', return_value=0):
                 test([])
         else: