Store marked directories in Artifact proto

src/buildstream/_artifact.py

@@ -325,6 +325,9 @@ def cache(
                 for key, value in sorted(sandbox_env.items()):
                     artifact.buildsandbox.environment.add(name=key, value=value)
 
+            for directory in buildsandbox._get_marked_directories():
+                artifact.buildsandbox.marked_directories.append(directory)
+
             artifact.buildsandbox.working_directory = buildsandbox._get_work_directory()
 
             for subsandbox in buildsandbox._get_subsandboxes():
@@ -699,7 +702,7 @@ def pull(self, *, pull_buildtrees):
     def configure_sandbox(self, sandbox):
         artifact = self._get_proto()
 
-        if artifact.buildsandbox and artifact.buildsandbox.environment:
+        if artifact.HasField("buildsandbox") and artifact.buildsandbox.environment:
             env = {}
             for env_var in artifact.buildsandbox.environment:
                 env[env_var.name] = env_var.value
@@ -708,8 +711,12 @@ def configure_sandbox(self, sandbox):
 
         sandbox.set_environment(env)
 
-        if artifact.buildsandbox and artifact.buildsandbox.working_directory:
-            sandbox.set_work_directory(artifact.buildsandbox.working_directory)
+        if artifact.HasField("buildsandbox"):
+            for directory in artifact.buildsandbox.marked_directories:
+                sandbox.mark_directory(directory)
+
+            if artifact.buildsandbox.working_directory:
+                sandbox.set_work_directory(artifact.buildsandbox.working_directory)
 
     #  load_proto()
     #

src/buildstream/_protos/buildstream/v2/artifact.proto

@@ -90,6 +90,7 @@ message Artifact {
     repeated build.bazel.remote.execution.v2.Command.EnvironmentVariable environment = 1;
     string working_directory = 2;
     repeated build.bazel.remote.execution.v2.Digest subsandbox_digests = 3;
+    repeated string marked_directories = 4;
   };
   SandboxState buildsandbox = 18;  // optional
 }

src/buildstream/_protos/buildstream/v2/artifact_pb2.pyi

@@ -28,14 +28,16 @@ class Artifact(_message.Message):
         digest: _remote_execution_pb2.Digest
         def __init__(self, name: _Optional[str] = ..., digest: _Optional[_Union[_remote_execution_pb2.Digest, _Mapping]] = ...) -> None: ...
     class SandboxState(_message.Message):
-        __slots__ = ("environment", "working_directory", "subsandbox_digests")
+        __slots__ = ("environment", "working_directory", "subsandbox_digests", "marked_directories")
         ENVIRONMENT_FIELD_NUMBER: _ClassVar[int]
         WORKING_DIRECTORY_FIELD_NUMBER: _ClassVar[int]
         SUBSANDBOX_DIGESTS_FIELD_NUMBER: _ClassVar[int]
+        MARKED_DIRECTORIES_FIELD_NUMBER: _ClassVar[int]
         environment: _containers.RepeatedCompositeFieldContainer[_remote_execution_pb2.Command.EnvironmentVariable]
         working_directory: str
         subsandbox_digests: _containers.RepeatedCompositeFieldContainer[_remote_execution_pb2.Digest]
-        def __init__(self, environment: _Optional[_Iterable[_Union[_remote_execution_pb2.Command.EnvironmentVariable, _Mapping]]] = ..., working_directory: _Optional[str] = ..., subsandbox_digests: _Optional[_Iterable[_Union[_remote_execution_pb2.Digest, _Mapping]]] = ...) -> None: ...
+        marked_directories: _containers.RepeatedScalarFieldContainer[str]
+        def __init__(self, environment: _Optional[_Iterable[_Union[_remote_execution_pb2.Command.EnvironmentVariable, _Mapping]]] = ..., working_directory: _Optional[str] = ..., subsandbox_digests: _Optional[_Iterable[_Union[_remote_execution_pb2.Digest, _Mapping]]] = ..., marked_directories: _Optional[_Iterable[str]] = ...) -> None: ...
     VERSION_FIELD_NUMBER: _ClassVar[int]
     BUILD_SUCCESS_FIELD_NUMBER: _ClassVar[int]
     BUILD_ERROR_FIELD_NUMBER: _ClassVar[int]

tests/integration/shellbuildtrees.py

@@ -339,6 +339,21 @@ def test_shell_pull_cached_buildtree(share_with_buildtrees, datafiles, cli, pull
     result.assert_success()
     assert "Hi" in result.output
 
+    # Check that the working directory is writable
+    result = cli.run(
+        project=project,
+        args=[
+            "shell",
+            "--build",
+            element_name,
+            "--use-buildtree",
+            "--",
+            "touch",
+            "foo",
+        ],
+    )
+    result.assert_success()
+
 
 #
 # Test behavior of shelling into a buildtree by its artifact name
@@ -362,8 +377,7 @@ def test_shell_pull_artifact_cached_buildtree(share_with_buildtrees, datafiles,
             artifact_name,
             "--",
             "cat",
-            # We don't preserve the working directory in artifacts, so we will be executing at /
-            "/buildstream/test/build-shell/buildtree.bst/test",
+            "test",
         ],
     )
 
@@ -373,6 +387,21 @@ def test_shell_pull_artifact_cached_buildtree(share_with_buildtrees, datafiles,
     result.assert_success()
     assert "Hi" in result.output
 
+    # Check that the working directory is writable
+    result = cli.run(
+        project=project,
+        args=[
+            "shell",
+            "--build",
+            "--use-buildtree",
+            artifact_name,
+            "--",
+            "touch",
+            "foo",
+        ],
+    )
+    result.assert_success()
+
 
 #
 # Test behavior of launching a shell and requesting to use a buildtree.