Merge branch 'tristan/fix-missing-workspace-artifact' into 'master'

element.py: Reset workspace state if last successful build is missing.

Closes #1017

See merge request BuildStream/buildstream!1328

3 files changed, 54 insertions, 5 deletions

diff --git a/buildstream/element.py b/buildstream/element.py
index 8cc25fec6..cc31d3f02 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -738,8 +738,24 @@ class Element(Plugin):
         context = self._get_context()
 
         if self.__can_build_incrementally() and workspace.last_successful:
-            last_successful = Artifact(self, context, strong_key=workspace.last_successful)
-            old_dep_keys = last_successful.get_metadata_dependencies()
+
+            # Try to perform an incremental build if the last successful
+            # build is still in the artifact cache
+            #
+            if self.__artifacts.contains(self, workspace.last_successful):
+                last_successful = Artifact(self, context, strong_key=workspace.last_successful)
+                old_dep_keys = last_successful.get_metadata_dependencies()
+            else:
+                # Last successful build is no longer in the artifact cache,
+                # so let's reset it and perform a full build now.
+                workspace.prepared = False
+                workspace.last_successful = None
+
+                self.info("Resetting workspace state, last successful build is no longer in the cache")
+
+                # In case we are staging in the main process
+                if utils._is_main_process():
+                    context.get_workspaces().save_config()
 
         for dep in self.dependencies(scope):
             # If we are workspaced, and we therefore perform an
@@ -764,7 +780,7 @@ class Element(Plugin):
                     # In case we are running `bst shell`, this happens in the
                     # main process and we need to update the workspace config
                     if utils._is_main_process():
-                        self._get_context().get_workspaces().save_config()
+                        context.get_workspaces().save_config()
 
             result = dep.stage_artifact(sandbox,
                                         path=path,
diff --git a/buildstream/testing/runcli.py b/buildstream/testing/runcli.py
index 72bdce09e..934c31236 100644
--- a/buildstream/testing/runcli.py
+++ b/buildstream/testing/runcli.py
@@ -637,8 +637,8 @@ class TestArtifact():
     def remove_artifact_from_cache(self, cache_dir, element_name):
 
         cache_dir = os.path.join(cache_dir, 'cas', 'refs', 'heads')
-
-        cache_dir = os.path.splitext(os.path.join(cache_dir, 'test', element_name))[0]
+        normal_name = element_name.replace(os.sep, '-')
+        cache_dir = os.path.splitext(os.path.join(cache_dir, 'test', normal_name))[0]
         shutil.rmtree(cache_dir)
 
     # is_cached():
diff --git a/tests/integration/workspace.py b/tests/integration/workspace.py
index 4ee0050d7..134ed6385 100644
--- a/tests/integration/workspace.py
+++ b/tests/integration/workspace.py
@@ -271,3 +271,36 @@ def test_incremental_configure_commands_run_only_once(cli, datafiles):
     res = cli.run(project=project, args=['build', element_name])
     res.assert_success()
     assert not os.path.exists(os.path.join(workspace, 'prepared-again'))
+
+
+# Test that rebuilding an already built workspaced element does
+# not crash after the last successfully built artifact is removed
+# from the cache
+#
+# A user can remove their artifact cache, or manually remove the
+# artifact with `bst artifact delete`, or BuildStream can delete
+# the last successfully built artifact for this workspace as a
+# part of a cleanup job.
+#
+@pytest.mark.datafiles(DATA_DIR)
+@pytest.mark.skipif(not HAVE_SANDBOX, reason='Only available with a functioning sandbox')
+def test_workspace_missing_last_successful(cli, datafiles):
+    project = str(datafiles)
+    workspace = os.path.join(cli.directory, 'workspace')
+    element_name = 'workspace/workspace-commanddir.bst'
+
+    # Open workspace
+    res = cli.run(project=project, args=['workspace', 'open', '--directory', workspace, element_name])
+    assert res.exit_code == 0
+
+    # Build first, this will record the last successful build in local state
+    res = cli.run(project=project, args=['build', element_name])
+    assert res.exit_code == 0
+
+    # Remove the artifact from the cache, invalidating the last successful build
+    res = cli.run(project=project, args=['artifact', 'delete', element_name])
+    assert res.exit_code == 0
+
+    # Build again, ensure we dont crash just because the artifact went missing
+    res = cli.run(project=project, args=['build', element_name])
+    assert res.exit_code == 0