Refactor CLI importscompletion-optimizations

This reduces the number of unconditional imports, mainly to speed up
bash completion.

5 files changed, 721 insertions, 700 deletions

diff --git a/buildstream/__init__.py b/buildstream/__init__.py
index 733350bdd..771ba0c52 100644
--- a/buildstream/__init__.py
+++ b/buildstream/__init__.py
@@ -19,11 +19,13 @@
 #        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
 
 # Plugin author facing APIs
-from .__version__ import __version__
-from .utils import UtilError, ProgramNotFoundError
-from .sandbox import Sandbox, SandboxFlags
-from .plugin import Plugin
-from .source import Source, SourceError, Consistency
-from .element import Element, ElementError, Scope
-from .buildelement import BuildElement
-from .scriptelement import ScriptElement
+import os
+if "_BST_COMPLETION" not in os.environ:
+    from .__version__ import __version__
+    from .utils import UtilError, ProgramNotFoundError
+    from .sandbox import Sandbox, SandboxFlags
+    from .plugin import Plugin
+    from .source import Source, SourceError, Consistency
+    from .element import Element, ElementError, Scope
+    from .buildelement import BuildElement
+    from .scriptelement import ScriptElement
diff --git a/buildstream/_frontend/__init__.py b/buildstream/_frontend/__init__.py
index c2ec383c3..b2e41301e 100644
--- a/buildstream/_frontend/__init__.py
+++ b/buildstream/_frontend/__init__.py
@@ -17,8 +17,10 @@
 #
 #  Authors:
 #        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
+import os
+from .cli import cli
 
-from .profile import Profile
-from .status import Status
-from .widget import LogLine
-from .main import cli
+if "_BST_COMPLETION" not in os.environ:
+    from .profile import Profile
+    from .status import Status
+    from .widget import LogLine
diff --git a/buildstream/_frontend/cli.py b/buildstream/_frontend/cli.py
new file mode 100644
index 000000000..512966b8b
--- /dev/null
+++ b/buildstream/_frontend/cli.py
@@ -0,0 +1,702 @@
+import os
+import sys
+
+import click
+from .. import _yaml
+from .._exceptions import BstError, PipelineError, LoadError
+from ..__version__ import __version__ as build_stream_version
+from .complete import main_bashcomplete, complete_path, CompleteUnhandled
+
+
+##################################################################
+#            Override of click's main entry point                #
+##################################################################
+
+# Special completion for completing the bst elements in a project dir
+def complete_target(args, incomplete):
+    """
+    :param args: full list of args typed before the incomplete arg
+    :param incomplete: the incomplete text to autocomplete
+    :return: all the possible user-specified completions for the param
+    """
+
+    # First resolve the directory, in case there is an
+    # active --directory/-C option
+    #
+    base_directory = '.'
+    idx = -1
+    try:
+        idx = args.index('-C')
+    except ValueError:
+        try:
+            idx = args.index('--directory')
+        except ValueError:
+            pass
+
+    if idx >= 0 and len(args) > idx + 1:
+        base_directory = args[idx + 1]
+
+    # Now parse the project.conf just to find the element path,
+    # this is unfortunately a bit heavy.
+    project_file = os.path.join(base_directory, 'project.conf')
+    try:
+        project = _yaml.load(project_file)
+    except LoadError:
+        # If there is no project directory in context, just dont
+        # even bother trying to complete anything.
+        return []
+
+    # The project is not required to have an element-path
+    element_directory = project.get('element-path')
+
+    # If a project was loaded, use it's element-path to
+    # adjust our completion's base directory
+    if element_directory:
+        base_directory = os.path.join(base_directory, element_directory)
+
+    return complete_path("File", incomplete, base_directory=base_directory)
+
+
+def override_completions(cmd_param, args, incomplete):
+    """
+    :param cmd_param: command definition
+    :param args: full list of args typed before the incomplete arg
+    :param incomplete: the incomplete text to autocomplete
+    :return: all the possible user-specified completions for the param
+    """
+
+    # We can't easily extend click's data structures without
+    # modifying click itself, so just do some weak special casing
+    # right here and select which parameters we want to handle specially.
+    if isinstance(cmd_param.type, click.Path) and \
+       (cmd_param.name == 'elements' or
+        cmd_param.name == 'element' or
+        cmd_param.name == 'except_' or
+        cmd_param.opts == ['--track'] or
+        cmd_param.opts == ['--track-except']):
+        return complete_target(args, incomplete)
+
+    raise CompleteUnhandled()
+
+
+def override_main(self, args=None, prog_name=None, complete_var=None,
+                  standalone_mode=True, **extra):
+
+    # Hook for the Bash completion.  This only activates if the Bash
+    # completion is actually enabled, otherwise this is quite a fast
+    # noop.
+    if main_bashcomplete(self, prog_name, override_completions):
+
+        # If we're running tests we cant just go calling exit()
+        # from the main process.
+        #
+        # The below is a quicker exit path for the sake
+        # of making completions respond faster.
