_artifact.py: Do not create empty buildtree directories

Creating an empty buildtree directory when buildtree caching is disabled
means cached_buildtree() can return True even if no buildtree is
available, which breaks logic in the frontend and in Stream.

This adds the buildtree_exists() method to indicate whether an artifact
was created with a buildtree, independent of whether the buildtree is
available in the local cache.

2 files changed, 9 insertions, 13 deletions

diff --git a/tests/integration/artifact.py b/tests/integration/artifact.py
index 35e7f56ae..98c6ce13f 100644
--- a/tests/integration/artifact.py
+++ b/tests/integration/artifact.py
@@ -77,23 +77,20 @@ def test_cache_buildtrees(cli, tmpdir, datafiles):
         assert cli.get_element_state(project, element_name) == 'cached'
         assert share1.has_artifact('test', element_name, cli.get_element_key(project, element_name))
 
-        # The extracted buildtree dir should be empty, as we set the config
-        # to not cache buildtrees
+        # The buildtree dir should not exist, as we set the config to not cache buildtrees.
         cache_key = cli.get_element_key(project, element_name)
         elementdigest = share1.has_artifact('test', element_name, cache_key)
         with cas_extract_buildtree(elementdigest) as buildtreedir:
-            assert os.path.isdir(buildtreedir)
-            assert not os.listdir(buildtreedir)
+            assert not os.path.isdir(buildtreedir)
 
         # Delete the local cached artifacts, and assert the when pulled with --pull-buildtrees
-        # that is was cached in share1 as expected with an empty buildtree dir
+        # that is was cached in share1 as expected without a buildtree dir
         shutil.rmtree(os.path.join(str(tmpdir), 'cas'))
         assert cli.get_element_state(project, element_name) != 'cached'
         result = cli.run(project=project, args=['--pull-buildtrees', 'artifact', 'pull', element_name])
         assert element_name in result.get_pulled_elements()
         with cas_extract_buildtree(elementdigest) as buildtreedir:
-            assert os.path.isdir(buildtreedir)
-            assert not os.listdir(buildtreedir)
+            assert not os.path.isdir(buildtreedir)
         shutil.rmtree(os.path.join(str(tmpdir), 'cas'))
 
         # Assert that the default behaviour of pull to not include buildtrees on the artifact
@@ -148,5 +145,4 @@ def test_cache_buildtrees(cli, tmpdir, datafiles):
         cache_key = cli.get_element_key(project, element_name)
         elementdigest = share3.has_artifact('test', element_name, cache_key)
         with cas_extract_buildtree(elementdigest) as buildtreedir:
-            assert os.path.isdir(buildtreedir)
-            assert not os.listdir(buildtreedir)
+            assert not os.path.isdir(buildtreedir)
diff --git a/tests/integration/shellbuildtrees.py b/tests/integration/shellbuildtrees.py
index 13d21548e..31af8a0e4 100644
--- a/tests/integration/shellbuildtrees.py
+++ b/tests/integration/shellbuildtrees.py
@@ -71,8 +71,8 @@ def test_buildtree_staged_warn_empty_cached(cli_integration, tmpdir, datafiles):
     res = cli_integration.run(project=project, args=[
         'shell', '--build', '--use-buildtree', 'always', element_name, '--', 'cat', 'test'
     ])
-    res.assert_shell_error()
-    assert "Artifact contains an empty buildtree" in res.stderr
+    res.assert_main_error(ErrorDomain.APP, None)
+    assert "Artifact was created without buildtree" in res.stderr
 
 
 @pytest.mark.datafiles(DATA_DIR)
@@ -148,8 +148,8 @@ def test_buildtree_from_failure_option_never(cli_integration, tmpdir, datafiles)
     res = cli_integration.run(project=project, args=[
         'shell', '--build', element_name, '--use-buildtree', 'always', '--', 'cat', 'test'
     ])
-    res.assert_shell_error()
-    assert "Artifact contains an empty buildtree" in res.stderr
+    res.assert_main_error(ErrorDomain.APP, None)
+    assert "Artifact was created without buildtree" in res.stderr
 
 
 @pytest.mark.datafiles(DATA_DIR)