Plugins: Update entrypoint group for pip origin

As discussed in
https://mail.gnome.org/archives/buildstream-list/2020-January/msg00001.html,
separate the entry point groups for elements and sources. Previously,
both used `buildstream.plugins` which meant that it wasn't possible to
have an element and a source plugin with the same name, when using `pip`
origin.

This a breaking change for all plugins, but will only affect projects
using the `pip` plugin origin.

As part of this, also bump the version of bst-plugins-experimental used
in our tests to avoid CI breakages.

4 files changed, 14 insertions, 4 deletions

diff --git a/src/buildstream/_elementfactory.py b/src/buildstream/_elementfactory.py
index 5d219c627..89e01a885 100644
--- a/src/buildstream/_elementfactory.py
+++ b/src/buildstream/_elementfactory.py
@@ -36,6 +36,7 @@ class ElementFactory(PluginContext):
             plugin_base,
             Element,
             [_site.element_plugins],
+            "buildstream.plugins.elements",
             plugin_origins=plugin_origins,
             format_versions=format_versions,
         )
diff --git a/src/buildstream/_plugincontext.py b/src/buildstream/_plugincontext.py
index 54839e16b..295482574 100644
--- a/src/buildstream/_plugincontext.py
+++ b/src/buildstream/_plugincontext.py
@@ -30,6 +30,7 @@ from . import utils
 #     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
+#     entrypoint_group (str):   Name of the entry point group that provides plugins
 #     plugin_origins (list):    Data used to search for plugins
 #     format_versions (dict):   A dict of meta.kind to the integer minimum
 #                               version number for each plugin to be loaded
@@ -42,7 +43,9 @@ from . import utils
 # Pipelines.
 #
 class PluginContext:
-    def __init__(self, plugin_base, base_type, site_plugin_path, *, plugin_origins=None, format_versions={}):
+    def __init__(
+        self, plugin_base, base_type, site_plugin_path, entrypoint_group, *, plugin_origins=None, format_versions={}
+    ):
 
         # For pickling across processes, make sure this context has a unique
         # identifier, which we prepend to the identifier of each PluginSource.
@@ -63,6 +66,7 @@ class PluginContext:
         # The PluginSource object
         self._plugin_base = plugin_base
         self._site_plugin_path = site_plugin_path
+        self._entrypoint_group = entrypoint_group
         self._alternate_sources = {}
         self._format_versions = format_versions
 
@@ -147,7 +151,7 @@ class PluginContext:
 
             # key by a tuple to avoid collision
             try:
-                package = pkg_resources.get_entry_info(package_name, "buildstream.plugins", kind)
+                package = pkg_resources.get_entry_info(package_name, self._entrypoint_group, kind)
             except pkg_resources.DistributionNotFound as e:
                 raise PluginError("Failed to load {} plugin '{}': {}".format(self._base_type.__name__, kind, e)) from e
 
diff --git a/src/buildstream/_sourcefactory.py b/src/buildstream/_sourcefactory.py
index 7c90042a8..254c482d6 100644
--- a/src/buildstream/_sourcefactory.py
+++ b/src/buildstream/_sourcefactory.py
@@ -33,7 +33,12 @@ class SourceFactory(PluginContext):
     def __init__(self, plugin_base, *, format_versions={}, plugin_origins=None):
 
         super().__init__(
-            plugin_base, Source, [_site.source_plugins], format_versions=format_versions, plugin_origins=plugin_origins
+            plugin_base,
+            Source,
+            [_site.source_plugins],
+            "buildstream.plugins.sources",
+            format_versions=format_versions,
+            plugin_origins=plugin_origins,
         )
 
     # create():
diff --git a/tox.ini b/tox.ini
index efb91e75b..30075ee8e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -8,7 +8,7 @@ isolated_build = true
 
 # Configuration variables to share across environments
 [config]
-BST_PLUGINS_EXPERIMENTAL_VERSION = 0.14.0
+BST_PLUGINS_EXPERIMENTAL_VERSION = 0.15.0
 
 #
 # Defaults for all environments