+        if 'BST_TEST_SUITE' not in os.environ:
+            sys.stdout.flush()
+            sys.stderr.flush()
+            os._exit(0)
+
+        # Regular client return for test cases
+        return
+
+    original_main(self, args=args, prog_name=prog_name, complete_var=None,
+                  standalone_mode=standalone_mode, **extra)
+
+
+original_main = click.BaseCommand.main
+click.BaseCommand.main = override_main
+
+
+##################################################################
+#                          Main Options                          #
+##################################################################
+@click.group(context_settings=dict(help_option_names=['-h', '--help']))
+@click.version_option(version=build_stream_version)
+@click.option('--config', '-c',
+              type=click.Path(exists=True, dir_okay=False, readable=True),
+              help="Configuration file to use")
+@click.option('--directory', '-C', default=os.getcwd(),
+              type=click.Path(exists=True, file_okay=False, readable=True),
+              help="Project directory (default: current directory)")
+@click.option('--on-error', default=None,
+              type=click.Choice(['continue', 'quit', 'terminate']),
+              help="What to do when an error is encountered")
+@click.option('--fetchers', type=click.INT, default=None,
+              help="Maximum simultaneous download tasks")
+@click.option('--builders', type=click.INT, default=None,
+              help="Maximum simultaneous build tasks")
+@click.option('--pushers', type=click.INT, default=None,
+              help="Maximum simultaneous upload tasks")
+@click.option('--network-retries', type=click.INT, default=None,
+              help="Maximum retries for network tasks")
+@click.option('--no-interactive', is_flag=True, default=False,
+              help="Force non interactive mode, otherwise this is automatically decided")
+@click.option('--verbose/--no-verbose', default=None,
+              help="Be extra verbose")
+@click.option('--debug/--no-debug', default=None,
+              help="Print debugging output")
+@click.option('--error-lines', type=click.INT, default=None,
+              help="Maximum number of lines to show from a task log")
+@click.option('--message-lines', type=click.INT, default=None,
+              help="Maximum number of lines to show in a detailed message")
+@click.option('--log-file',
+              type=click.File(mode='w', encoding='UTF-8'),
+              help="A file to store the main log (allows storing the main log while in interactive mode)")
+@click.option('--colors/--no-colors', default=None,
+              help="Force enable/disable ANSI color codes in output")
+@click.option('--strict/--no-strict', default=None, is_flag=True,
+              help="Elements must be rebuilt when their dependencies have changed")
+@click.option('--option', '-o', type=click.Tuple([str, str]), multiple=True,
+              help="Specify a project option")
+@click.pass_context
+def cli(context, **kwargs):
+    """Build and manipulate BuildStream projects
+
+    Most of the main options override options in the
+    user preferences configuration file.
+    """
+
+    from .main import App
+
+    # Create the App, giving it the main arguments
+    context.obj = App(dict(kwargs))
+    context.call_on_close(context.obj.cleanup)
+
+
+##################################################################
+#                          Build Command                         #
+##################################################################
+@cli.command(short_help="Build elements in a pipeline")
+@click.option('--all', default=False, is_flag=True,
+              help="Build elements that would not be needed for the current build plan")
+@click.option('--track', multiple=True,
+              type=click.Path(dir_okay=False, readable=True),
+              help="Specify elements to track during the build. Can be used "
+                   "repeatedly to specify multiple elements")
+@click.option('--track-all', default=False, is_flag=True,
+              help="Track all elements in the pipeline")
+@click.option('--track-except', multiple=True,
+              type=click.Path(dir_okay=False, readable=True),
+              help="Except certain dependencies from tracking")
+@click.option('--track-save', default=False, is_flag=True,
+              help="Write out the tracked references to their element files")
+@click.argument('elements', nargs=-1,
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def build(app, elements, all, track, track_save, track_all, track_except):
+    """Build elements in a pipeline"""
+
+    if track_all:
+        track = elements
+
+    app.initialize(elements, except_=track_except, rewritable=track_save,
+                   use_configured_remote_caches=True, track_elements=track,
+                   fetch_subprojects=True)
+    app.print_heading()
+    try:
+        app.pipeline.build(app.scheduler, all, track, track_save)
+        app.print_summary()
+    except PipelineError as e:
+        app.print_error(e)
+        app.print_summary()
+        sys.exit(-1)
+
+
+##################################################################
+#                          Fetch Command                         #
+##################################################################
+@cli.command(short_help="Fetch sources in a pipeline")
+@click.option('--except', 'except_', multiple=True,
+              type=click.Path(dir_okay=False, readable=True),
+              help="Except certain dependencies from fetching")
+@click.option('--deps', '-d', default='plan',
+              type=click.Choice(['none', 'plan', 'all']),
+              help='The dependencies to fetch (default: plan)')
+@click.option('--track', default=False, is_flag=True,
+              help="Track new source references before fetching")
+@click.argument('elements', nargs=-1,
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def fetch(app, elements, deps, track, except_):
+    """Fetch sources required to build the pipeline
+
+    By default this will only try to fetch sources which are
+    required for the build plan of the specified target element,
+    omitting sources for any elements which are already built
+    and available in the artifact cache.
