bitbake: cooker/cookerdata/utils: Improve context management

The current execution context management for bitbake is ugly and the
use of a global variable is nasty. Fixing that is hard, however we
can improve things to start to establish an API for accessing
and changing that context.

This patch also adds in an explicit reset of the context when we reparse
the configuration data which starts to improve the lifecycle of the data
in setups like hob.

(Bitbake rev: 6c3281a140125337fc75783973485e16785d05a1)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/cooker.py

@@ -1454,7 +1454,7 @@ class Parser(multiprocessing.Process):
         self.quit = quit
         self.init = init
         multiprocessing.Process.__init__(self)
-        self.context = bb.utils._context.copy()
+        self.context = bb.utils.get_context().copy()
         self.handlers = bb.event._handlers.copy()
 
     def run(self):
@@ -1490,7 +1490,8 @@ class Parser(multiprocessing.Process):
 
     def parse(self, filename, appends, caches_array):
         try:
-            bb.utils._context = self.context.copy()
+            # Reset our environment and handlers to the original settings
+            bb.utils.set_context(self.context.copy())
             bb.event._handlers = self.handlers.copy()
             return True, bb.cache.Cache.parse(filename, appends, self.cfg, caches_array)
         except Exception as exc:

bitbake/lib/bb/cookerdata.py

@@ -173,6 +173,7 @@ class CookerDataBuilder(object):
         self.postfiles = params.postfile
         self.tracking = params.tracking
 
+        bb.utils.set_context(bb.utils.clean_context())
         self.data = bb.data.init()
         if self.tracking:
             self.data.enableTracking()

bitbake/lib/bb/utils.py

@@ -36,12 +36,22 @@ from contextlib import contextmanager
 
 logger = logging.getLogger("BitBake.Util")
 
+def clean_context():
+    return {
+        "os": os,
+        "bb": bb,
+        "time": time,
+    }
+
+def get_context():
+    return _context
+    
+
+def set_context(ctx):
+    _context = ctx
+
 # Context used in better_exec, eval
-_context = {
-    "os": os,
-    "bb": bb,
-    "time": time,
-}
+_context = clean_context()
 
 def explode_version(s):
     r = []
@@ -343,7 +353,7 @@ def better_exec(code, context, text = None, realfile = "<code>"):
     if not hasattr(code, "co_filename"):
         code = better_compile(code, realfile, realfile)
     try:
-        exec(code, _context, context)
+        exec(code, get_context(), context)
     except Exception as e:
         (t, value, tb) = sys.exc_info()
 
@@ -358,10 +368,10 @@ def better_exec(code, context, text = None, realfile = "<code>"):
         raise e
 
 def simple_exec(code, context):
-    exec(code, _context, context)
+    exec(code, get_context(), context)
 
 def better_eval(source, locals):
-    return eval(source, _context, locals)
+    return eval(source, get_context(), locals)
 
 @contextmanager
 def fileslocked(files):