Add BST_VIRTUAL_DIRECTORY flag for element plugins

2 files changed, 19 insertions, 4 deletions

diff --git a/buildstream/element.py b/buildstream/element.py
index e9cbdb63e..1f985aeb2 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -191,6 +191,13 @@ class Element(Plugin):
     *Since: 1.2*
     """
 
+    BST_VIRTUAL_DIRECTORY = False
+    """Whether to raise exceptions if an element uses Sandbox.get_directory
+    instead of Sandbox.get_virtual_directory.
+
+    *Since: 1.2*
+    """
+
     def __init__(self, context, project, artifacts, meta, plugin_conf):
 
         self.__cache_key_dict = None            # Dict for cache key calculation
@@ -2043,7 +2050,8 @@ class Element(Plugin):
                                               directory,
                                               stdout=stdout,
                                               stderr=stderr,
-                                              config=config)
+                                              config=config,
+                                              allow_real_directory=not self.BST_VIRTUAL_DIRECTORY)
             yield sandbox
 
         else:
diff --git a/buildstream/sandbox/sandbox.py b/buildstream/sandbox/sandbox.py
index 7e1e32b65..7e73e0d9a 100644
--- a/buildstream/sandbox/sandbox.py
+++ b/buildstream/sandbox/sandbox.py
@@ -29,7 +29,7 @@ See also: :ref:`sandboxing`.
 """
 
 import os
-from .._exceptions import ImplError
+from .._exceptions import ImplError, BstError
 
 
 class SandboxFlags():
@@ -90,6 +90,8 @@ class Sandbox():
         self.__cwd = None
         self.__env = None
         self.__mount_sources = {}
+        self.__allow_real_directory = kwargs['allow_real_directory']
+
         # Configuration from kwargs common to all subclasses
         self.__config = kwargs['config']
         self.__stdout = kwargs['stdout']
@@ -106,12 +108,17 @@ class Sandbox():
         """Fetches the sandbox root directory
 
         The root directory is where artifacts for the base
-        runtime environment should be staged.
+        runtime environment should be staged. Only works if
+        BST_VIRTUAL_DIRECTORY is not set.
 
         Returns:
            (str): The sandbox root directory
+
         """
-        return self.__root
+        if self.__allow_real_directory:
+            return self.__root
+        else:
+            raise BstError("You can't use get_directory")
 
     def set_environment(self, environment):
         """Sets the environment variables for the sandbox