+
+    Specify `--deps` to control which sources to fetch:
+
+    \b
+        none:  No dependencies, just the element itself
+        plan:  Only dependencies required for the build plan
+        all:   All dependencies
+    """
+
+    app.initialize(elements, except_=except_, rewritable=track,
+                   track_elements=elements if track else None,
+                   fetch_subprojects=True)
+    try:
+        dependencies = app.pipeline.deps_elements(deps)
+        app.print_heading(deps=dependencies)
+        app.pipeline.fetch(app.scheduler, dependencies, track)
+        app.print_summary()
+    except PipelineError as e:
+        app.print_error(e)
+        app.print_summary()
+        sys.exit(-1)
+
+
+##################################################################
+#                          Track Command                         #
+##################################################################
+@cli.command(short_help="Track new source references")
+@click.option('--except', 'except_', multiple=True,
+              type=click.Path(dir_okay=False, readable=True),
+              help="Except certain dependencies from tracking")
+@click.option('--deps', '-d', default='none',
+              type=click.Choice(['none', 'all']),
+              help='The dependencies to track (default: none)')
+@click.argument('elements', nargs=-1,
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def track(app, elements, deps, except_):
+    """Consults the specified tracking branches for new versions available
+    to build and updates the project with any newly available references.
+
+    By default this will track just the specified element, but you can also
+    update a whole tree of dependencies in one go.
+
+    Specify `--deps` to control which sources to track:
+
+    \b
+        none:  No dependencies, just the element itself
+        all:   All dependencies
+    """
+    app.initialize(elements, except_=except_, rewritable=True, track_elements=elements,
+                   fetch_subprojects=True)
+    try:
+        dependencies = app.pipeline.deps_elements(deps)
+        app.print_heading(deps=dependencies)
+        app.pipeline.track(app.scheduler, dependencies)
+        app.print_summary()
+    except PipelineError as e:
+        app.print_error(e)
+        app.print_summary()
+        sys.exit(-1)
+
+
+##################################################################
+#                           Pull Command                         #
+##################################################################
+@cli.command(short_help="Pull a built artifact")
+@click.option('--deps', '-d', default='none',
+              type=click.Choice(['none', 'all']),
+              help='The dependency artifacts to pull (default: none)')
+@click.option('--remote', '-r',
+              help="The URL of the remote cache (defaults to the first configured cache)")
+@click.argument('elements', nargs=-1,
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def pull(app, elements, deps, remote):
+    """Pull a built artifact from the configured remote artifact cache.
+
+    By default the artifact will be pulled one of the configured caches
+    if possible, following the usual priority order. If the `--remote` flag
+    is given, only the specified cache will be queried.
+
+    Specify `--deps` to control which artifacts to pull:
+
+    \b
+        none:  No dependencies, just the element itself
+        all:   All dependencies
+    """
+    app.initialize(elements, use_configured_remote_caches=(remote is None),
+                   add_remote_cache=remote, fetch_subprojects=True)
+    try:
+        to_pull = app.pipeline.deps_elements(deps)
+        app.pipeline.pull(app.scheduler, to_pull)
+        app.print_summary()
+    except BstError as e:
+        app.print_error(e)
+        app.print_summary()
+        sys.exit(-1)
+
+
+##################################################################
+#                           Push Command                         #
+##################################################################
+@cli.command(short_help="Push a built artifact")
+@click.option('--deps', '-d', default='none',
+              type=click.Choice(['none', 'all']),
+              help='The dependencies to push (default: none)')
+@click.option('--remote', '-r', default=None,
+              help="The URL of the remote cache (defaults to the first configured cache)")
+@click.argument('elements', nargs=-1,
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def push(app, elements, deps, remote):
+    """Push a built artifact to a remote artifact cache.
+
+    The default destination is the highest priority configured cache. You can
+    override this by passing a different cache URL with the `--remote` flag.
+
+    Specify `--deps` to control which artifacts to push:
+
+    \b
+        none:  No dependencies, just the element itself
+        all:   All dependencies
+    """
+    app.initialize(elements, use_configured_remote_caches=(remote is None),
+                   add_remote_cache=remote, fetch_subprojects=True)
+    try:
+        to_push = app.pipeline.deps_elements(deps)
+        app.pipeline.push(app.scheduler, to_push)
+        app.print_summary()
+    except BstError as e:
+        app.print_error(e)
+        app.print_summary()
+        sys.exit(-1)
+
+
+##################################################################
+#                           Show Command                         #
+##################################################################
+@cli.command(short_help="Show elements in the pipeline")
+@click.option('--except', 'except_', multiple=True,
+              type=click.Path(dir_okay=False, readable=True),
+              help="Except certain dependencies")
+@click.option('--deps', '-d', default='all',
+              type=click.Choice(['none', 'plan', 'run', 'build', 'all']),
+              help='The dependencies to show (default: all)')
+@click.option('--order', default="stage",
+              type=click.Choice(['stage', 'alpha']),
+              help='Staging or alphabetic ordering of dependencies')
+@click.option('--format', '-f', metavar='FORMAT', default=None,
+              type=click.STRING,
+              help='Format string for each element')
+@click.option('--downloadable', default=False, is_flag=True,
+              help="Refresh downloadable state")
+@click.argument('elements', nargs=-1,
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def show(app, elements, deps, except_, order, format, downloadable):
+    """Show elements in the pipeline
+
+    By default this will show all of the dependencies of the
+    specified target element.
