ubuntu-advantage: Add new config module to support ubuntu-advantage-tools

ubuntu-advantage-tools is a package for enabling and disabling extended
support services such as Extended Security Maintenance (ESM), Canonical
Livepatch and FIPS certified PPAs. Simplify Ubuntu Advantage setup on
machines by allowing users to provide a list of ubuntu-advantage commands
in cloud-config.

1 files changed, 57 insertions, 0 deletions

diff --git a/cloudinit/subp.py b/cloudinit/subp.py
new file mode 100644
index 00000000..0ad09306
--- /dev/null
+++ b/cloudinit/subp.py
@@ -0,0 +1,57 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+"""Common utility functions for interacting with subprocess."""
+
+# TODO move subp shellify and runparts related functions out of util.py
+
+import logging
+
+LOG = logging.getLogger(__name__)
+
+
+def prepend_base_command(base_command, commands):
+    """Ensure user-provided commands start with base_command; warn otherwise.
+
+    Each command is either a list or string. Perform the following:
+       - If the command is a list, pop the first element if it is None
+       - If the command is a list, insert base_command as the first element if
+         not present.
+       - When the command is a string not starting with 'base-command', warn.
+
+    Allow flexibility to provide non-base-command environment/config setup if
+    needed.
+
+    @commands: List of commands. Each command element is a list or string.
+
+    @return: List of 'fixed up' commands.
+    @raise: TypeError on invalid config item type.
+    """
+    warnings = []
+    errors = []
+    fixed_commands = []
+    for command in commands:
+        if isinstance(command, list):
+            if command[0] is None:  # Avoid warnings by specifying None
+                command = command[1:]
+            elif command[0] != base_command:  # Automatically prepend
+                command.insert(0, base_command)
+        elif isinstance(command, str):
+            if not command.startswith('%s ' % base_command):
+                warnings.append(command)
+        else:
+            errors.append(str(command))
+            continue
+        fixed_commands.append(command)
+
+    if warnings:
+        LOG.warning(
+            'Non-%s commands in %s config:\n%s',
+            base_command, base_command, '\n'.join(warnings))
+    if errors:
+        raise TypeError(
+            'Invalid {name} config.'
+            ' These commands are not a string or list:\n{errors}'.format(
+                name=base_command, errors='\n'.join(errors)))
+    return fixed_commands
+
+
+# vi: ts=4 expandtab