plugins.py

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"""
Loads plugins.
"""

from __future__ import print_function

import sys
import traceback

import roslib
import rospkg

def load_plugins():
    """
    Finds all rxbag plugins.
    
    @return: a list of plugins
    @rtype:  list of functions which return tuples of (MessageView, TimelineRenderer, list of: message type or '*')
    """
    plugins = []

    rospack = rospkg.RosPack()
    to_check = rospack.get_depends_on('rxbag', implicit=False)

    for pkg in to_check:
        manifest = rospack.get_manifest(pkg)
        plugin_module_names = manifest.get_export('rxbag', 'plugin')

        if not plugin_module_names:
            continue
        elif len(plugin_module_names) != 1:
            print("Cannot load plugin [%s]: invalid 'plugin' attribute" % (pkg), file=sys.stderr)
            continue
        plugin_module_name = plugin_module_names[0]

        try:
            # Load that package's namespace
            roslib.load_manifest(pkg)
    
            # Import specified plugin module
            plugin_module = __import__(plugin_module_name)
            for sub_module in plugin_module_name.split('.')[1:]:
                plugin_module = getattr(plugin_module, sub_module)
    
            # Retrieve the function
            plugins_func = None
            try:
                plugins_func = getattr(plugin_module, 'get_rxbag_plugins')
            except AttributeError: pass
    
            if plugins_func:
                plugins.extend(plugins_func())
            else:
                print("Cannot load plugin [%s]: no 'get_rxbag_plugins' attribute" % (plugin_module_name), file=sys.stderr)

        except Exception as ex:
            print("Unable to load plugin [%s] from package [%s]:\n%s" % (plugin_module_name, pkg, traceback.format_exc()), file=sys.stderr)

    return plugins