utils.py: Rework `is_main_process` to allow for running the cli in a subprocessbschubert/add-isolated-tests

This will allow us a better isolation for tests, as we would now be able
to run them in subprocesses.

2 files changed, 14 insertions, 2 deletions

diff --git a/src/buildstream/_frontend/cli.py b/src/buildstream/_frontend/cli.py
index 051f5d7f7..577761033 100644
--- a/src/buildstream/_frontend/cli.py
+++ b/src/buildstream/_frontend/cli.py
@@ -10,7 +10,7 @@ from .._exceptions import BstError, LoadError, AppError
 from .._versions import BST_FORMAT_VERSION
 from .complete import main_bashcomplete, complete_path, CompleteUnhandled
 from ..types import _CacheBuildTrees, _SchedulerErrorAction
-from ..utils import _get_compression, UtilError
+from ..utils import _get_compression, _set_as_main_process, UtilError
 
 
 ##################################################################
@@ -366,6 +366,8 @@ def cli(context, **kwargs):
 
     from .app import App
 
+    _set_as_main_process()
+
     # Create the App, giving it the main arguments
     context.obj = App.create(dict(kwargs))
     context.call_on_close(context.obj.cleanup)
diff --git a/src/buildstream/utils.py b/src/buildstream/utils.py
index b6716a29d..a3cd96d1d 100644
--- a/src/buildstream/utils.py
+++ b/src/buildstream/utils.py
@@ -56,7 +56,8 @@ _ALIAS_SEPARATOR = ":"
 _URI_SCHEMES = ["http", "https", "ftp", "file", "git", "sftp", "ssh"]
 
 # Main process pid
-_MAIN_PID = os.getpid()
+# This is expected to be set by bst `cli()`
+_MAIN_PID = None
 
 # The number of threads in the main process at startup.
 # This is 1 except for certain test environments (xdist/execnet).
@@ -770,6 +771,15 @@ def _pretty_size(size, dec_places=0):
     return "{size:g}{unit}".format(size=round(psize, dec_places), unit=unit)
 
 
+# _set_as_main_process()
+#
+# Mark the current process at the
+#
+def _set_as_main_process():
+    global _MAIN_PID
+    _MAIN_PID = os.getpid()
+
+
 # _is_main_process()
 #
 # Return whether we are in the main process or not.