+
+    Specify `--deps` to control which elements to show:
+
+    \b
+        none:  No dependencies, just the element itself
+        plan:  Dependencies required for a build plan
+        run:   Runtime dependencies, including the element itself
+        build: Build time dependencies, excluding the element itself
+        all:   All dependencies
+
+    \b
+    FORMAT
+    ~~~~~~
+    The --format option controls what should be printed for each element,
+    the following symbols can be used in the format string:
+
+    \b
+        %{name}           The element name
+        %{key}            The abbreviated cache key (if all sources are consistent)
+        %{full-key}       The full cache key (if all sources are consistent)
+        %{state}          cached, buildable, waiting or inconsistent
+        %{config}         The element configuration
+        %{vars}           Variable configuration
+        %{env}            Environment settings
+        %{public}         Public domain data
+        %{workspaced}     If the element is workspaced
+        %{workspace-dirs} A list of workspace directories
+
+    The value of the %{symbol} without the leading '%' character is understood
+    as a pythonic formatting string, so python formatting features apply,
+    examle:
+
+    \b
+        bst show target.bst --format \\
+            'Name: %{name: ^20} Key: %{key: ^8} State: %{state}'
+
+    If you want to use a newline in a format string in bash, use the '$' modifier:
+
+    \b
+        bst show target.bst --format \\
+            $'---------- %{name} ----------\\n%{vars}'
+    """
+    app.initialize(elements, except_=except_, use_configured_remote_caches=downloadable)
+    try:
+        dependencies = app.pipeline.deps_elements(deps)
+    except PipelineError as e:
+        click.echo("{}".format(e), err=True)
+        sys.exit(-1)
+
+    if order == "alpha":
+        dependencies = sorted(dependencies)
+
+    if not format:
+        format = app.context.log_element_format
+
+    report = app.logger.show_pipeline(dependencies, format)
+    click.echo(report, color=app.colors)
+
+
+##################################################################
+#                          Shell Command                         #
+##################################################################
+@cli.command(short_help="Shell into an element's sandbox environment")
+@click.option('--build', '-b', is_flag=True, default=False,
+              help='Create a build sandbox')
+@click.option('--sysroot', '-s', default=None,
+              type=click.Path(exists=True, file_okay=False, readable=True),
+              help="An existing sysroot")
+@click.argument('element',
+                type=click.Path(dir_okay=False, readable=True))
+@click.argument('command', type=click.STRING, nargs=-1)
+@click.pass_obj
+def shell(app, element, sysroot, build, command):
+    """Run a command in the target element's sandbox environment
+
+    This will first stage a temporary sysroot for running
+    the target element, assuming it has already been built
+    and all required artifacts are in the local cache.
+
+    Use the --build option to create a temporary sysroot for
+    building the element instead.
+
+    Use the --sysroot option with an existing failed build
+    directory or with a checkout of the given target, in order
+    to use a specific sysroot.
+
+    If no COMMAND is specified, the default is to attempt
+    to run an interactive shell with `sh -i`.
+    """
+    from ..element import Scope
+    if build:
+        scope = Scope.BUILD
+    else:
+        scope = Scope.RUN
+
+    app.initialize((element,))
+
+    # Assert we have everything we need built.
+    missing_deps = []
+    if scope is not None:
+        for dep in app.pipeline.dependencies(scope):
+            if not dep._cached():
+                missing_deps.append(dep)
+
+    if missing_deps:
+        click.echo("", err=True)
+        click.echo("Missing elements for staging an environment for a shell:", err=True)
+        for dep in missing_deps:
+            click.echo("   {}".format(dep.name), err=True)
+        click.echo("", err=True)
+        click.echo("Try building them first", err=True)
+        sys.exit(-1)
+
+    try:
+        exitcode = app.pipeline.targets[0]._shell(scope, sysroot, command=command)
+        sys.exit(exitcode)
+    except BstError as e:
+        click.echo("", err=True)
+        click.echo("Errors shelling into this pipeline: {}".format(e), err=True)
+        sys.exit(-1)
+
+
+##################################################################
+#                        Checkout Command                        #
+##################################################################
+@cli.command(short_help="Checkout a built artifact")
+@click.option('--force', '-f', default=False, is_flag=True,
+              help="Overwrite files existing in checkout directory")
+@click.option('--integrate/--no-integrate', default=True, is_flag=True,
+              help="Whether to run integration commands")
+@click.option('--hardlinks', default=False, is_flag=True,
+              help="Checkout hardlinks instead of copies (handle with care)")
+@click.argument('element',
+                type=click.Path(dir_okay=False, readable=True))
+@click.argument('directory', type=click.Path(file_okay=False))
+@click.pass_obj
+def checkout(app, element, directory, force, integrate, hardlinks):
+    """Checkout a built artifact to the specified directory
+    """
+    app.initialize((element,))
+    try:
+        app.pipeline.checkout(directory, force, integrate, hardlinks)
+        click.echo("", err=True)
+    except BstError as e:
+        app.print_error(e)
+        sys.exit(-1)
+
+
+##################################################################
+#                     Source Bundle Command                      #
+##################################################################
+@cli.command(name="source-bundle", short_help="Produce a build bundle to be manually executed")
+@click.option('--except', 'except_', multiple=True,
+              type=click.Path(dir_okay=False, readable=True),
+              help="Elements to except from the tarball")
+@click.option('--compression', default='gz',
+              type=click.Choice(['none', 'gz', 'bz2', 'xz']),
+              help="Compress the tar file using the given algorithm.")
