borgmatic/borgmatic/hooks/command.py

import logging
import os
import re
import shlex
import sys

import borgmatic.execute
import borgmatic.logger

logger = logging.getLogger(__name__)


SOFT_FAIL_EXIT_CODE = 75


def interpolate_context(hook_description, command, context):
    '''
    Given a config filename, a hook description, a single hook command, and a dict of context
    names/values, interpolate the values by "{name}" into the command and return the result.
    '''
    for name, value in context.items():
        command = command.replace(f'{{{name}}}', shlex.quote(str(value)))

    for unsupported_variable in re.findall(r'{\w+}', command):
        logger.warning(
            f"Variable '{unsupported_variable}' is not supported in {hook_description} hook"
        )

    return command


def make_environment(current_environment, sys_module=sys):
    '''
    Given the existing system environment as a map from environment variable name to value, return a
    copy of it, augmented with any extra environment variables that should be used when running
    command hooks.
    '''
    environment = dict(current_environment)

    # Detect whether we're running within a PyInstaller bundle. If so, set or clear LD_LIBRARY_PATH
    # based on the value of LD_LIBRARY_PATH_ORIG. This prevents library version information errors.
    if getattr(sys_module, 'frozen', False) and hasattr(sys_module, '_MEIPASS'):
        environment['LD_LIBRARY_PATH'] = environment.get('LD_LIBRARY_PATH_ORIG', '')

    return environment


def filter_hooks(command_hooks, before=None, after=None, hook_name=None, action_names=None):
    '''
    Given a sequence of command hook dicts from configuration and one or more filters (before name,
    after name, calling hook name, or a sequence of action names), filter down the command hooks to
    just the ones that match the given filters.
    '''
    return tuple(
        hook_config
        for hook_config in command_hooks
        for config_hook_names in (hook_config.get('hooks'),)
        for config_action_names in (hook_config.get('when'),)
        if before is None or hook_config.get('before') == before
        if after is None or hook_config.get('after') == after
        if hook_name is None or config_hook_names is None or hook_name in config_hook_names
        if action_names is None or config_action_names is None or set(config_action_names or ()).intersection(set(action_names))
    )


def execute_hooks(command_hooks, umask, dry_run, **context):
    '''
    Given a sequence of command hook dicts from configuration, a umask to execute with (or None),
    and whether this is a dry run, run the commands for each hook. Or don't run them if this is a
    dry run.

    The context contains optional values interpolated by name into the hook commands.

    Raise ValueError if the umask cannot be parsed or a hook is invalid.
    Raise subprocesses.CalledProcessError if an error occurs in a hook.
    '''
    borgmatic.logger.add_custom_log_levels()

    dry_run_label = ' (dry run; not actually running hooks)' if dry_run else ''

    for hook_config in command_hooks:
        commands = hook_config.get('run')

        if 'before' in hook_config:
            description = f'before {hook_config.get("before")}'
        elif 'after' in hook_config:
            description = f'after {hook_config.get("after")}'
        else:
            raise ValueError('Invalid hook configuration: {hook_config}')

        if not commands:
            logger.debug(f'No commands to run for {description} hook')
            return

        commands = [interpolate_context(description, command, context) for command in commands]

        if len(commands) == 1:
            logger.info(f'Running command for {description} hook{dry_run_label}')
        else:
            logger.info(
                f'Running {len(commands)} commands for {description} hook{dry_run_label}',
            )

        if umask:
            parsed_umask = int(str(umask), 8)
            logger.debug(f'Setting hook umask to {oct(parsed_umask)}')
            original_umask = os.umask(parsed_umask)
        else:
            original_umask = None

        try:
            for command in commands:
                if dry_run:
                    continue

                borgmatic.execute.execute_command(
                    [command],
                    output_log_level=(logging.ERROR if hook_config.get('after') == 'error' else logging.ANSWER),
                    shell=True,
                    environment=make_environment(os.environ),
                )
        finally:
            if original_umask:
                os.umask(original_umask)


def considered_soft_failure(error):
    '''
    Given a configuration filename and an exception object, return whether the exception object
    represents a subprocess.CalledProcessError with a return code of SOFT_FAIL_EXIT_CODE. If so,
    that indicates that the error is a "soft failure", and should not result in an error.
    '''
    exit_code = getattr(error, 'returncode', None)
    if exit_code is None:
        return False

    if exit_code == SOFT_FAIL_EXIT_CODE:
        logger.info(
            f'Command hook exited with soft failure exit code ({SOFT_FAIL_EXIT_CODE}); skipping remaining repository actions',
        )
        return True

    return False