summaryrefslogtreecommitdiff
path: root/buildstream/_plugincontext.py
blob: 264adcb7967d2f18ddc58e4cf2ed4210242f0138 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
#!/usr/bin/env python3
#
#  Copyright (C) 2016 Codethink Limited
#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU Lesser General Public
#  License as published by the Free Software Foundation; either
#  version 2 of the License, or (at your option) any later version.
#
#  This library is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the GNU
#  Lesser General Public License for more details.
#
#  You should have received a copy of the GNU Lesser General Public
#  License along with this library. If not, see <http://www.gnu.org/licenses/>.
#
#  Authors:
#        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>

import os
import inspect

from ._exceptions import PluginError
from . import utils


# A Context for loading plugin types
#
# Args:
#     plugin_base (PluginBase): The main PluginBase object to work with
#     base_type (type):         A base object type for this context
#     site_plugin_path (str):   Path to where buildstream keeps plugins
#     plugin_origins (list):    Data used to search for plugins
#
# Since multiple pipelines can be processed recursively
# within the same interpretor, it's important that we have
# one context associated to the processing of a given pipeline,
# this way sources and element types which are particular to
# a given BuildStream project are isolated to their respective
# Pipelines.
#
class PluginContext():

    def __init__(self, plugin_base, base_type, site_plugin_path, plugin_origins=None, dependencies=None):

        self.dependencies = dependencies
        self.loaded_dependencies = []
        self.base_type = base_type  # The base class plugins derive from
        self.types = {}             # Plugin type lookup table by kind
        self.plugin_origins = plugin_origins or []

        # The PluginSource object
        self.plugin_base = plugin_base
        self.site_source = plugin_base.make_plugin_source(searchpath=site_plugin_path)
        self.alternate_sources = {}

    # lookup():
    #
    # Fetches a type loaded from a plugin in this plugin context
    #
    # Args:
    #     kind (str): The kind of Plugin to create
    #
    # Returns: the type associated with the given kind
    #
    # Raises: PluginError
    #
    def lookup(self, kind):
        return self.ensure_plugin(kind)

    def _get_local_plugin_source(self, path):
        if ('local', path) not in self.alternate_sources:
            # key by a tuple to avoid collision
            source = self.plugin_base.make_plugin_source(searchpath=[path])
            # Ensure that sources never get garbage collected,
            # as they'll take the plugins with them.
            self.alternate_sources[('local', path)] = source
        else:
            source = self.alternate_sources[('local', path)]
        return source

    def _get_pip_plugin_source(self, package_name, kind):
        defaults = None
        if ('pip', package_name) not in self.alternate_sources:
            import pkg_resources
            # key by a tuple to avoid collision
            try:
                package = pkg_resources.get_entry_info(package_name,
                                                       'buildstream.plugins',
                                                       kind)
            except pkg_resources.DistributionNotFound as e:
                raise PluginError("Failed to load {} plugin '{}': {}"
                                  .format(self.base_type.__name__, kind, e)) from e

            if package is None:
                raise PluginError("Pip package {} does not contain a plugin named '{}'"
                                  .format(package_name, kind))

            location = package.dist.get_resource_filename(
                pkg_resources._manager,
                package.module_name.replace('.', os.sep) + '.py'
            )

            # Also load the defaults - required since setuptools
            # may need to extract the file.
            try:
                defaults = package.dist.get_resource_filename(
                    pkg_resources._manager,
                    package.module_name.replace('.', os.sep) + '.yaml'
                )
            except KeyError:
                # The plugin didn't have an accompanying YAML file
                defaults = None

            source = self.plugin_base.make_plugin_source(searchpath=[os.path.dirname(location)])
            self.alternate_sources[('pip', package_name)] = source

        else:
            source = self.alternate_sources[('pip', package_name)]

        return source, defaults

    def ensure_plugin(self, kind):

        if kind not in self.types:
            # Check whether the plugin is specified in plugins
            source = None
            defaults = None
            loaded_dependency = False
            for origin in self.plugin_origins:
                if kind not in origin['plugins']:
                    continue

                if origin['origin'] == 'local':
                    source = self._get_local_plugin_source(origin['path'])
                elif origin['origin'] == 'pip':
                    source, defaults = self._get_pip_plugin_source(origin['package-name'], kind)
                else:
                    raise PluginError("Failed to load plugin '{}': "
                                      "Unexpected plugin origin '{}'"
                                      .format(kind, origin['origin']))
                loaded_dependency = True
                break

            # Fall back to getting the source from site
            if not source:
                if kind not in self.site_source.list_plugins():
                    raise PluginError("No {} type registered for kind '{}'"
                                      .format(self.base_type.__name__, kind))

                source = self.site_source

            self.types[kind] = self.load_plugin(source, kind, defaults)
            if loaded_dependency:
                self.loaded_dependencies.append(kind)

        return self.types[kind]

    def load_plugin(self, source, kind, defaults):

        try:
            plugin = source.load_plugin(kind)

            if not defaults:
                plugin_file = inspect.getfile(plugin)
                plugin_dir = os.path.dirname(plugin_file)
                plugin_conf_name = "{}.yaml".format(kind)
                defaults = os.path.join(plugin_dir, plugin_conf_name)

        except ImportError as e:
            raise PluginError("Failed to load {} plugin '{}': {}"
                              .format(self.base_type.__name__, kind, e)) from e

        try:
            plugin_type = plugin.setup()
        except AttributeError as e:
            raise PluginError("{} plugin '{}' did not provide a setup() function"
                              .format(self.base_type.__name__, kind)) from e
        except TypeError as e:
            raise PluginError("setup symbol in {} plugin '{}' is not a function"
                              .format(self.base_type.__name__, kind)) from e

        self.assert_plugin(kind, plugin_type)
        self.assert_version(kind, plugin_type)
        return (plugin_type, defaults)

    def assert_plugin(self, kind, plugin_type):
        if kind in self.types:
            raise PluginError("Tried to register {} plugin for existing kind '{}' "
                              "(already registered {})"
                              .format(self.base_type.__name__, kind, self.types[kind].__name__))
        try:
            if not issubclass(plugin_type, self.base_type):
                raise PluginError("{} plugin '{}' returned type '{}', which is not a subclass of {}"
                                  .format(self.base_type.__name__, kind,
                                          plugin_type.__name__,
                                          self.base_type.__name__))
        except TypeError as e:
            raise PluginError("{} plugin '{}' returned something that is not a type (expected subclass of {})"
                              .format(self.base_type.__name__, kind,
                                      self.base_type.__name__)) from e

    def assert_version(self, kind, plugin_type):

        # Now assert BuildStream version
        bst_major, bst_minor = utils.get_bst_version()

        if bst_major < plugin_type.BST_REQUIRED_VERSION_MAJOR or \
           (bst_major == plugin_type.BST_REQUIRED_VERSION_MAJOR and
            bst_minor < plugin_type.BST_REQUIRED_VERSION_MINOR):
            raise PluginError("BuildStream {}.{} is too old for {} plugin '{}' (requires {}.{})"
                              .format(
                                  bst_major, bst_minor,
                                  self.base_type.__name__, kind,
                                  plugin_type.BST_REQUIRED_VERSION_MAJOR,
                                  plugin_type.BST_REQUIRED_VERSION_MINOR))