+@click.option('--track', default=False, is_flag=True,
+              help="Track new source references before building")
+@click.option('--force', '-f', default=False, is_flag=True,
+              help="Overwrite files existing in checkout directory")
+@click.option('--directory', default=os.getcwd(),
+              help="The directory to write the tarball to")
+@click.argument('target',
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def source_bundle(app, target, force, directory,
+                  track, compression, except_):
+    """Produce a source bundle to be manually executed"""
+    app.initialize((target,), rewritable=track, track_elements=[target] if track else None)
+    try:
+        dependencies = app.pipeline.deps_elements('all')
+        app.print_heading(dependencies)
+        app.pipeline.source_bundle(app.scheduler, dependencies, force, track,
+                                   compression, directory)
+        click.echo("", err=True)
+    except BstError as e:
+        click.echo("", err=True)
+        click.echo("ERROR: {}".format(e), err=True)
+        sys.exit(-1)
+
+
+##################################################################
+#                      Workspace Command                         #
+##################################################################
+@cli.group(short_help="Manipulate developer workspaces")
+def workspace():
+    """Manipulate developer workspaces"""
+    pass
+
+
+##################################################################
+#                     Workspace Open Command                     #
+##################################################################
+@workspace.command(name='open', short_help="Open a new workspace")
+@click.option('--no-checkout', default=False, is_flag=True,
+              help="Do not checkout the source, only link to the given directory")
+@click.option('--force', '-f', default=False, is_flag=True,
+              help="Overwrite files existing in checkout directory")
+@click.option('--track', default=False, is_flag=True,
+              help="Track and fetch new source references before checking out the workspace")
+@click.argument('element',
+                type=click.Path(dir_okay=False, readable=True))
+@click.argument('directory', type=click.Path(file_okay=False))
+@click.pass_obj
+def workspace_open(app, no_checkout, force, track, element, directory):
+    """Open a workspace for manual source modification"""
+
+    app.initialize((element,), rewritable=track, track_elements=[element] if track else None)
+    try:
+        app.pipeline.open_workspace(app.scheduler, directory, no_checkout, track, force)
+        click.echo("", err=True)
+    except BstError as e:
+        click.echo("", err=True)
+        click.echo("ERROR: {}".format(e), err=True)
+        sys.exit(-1)
+
+
+##################################################################
+#                     Workspace Close Command                    #
+##################################################################
+@workspace.command(name='close', short_help="Close a workspace")
+@click.option('--remove-dir', default=False, is_flag=True,
+              help="Remove the path that contains the closed workspace")
+@click.argument('element',
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def workspace_close(app, remove_dir, element):
+    """Close a workspace"""
+
+    app.initialize((element,))
+    if app.interactive and remove_dir:
+        if not click.confirm('This will remove all your changes, are you sure?'):
+            click.echo('Aborting', err=True)
+            sys.exit(-1)
+
+    try:
+        app.pipeline.close_workspace(remove_dir)
+        click.echo("", err=True)
+    except BstError as e:
+        click.echo("", err=True)
+        click.echo("ERROR: {}".format(e), err=True)
+        sys.exit(-1)
+
+
+##################################################################
+#                     Workspace Reset Command                    #
+##################################################################
+@workspace.command(name='reset', short_help="Reset a workspace to its original state")
+@click.option('--track', default=False, is_flag=True,
+              help="Track and fetch the latest source before resetting")
+@click.option('--no-checkout', default=False, is_flag=True,
+              help="Do not checkout the source, only link to the given directory")
+@click.argument('element',
+                type=click.Path(dir_okay=False, readable=True))
+@click.pass_obj
+def workspace_reset(app, track, no_checkout, element):
+    """Reset a workspace to its original state"""
+    app.initialize((element,))
+    if app.interactive:
+        if not click.confirm('This will remove all your changes, are you sure?'):
+            click.echo('Aborting', err=True)
+            sys.exit(-1)
+
+    try:
+        app.pipeline.reset_workspace(app.scheduler, track, no_checkout)
