## Summary When doing any `bst` operations involving an element with open workspace, BuildStream throws an `AssertionError`. Interestingly, this only happens when running `bst` interactively (i.e. when attached to a tty). This is probably a regression introduced by the "Workspaces via CAS" effort. ## Steps to reproduce ```bash # Clone https://gitlab.com/BuildStream/buildstream and cd into it # cd tests/frontend/project bst workspace open import-bin.bst --directory dir bst show import-bin.bst # Watch bst throw an assertion error # Included stack trace at the bottom # Funnily enough, the following command succeeds bst show imort-bin.bst | tee # All good! ``` ## What is the current bug behavior? `bst` throws assertion errors when running any commands on a workspaced element. ## What is the expected correct behavior? We don't get an assertion error and the command succeeds. ## Relevant logs and/or screenshots ``` # Bad /src/tests/frontend/project> bst show import-bin.bst [--:--:--][ ][ main:core activity ] START Loading elements [00:00:00][ ][ main:core activity ] SUCCESS Loading elements [--:--:--][ ][ main:core activity ] START Resolving elements [00:00:00][ ][ main:core activity ] SUCCESS Resolving elements [--:--:--][ ][ main:core activity ] START Resolving cached state [--:--:--][ ][ main:core activity ] BUG Traceback (most recent call last): File "/usr/local/bin/bst", line 8, in <module> sys.exit(cli()) File "/usr/local/lib/python3.7/site-packages/click/core.py", line 764, in __call__ return self.main(*args, **kwargs) File "/src/src/buildstream/_frontend/cli.py", line 244, in override_main standalone_mode=standalone_mode, **extra) File "/usr/local/lib/python3.7/site-packages/click/core.py", line 717, in main rv = self.invoke(ctx) File "/usr/local/lib/python3.7/site-packages/click/core.py", line 1137, in invoke return _process_result(sub_ctx.command.invoke(sub_ctx)) File "/usr/local/lib/python3.7/site-packages/click/core.py", line 956, in invoke return ctx.invoke(self.callback, **ctx.params) File "/usr/local/lib/python3.7/site-packages/click/core.py", line 555, in invoke return callback(*args, **kwargs) File "/usr/local/lib/python3.7/site-packages/click/decorators.py", line 27, in new_func return f(get_current_context().obj, *args, **kwargs) File "/src/src/buildstream/_frontend/cli.py", line 537, in show except_targets=except_) File "/src/src/buildstream/_stream.py", line 151, in load_selection load_refs=load_refs) File "/src/src/buildstream/_stream.py", line 1283, in _load self._pipeline.resolve_elements(self.targets) File "/src/src/buildstream/_pipeline.py", line 163, in resolve_elements task.add_current_progress() File "/src/src/buildstream/_state.py", line 407, in add_current_progress self.set_current_progress(new_progress) File "/src/src/buildstream/_state.py", line 392, in set_current_progress self._render_cb() File "/src/src/buildstream/_messenger.py", line 424, in _render_status self._render_status_cb() File "/src/src/buildstream/_frontend/app.py", line 503, in _maybe_render_status self._status.render() File "/src/src/buildstream/_frontend/status.py", line 141, in render text = self._header.render(self._term_width, elapsed) File "/src/src/buildstream/_frontend/status.py", line 422, in render usage = cas.get_cache_usage() File "/src/src/buildstream/_cas/cascache.py", line 1049, in get_cache_usage self._cache_usage_monitor = _CASCacheUsageMonitor(self) File "/src/src/buildstream/_cas/cascache.py", line 1112, in __init__ assert utils._is_single_threaded() and not cas.has_open_grpc_channels() AssertionError # Good /src/tests/frontend/project> bst show import-bin.bst | tee [--:--:--][ ][ main:core activity ] START Loading elements [00:00:00][ ][ main:core activity ] SUCCESS Loading elements [--:--:--][ ][ main:core activity ] START Resolving elements [00:00:00][ ][ main:core activity ] SUCCESS Resolving elements [--:--:--][ ][ main:core activity ] START Resolving cached state [00:00:01][ ][ main:core activity ] SUCCESS Resolving cached state cached 6c44373cb1ad54802520e6dbea14bedaa2f52f1db33cda96598cadd901d191a2 import-bin.bst Workspace: /src/tests/frontend/project/dir ```