_pluginfactory: Make list_plugins() report new display information

Now the PluginFactory.list_plugins() API also reports a human readable
explanation of where the plugin was loaded from for each plugin.

This is internally supported by an extension of the abstract
PluginOrigin.get_plugin_paths() APIs.

6 files changed, 31 insertions, 18 deletions

diff --git a/src/buildstream/_frontend/widget.py b/src/buildstream/_frontend/widget.py
index 30b85701c..4c22723d6 100644
--- a/src/buildstream/_frontend/widget.py
+++ b/src/buildstream/_frontend/widget.py
@@ -486,8 +486,8 @@ class LogLine(Widget):
 
         # Plugins
         text += self._format_plugins(
-            [p for p, _, _ in project.element_factory.list_plugins()],
-            [p for p, _, _ in project.source_factory.list_plugins()],
+            [p for p, _, _, _ in project.element_factory.list_plugins()],
+            [p for p, _, _, _ in project.source_factory.list_plugins()],
         )
 
         # Pipeline state
diff --git a/src/buildstream/_pluginfactory/pluginfactory.py b/src/buildstream/_pluginfactory/pluginfactory.py
index df950abee..f997d9017 100644
--- a/src/buildstream/_pluginfactory/pluginfactory.py
+++ b/src/buildstream/_pluginfactory/pluginfactory.py
@@ -165,10 +165,11 @@ class PluginFactory:
     #    (str): The plugin kind
     #    (type): The loaded plugin type
     #    (str): The default yaml file, if any
+    #    (str): The display string describing how the plugin was loaded
     #
-    def list_plugins(self) -> Iterator[Tuple[str, Type[Plugin], str]]:
-        for kind, (plugin_type, defaults) in self._types.items():
-            yield kind, plugin_type, defaults
+    def list_plugins(self) -> Iterator[Tuple[str, Type[Plugin], str, str]]:
+        for kind, (plugin_type, defaults, display) in self._types.items():
+            yield kind, plugin_type, defaults, display
 
     # get_plugin_paths():
     #
@@ -183,12 +184,13 @@ class PluginFactory:
     #    (str): The full path to the directory containing the plugin
     #    (str): The full path to the accompanying .yaml file containing
     #           the plugin's preferred defaults.
+    #    (str): The explanatory display string describing how this plugin was loaded
     #
     def get_plugin_paths(self, kind: str):
         try:
             origin = self._origins[kind]
         except KeyError:
-            return None, None
+            return None, None, None
 
         return origin.get_plugin_paths(kind, self._plugin_type)
 
@@ -220,7 +222,7 @@ class PluginFactory:
             # the optional accompanying .yaml file for the plugin, should
             # one have been provided.
             #
-            location, defaults = self.get_plugin_paths(kind)
+            location, defaults, display = self.get_plugin_paths(kind)
 
             if location:
 
@@ -245,10 +247,12 @@ class PluginFactory:
                 defaults = os.path.join(self._site_plugins_path, "{}.yaml".format(kind))
                 if not os.path.exists(defaults):
                     defaults = None
+                display = "core plugin"
 
-            self._types[kind] = (self._load_plugin(source, kind), defaults)
+            self._types[kind] = (self._load_plugin(source, kind), defaults, display)
 
-        return self._types[kind]
+        type_, defaults, _ = self._types[kind]
+        return type_, defaults
 
     # _load_plugin():
     #
diff --git a/src/buildstream/_pluginfactory/pluginorigin.py b/src/buildstream/_pluginfactory/pluginorigin.py
index bd987171d..e75b8cb58 100644
--- a/src/buildstream/_pluginfactory/pluginorigin.py
+++ b/src/buildstream/_pluginfactory/pluginorigin.py
@@ -133,6 +133,7 @@ class PluginOrigin:
     #    (str): The full path to the directory containing the plugin
     #    (str): The full path to the accompanying .yaml file containing
     #           the plugin's preferred defaults.
+    #    (str): The explanatory display string describing how this plugin was loaded
     #
     def get_plugin_paths(self, kind, plugin_type):
         pass
diff --git a/src/buildstream/_pluginfactory/pluginoriginjunction.py b/src/buildstream/_pluginfactory/pluginoriginjunction.py
index 476f12c38..c32a7956c 100644
--- a/src/buildstream/_pluginfactory/pluginoriginjunction.py
+++ b/src/buildstream/_pluginfactory/pluginoriginjunction.py
@@ -48,7 +48,7 @@ class PluginOriginJunction(PluginOrigin):
 
         # Now ask for the paths from the subproject PluginFactory
         try:
-            location, defaults = factory.get_plugin_paths(kind)
+            location, defaults, display = factory.get_plugin_paths(kind)
         except PluginError as e:
             # Add some context to an error raised by loading a plugin from a subproject
             #
@@ -74,7 +74,12 @@ class PluginOriginJunction(PluginOrigin):
                 reason="junction-plugin-not-found",
             )
 
-        return location, defaults
+        # Use the resolved project path for the display string rather than the user configured junction path
+        project_path = "toplevel project"
+        if project.junction:
+            project_path = project.junction._get_full_name()
+
+        return location, defaults, "junction: {} ({})".format(project_path, display)
 
     def load_config(self, origin_node):
 
diff --git a/src/buildstream/_pluginfactory/pluginoriginlocal.py b/src/buildstream/_pluginfactory/pluginoriginlocal.py
index 5cfe2fd3a..34fba09e6 100644
--- a/src/buildstream/_pluginfactory/pluginoriginlocal.py
+++ b/src/buildstream/_pluginfactory/pluginoriginlocal.py
@@ -27,21 +27,20 @@ class PluginOriginLocal(PluginOrigin):
     def __init__(self):
         super().__init__(PluginOriginType.LOCAL)
 
-        # An absolute path to where plugins from this origin are found
+        # Project relative path to where plugins from this origin are found
         self._path = None
 
     def get_plugin_paths(self, kind, plugin_type):
-        defaults = os.path.join(self._path, "{}.yaml".format(kind))
+        path = os.path.join(self.project.directory, self._path)
+        defaults = os.path.join(path, "{}.yaml".format(kind))
         if not os.path.exists(defaults):
             defaults = None
 
-        return self._path, defaults
+        return path, defaults, "project directory: {}".format(self._path)
 
     def load_config(self, origin_node):
 
         origin_node.validate_keys(["path", *PluginOrigin._COMMON_CONFIG_KEYS])
 
         path_node = origin_node.get_scalar("path")
-        path = self.project.get_path_from_node(path_node, check_is_dir=True)
-
-        self._path = os.path.join(self.project.directory, path)
+        self._path = self.project.get_path_from_node(path_node, check_is_dir=True)
diff --git a/src/buildstream/_pluginfactory/pluginoriginpip.py b/src/buildstream/_pluginfactory/pluginoriginpip.py
index 3a9c63f7e..013cd67f3 100644
--- a/src/buildstream/_pluginfactory/pluginoriginpip.py
+++ b/src/buildstream/_pluginfactory/pluginoriginpip.py
@@ -89,7 +89,11 @@ class PluginOriginPip(PluginOrigin):
             # The plugin didn't have an accompanying YAML file
             defaults = None
 
-        return os.path.dirname(location), defaults
+        return (
+            os.path.dirname(location),
+            defaults,
+            "python package '{}' at: {}".format(package.dist, package.dist.location),
+        )
 
     def load_config(self, origin_node):