+        click.echo("", err=True)
+    except BstError as e:
+        click.echo("", err=True)
+        click.echo("ERROR: {}".format(e), err=True)
+        sys.exit(-1)
+
+
+##################################################################
+#                     Workspace List Command                     #
+##################################################################
+@workspace.command(name='list', short_help="List open workspaces")
+@click.pass_obj
+def workspace_list(app):
+    """List open workspaces"""
+
+    from .. import _yaml
+    from .._context import Context
+    from .._project import Project
+
+    directory = app.main_options['directory']
+    config = app.main_options['config']
+
+    try:
+        context = Context()
+        context.load(config)
+    except BstError as e:
+        click.echo("Error loading user configuration: {}".format(e), err=True)
+        sys.exit(-1)
+
+    try:
+        project = Project(directory, context, cli_options=app.main_options['option'])
+    except BstError as e:
+        click.echo("Error loading project: {}".format(e), err=True)
+        sys.exit(-1)
+
+    workspaces = []
+    for element_name, directory in project._list_workspaces():
+        workspace = {
+            'element': element_name,
+            'directory': directory,
+        }
+
+        workspaces.append(workspace)
+
+    _yaml.dump({
+        'workspaces': workspaces
+    })
diff --git a/buildstream/_frontend/main.py b/buildstream/_frontend/main.py
index 18ca3d070..9cab22c4a 100644
--- a/buildstream/_frontend/main.py
+++ b/buildstream/_frontend/main.py
@@ -17,6 +17,8 @@
 #
 #  Authors:
 #        Tristan Van Berkom <tristan.vanberkom@codethink.co.uk>
+from .cli import cli
+
 import os
 import sys
 import click
@@ -48,693 +50,6 @@ INDENT = 4
 
 
 ##################################################################
-#            Override of click's main entry point                #
-##################################################################
-
-# Special completion for completing the bst elements in a project dir
-def complete_target(args, incomplete):
-    """
-    :param args: full list of args typed before the incomplete arg
-    :param incomplete: the incomplete text to autocomplete
-    :return: all the possible user-specified completions for the param
-    """
-
-    # First resolve the directory, in case there is an
-    # active --directory/-C option
-    #
-    base_directory = '.'
-    idx = -1
-    try:
-        idx = args.index('-C')
-    except ValueError:
-        try:
-            idx = args.index('--directory')
-        except ValueError:
-            pass
-
-    if idx >= 0 and len(args) > idx + 1:
-        base_directory = args[idx + 1]
-
-    # Now parse the project.conf just to find the element path,
-    # this is unfortunately a bit heavy.
-    project_file = os.path.join(base_directory, 'project.conf')
-    try:
-        project = _yaml.load(project_file)
-    except LoadError:
-        # If there is no project directory in context, just dont
-        # even bother trying to complete anything.
-        return []
-
-    # The project is not required to have an element-path
-    element_directory = project.get('element-path')
-
-    # If a project was loaded, use it's element-path to
-    # adjust our completion's base directory
-    if element_directory:
-        base_directory = os.path.join(base_directory, element_directory)
-
-    return complete_path("File", incomplete, base_directory=base_directory)
-
-
-def override_completions(cmd_param, args, incomplete):
-    """
-    :param cmd_param: command definition
-    :param args: full list of args typed before the incomplete arg
-    :param incomplete: the incomplete text to autocomplete
-    :return: all the possible user-specified completions for the param
-    """
-
-    # We can't easily extend click's data structures without
-    # modifying click itself, so just do some weak special casing
-    # right here and select which parameters we want to handle specially.
-    if isinstance(cmd_param.type, click.Path) and \
-       (cmd_param.name == 'elements' or
-        cmd_param.name == 'element' or
-        cmd_param.name == 'except_' or
-        cmd_param.opts == ['--track'] or
-        cmd_param.opts == ['--track-except']):
-        return complete_target(args, incomplete)
-
-    raise CompleteUnhandled()
-
-
-def override_main(self, args=None, prog_name=None, complete_var=None,
-                  standalone_mode=True, **extra):
-
-    # Hook for the Bash completion.  This only activates if the Bash
-    # completion is actually enabled, otherwise this is quite a fast
-    # noop.
-    if main_bashcomplete(self, prog_name, override_completions):
-
-        # If we're running tests we cant just go calling exit()
-        # from the main process.
-        #
-        # The below is a quicker exit path for the sake
-        # of making completions respond faster.
