[yocto-autobuilder2][RFC] master.cfg: Replace pkg_resources with importlib.metadata

pkg_resources (from setuptools) is deprecated. Replace the fake
Distribution/EntryPoint/working_set manipulation with
importlib.metadata equivalents:

- Intercept importlib.metadata.version() for the local plugin, since
  buildbot's Application() calls it at import time before the plugin
  is registered.
- Use importlib.metadata.EntryPoint directly instead of the old
  pkg_resources.EntryPoint.parse() plus fake Distribution approach.
- Remove the now-unused os import.

Signed-off-by: Tim Orling <[email protected]>
---
This has been working for me on my local AB cluster, where the
controller is running on a Debian 13 AMD Ryzen system.

 master.cfg | 61 +++++++++++++++++++++++++++---------------------------
 1 file changed, 31 insertions(+), 30 deletions(-)

diff --git a/master.cfg b/master.cfg
index 63119ca..55312ef 100644
--- a/master.cfg
+++ b/master.cfg
@@ -1,46 +1,47 @@
 # -*- python -*-
 # ex: set filetype=python:
 
-import os
 import importlib
-import pkg_resources
-
-from buildbot.plugins import *
-from buildbot.plugins import db
-from yoctoabb import builders, config, schedulers, workers, services, www
+import importlib.metadata
+from importlib.metadata import EntryPoint
 
 #
-# Prepare to feel ill
+# Buildbot discovers www plugins via entry points. Since the yocto_console_view
+# plugin lives in this repo rather than being installed as a package, we need
+# two workarounds:
 #
-# Buildbot uses plugins from pkg_resources, i.e. things which are installed
-# For the Yocto autobuilder, we want the plugin from this repo/directory.
+# 1. Buildbot's Application() calls importlib.metadata.version() at import
+#    time, so we intercept that to return a version for our local plugin
+#    before any yoctoabb imports occur.
 #
-# Firstly we therefore have to create a dummy pkg_resources entry/distribution
-# which we add into the global working set. Ugly. It gets worse.
+# 2. The get_plugins('www') call from www/service.py happens before this
+#    master.cfg file is parsed, so we create an EntryPoint directly and
+#    register it into buildbot's internal plugin DB.
 #
-# The get_plugins('www') call from www/service.py happens before this
-# master.cfg file is parsed, which means our plugin won't be found. There
-# is no API to rescan for plugins. We therefore so some horrible internal
-# API monkey patching to add ourselves into the internal list.
 
-# Create a fake distribution to insert into the global working_set
-us = os.path.dirname(os.path.realpath(__file__))
-d = pkg_resources.Distribution(us + "/yocto_console_view", metadata=None, project_name="yocto_console_view", version="0.0.1")
+# Handle importlib.metadata.version() for our uninstalled local plugin.
+# This must happen before importing yoctoabb, since that triggers
+# Application().__init__ which calls importlib.metadata.version().
+_orig_metadata_version = importlib.metadata.version
+def _local_metadata_version(name):
+    if name == 'yoctoabb.yocto_console_view.yocto_console_view':
+        return '0.0.1'
+    return _orig_metadata_version(name)
+importlib.metadata.version = _local_metadata_version
 
-# Create the fake entry point definition
-ep = pkg_resources.EntryPoint.parse("yocto_console_view = yoctoabb.yocto_console_view.yocto_console_view:ep", dist=d)
-
-# Add the mapping to the fake EntryPoint
-d._ep_map = {'buildbot.www': {'yocto_console_view': ep}}
+from buildbot.plugins import *
+from buildbot.plugins import db
+from yoctoabb import builders, config, schedulers, workers, services, www
 
-# Add the fake distribution to the global working_set
-pkg_resources.working_set.add(d)
+ep_entry = EntryPoint(
+    name='yocto_console_view',
+    value='yoctoabb.yocto_console_view.yocto_console_view:ep',
+    group='buildbot.www'
+)
 
-# Now monkey patch us into buildbot's plugins DB
-for entry in pkg_resources.iter_entry_points('buildbot.www'):
-    if entry.name == "yocto_console_view":
-        plugindb = db._DB._namespaces['www']
-        plugindb._real_tree.add(entry.name, db._PluginEntry('buildbot.www', entry, plugindb._load_entry))
+# Register the plugin directly into buildbot's plugin DB
+plugindb = db._DB._namespaces['www']
+plugindb._real_tree.add(ep_entry.name, db._PluginEntry('buildbot.www', ep_entry, plugindb._load_entry))
 
 
 # supports re-loading configuration with buildbot sighup, meaning we can change
-- 
2.50.1 (Apple Git-155)