Merge branch 'mablanch/447-stack-trace-checkout' into 'master'

Handle checkout failure for unbuilt elements

See merge request BuildStream/buildstream!590

3 files changed, 17 insertions, 1 deletions

diff --git a/buildstream/_stream.py b/buildstream/_stream.py
index bd4b2ccf0..ad4e1066c 100644
--- a/buildstream/_stream.py
+++ b/buildstream/_stream.py
@@ -434,7 +434,7 @@ class Stream():
 
         except BstError as e:
             raise StreamError("Error while staging dependencies into a sandbox"
-                              ": '{}'".format(e), reason=e.reason) from e
+                              ": '{}'".format(e), detail=e.detail, reason=e.reason) from e
 
     # workspace_open
     #
diff --git a/buildstream/element.py b/buildstream/element.py
index 2218ef94b..bec87815c 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -623,6 +623,12 @@ class Element(Plugin):
               dep.stage_artifact(sandbox)
         """
 
+        if not self._cached():
+            detail = "No artifacts have been cached yet for that element\n" + \
+                     "Try building the element first with `bst build`\n"
+            raise ElementError("No artifacts to stage",
+                               detail=detail, reason="uncached-checkout-attempt")
+
         if update_mtimes is None:
             update_mtimes = []
 
diff --git a/tests/frontend/buildcheckout.py b/tests/frontend/buildcheckout.py
index 1ec8f491f..f27005ada 100644
--- a/tests/frontend/buildcheckout.py
+++ b/tests/frontend/buildcheckout.py
@@ -97,6 +97,16 @@ def test_build_checkout_deps(datafiles, cli, deps):
 
 
 @pytest.mark.datafiles(DATA_DIR)
+def test_build_checkout_unbuilt(datafiles, cli):
+    project = os.path.join(datafiles.dirname, datafiles.basename)
+    checkout = os.path.join(cli.directory, 'checkout')
+
+    # Check that checking out an unbuilt element fails nicely
+    result = cli.run(project=project, args=['checkout', 'target.bst', checkout])
+    result.assert_main_error(ErrorDomain.STREAM, "uncached-checkout-attempt")
+
+
+@pytest.mark.datafiles(DATA_DIR)
 def test_build_checkout_tarball(datafiles, cli):
     project = os.path.join(datafiles.dirname, datafiles.basename)
     checkout = os.path.join(cli.directory, 'checkout.tar')