-        if 'BST_TEST_SUITE' not in os.environ:
-            sys.stdout.flush()
-            sys.stderr.flush()
-            os._exit(0)
-
-        # Regular client return for test cases
-        return
-
-    original_main(self, args=args, prog_name=prog_name, complete_var=None,
-                  standalone_mode=standalone_mode, **extra)
-
-
-original_main = click.BaseCommand.main
-click.BaseCommand.main = override_main
-
-
-##################################################################
-#                          Main Options                          #
-##################################################################
-@click.group(context_settings=dict(help_option_names=['-h', '--help']))
-@click.version_option(version=build_stream_version)
-@click.option('--config', '-c',
-              type=click.Path(exists=True, dir_okay=False, readable=True),
-              help="Configuration file to use")
-@click.option('--directory', '-C', default=os.getcwd(),
-              type=click.Path(exists=True, file_okay=False, readable=True),
-              help="Project directory (default: current directory)")
-@click.option('--on-error', default=None,
-              type=click.Choice(['continue', 'quit', 'terminate']),
-              help="What to do when an error is encountered")
-@click.option('--fetchers', type=click.INT, default=None,
-              help="Maximum simultaneous download tasks")
-@click.option('--builders', type=click.INT, default=None,
-              help="Maximum simultaneous build tasks")
-@click.option('--pushers', type=click.INT, default=None,
-              help="Maximum simultaneous upload tasks")
-@click.option('--network-retries', type=click.INT, default=None,
-              help="Maximum retries for network tasks")
-@click.option('--no-interactive', is_flag=True, default=False,
-              help="Force non interactive mode, otherwise this is automatically decided")
-@click.option('--verbose/--no-verbose', default=None,
-              help="Be extra verbose")
-@click.option('--debug/--no-debug', default=None,
-              help="Print debugging output")
-@click.option('--error-lines', type=click.INT, default=None,
-              help="Maximum number of lines to show from a task log")
-@click.option('--message-lines', type=click.INT, default=None,
-              help="Maximum number of lines to show in a detailed message")
-@click.option('--log-file',
-              type=click.File(mode='w', encoding='UTF-8'),
-              help="A file to store the main log (allows storing the main log while in interactive mode)")
-@click.option('--colors/--no-colors', default=None,
-              help="Force enable/disable ANSI color codes in output")
-@click.option('--strict/--no-strict', default=None, is_flag=True,
-              help="Elements must be rebuilt when their dependencies have changed")
-@click.option('--option', '-o', type=click.Tuple([str, str]), multiple=True,
-              help="Specify a project option")
-@click.pass_context
-def cli(context, **kwargs):
-    """Build and manipulate BuildStream projects
-
-    Most of the main options override options in the
-    user preferences configuration file.
-    """
-
-    # Create the App, giving it the main arguments
-    context.obj = App(dict(kwargs))
-    context.call_on_close(context.obj.cleanup)
-
-
-##################################################################
-#                          Build Command                         #
-##################################################################
-@cli.command(short_help="Build elements in a pipeline")
-@click.option('--all', default=False, is_flag=True,
-              help="Build elements that would not be needed for the current build plan")
-@click.option('--track', multiple=True,
-              type=click.Path(dir_okay=False, readable=True),
-              help="Specify elements to track during the build. Can be used "
-                   "repeatedly to specify multiple elements")
-@click.option('--track-all', default=False, is_flag=True,
-              help="Track all elements in the pipeline")
-@click.option('--track-except', multiple=True,
-              type=click.Path(dir_okay=False, readable=True),
-              help="Except certain dependencies from tracking")
-@click.option('--track-save', default=False, is_flag=True,
-              help="Write out the tracked references to their element files")
-@click.argument('elements', nargs=-1,
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def build(app, elements, all, track, track_save, track_all, track_except):
-    """Build elements in a pipeline"""
-
-    if track_all:
-        track = elements
-
-    app.initialize(elements, except_=track_except, rewritable=track_save,
-                   use_configured_remote_caches=True, track_elements=track,
-                   fetch_subprojects=True)
-    app.print_heading()
-    try:
-        app.pipeline.build(app.scheduler, all, track, track_save)
-        app.print_summary()
-    except PipelineError as e:
-        app.print_error(e)
-        app.print_summary()
-        sys.exit(-1)
-
-
-##################################################################
-#                          Fetch Command                         #
-##################################################################
-@cli.command(short_help="Fetch sources in a pipeline")
-@click.option('--except', 'except_', multiple=True,
-              type=click.Path(dir_okay=False, readable=True),
-              help="Except certain dependencies from fetching")
-@click.option('--deps', '-d', default='plan',
-              type=click.Choice(['none', 'plan', 'all']),
-              help='The dependencies to fetch (default: plan)')
-@click.option('--track', default=False, is_flag=True,
-              help="Track new source references before fetching")
-@click.argument('elements', nargs=-1,
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def fetch(app, elements, deps, track, except_):
-    """Fetch sources required to build the pipeline
-
-    By default this will only try to fetch sources which are
-    required for the build plan of the specified target element,
-    omitting sources for any elements which are already built
-    and available in the artifact cache.
-
-    Specify `--deps` to control which sources to fetch:
-
-    \b
-        none:  No dependencies, just the element itself
-        plan:  Only dependencies required for the build plan
-        all:   All dependencies
-    """
-
-    app.initialize(elements, except_=except_, rewritable=track,
-                   track_elements=elements if track else None,
-                   fetch_subprojects=True)
-    try:
-        dependencies = app.pipeline.deps_elements(deps)
-        app.print_heading(deps=dependencies)
-        app.pipeline.fetch(app.scheduler, dependencies, track)
-        app.print_summary()
-    except PipelineError as e:
-        app.print_error(e)
-        app.print_summary()
-        sys.exit(-1)
-
-
-##################################################################
-#                          Track Command                         #
-##################################################################
-@cli.command(short_help="Track new source references")
-@click.option('--except', 'except_', multiple=True,
-              type=click.Path(dir_okay=False, readable=True),
-              help="Except certain dependencies from tracking")
-@click.option('--deps', '-d', default='none',
-              type=click.Choice(['none', 'all']),
-              help='The dependencies to track (default: none)')
-@click.argument('elements', nargs=-1,
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def track(app, elements, deps, except_):
-    """Consults the specified tracking branches for new versions available
-    to build and updates the project with any newly available references.
-
-    By default this will track just the specified element, but you can also
-    update a whole tree of dependencies in one go.
-
-    Specify `--deps` to control which sources to track:
-
-    \b
-        none:  No dependencies, just the element itself
-        all:   All dependencies
-    """
-    app.initialize(elements, except_=except_, rewritable=True, track_elements=elements,
-                   fetch_subprojects=True)
-    try:
-        dependencies = app.pipeline.deps_elements(deps)
-        app.print_heading(deps=dependencies)
-        app.pipeline.track(app.scheduler, dependencies)
-        app.print_summary()
-    except PipelineError as e:
-        app.print_error(e)
-        app.print_summary()
-        sys.exit(-1)
-
-
-##################################################################
-#                           Pull Command                         #
-##################################################################
-@cli.command(short_help="Pull a built artifact")
-@click.option('--deps', '-d', default='none',
-              type=click.Choice(['none', 'all']),
-              help='The dependency artifacts to pull (default: none)')
-@click.option('--remote', '-r',
-              help="The URL of the remote cache (defaults to the first configured cache)")
-@click.argument('elements', nargs=-1,
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def pull(app, elements, deps, remote):
-    """Pull a built artifact from the configured remote artifact cache.
-
-    By default the artifact will be pulled one of the configured caches
-    if possible, following the usual priority order. If the `--remote` flag
-    is given, only the specified cache will be queried.
-
-    Specify `--deps` to control which artifacts to pull:
-
-    \b
-        none:  No dependencies, just the element itself
-        all:   All dependencies
-    """
-    app.initialize(elements, use_configured_remote_caches=(remote is None),
-                   add_remote_cache=remote, fetch_subprojects=True)
-    try:
-        to_pull = app.pipeline.deps_elements(deps)
-        app.pipeline.pull(app.scheduler, to_pull)
-        app.print_summary()
-    except BstError as e:
-        app.print_error(e)
-        app.print_summary()
-        sys.exit(-1)
-
-
-##################################################################
-#                           Push Command                         #
-##################################################################
-@cli.command(short_help="Push a built artifact")
-@click.option('--deps', '-d', default='none',
-              type=click.Choice(['none', 'all']),
-              help='The dependencies to push (default: none)')
-@click.option('--remote', '-r', default=None,
-              help="The URL of the remote cache (defaults to the first configured cache)")
-@click.argument('elements', nargs=-1,
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def push(app, elements, deps, remote):
-    """Push a built artifact to a remote artifact cache.
-
-    The default destination is the highest priority configured cache. You can
-    override this by passing a different cache URL with the `--remote` flag.
-
-    Specify `--deps` to control which artifacts to push:
-
-    \b
-        none:  No dependencies, just the element itself
-        all:   All dependencies
-    """
-    app.initialize(elements, use_configured_remote_caches=(remote is None),
-                   add_remote_cache=remote, fetch_subprojects=True)
-    try:
-        to_push = app.pipeline.deps_elements(deps)
-        app.pipeline.push(app.scheduler, to_push)
-        app.print_summary()
-    except BstError as e:
-        app.print_error(e)
-        app.print_summary()
-        sys.exit(-1)
-
-
-##################################################################
-#                           Show Command                         #
-##################################################################
-@cli.command(short_help="Show elements in the pipeline")
-@click.option('--except', 'except_', multiple=True,
-              type=click.Path(dir_okay=False, readable=True),
-              help="Except certain dependencies")
-@click.option('--deps', '-d', default='all',
-              type=click.Choice(['none', 'plan', 'run', 'build', 'all']),
-              help='The dependencies to show (default: all)')
-@click.option('--order', default="stage",
-              type=click.Choice(['stage', 'alpha']),
-              help='Staging or alphabetic ordering of dependencies')
-@click.option('--format', '-f', metavar='FORMAT', default=None,
-              type=click.STRING,
-              help='Format string for each element')
-@click.option('--downloadable', default=False, is_flag=True,
-              help="Refresh downloadable state")
-@click.argument('elements', nargs=-1,
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def show(app, elements, deps, except_, order, format, downloadable):
-    """Show elements in the pipeline
-
-    By default this will show all of the dependencies of the
-    specified target element.
-
-    Specify `--deps` to control which elements to show:
-
-    \b
-        none:  No dependencies, just the element itself
-        plan:  Dependencies required for a build plan
-        run:   Runtime dependencies, including the element itself
-        build: Build time dependencies, excluding the element itself
-        all:   All dependencies
-
-    \b
-    FORMAT
-    ~~~~~~
-    The --format option controls what should be printed for each element,
-    the following symbols can be used in the format string:
-
-    \b
-        %{name}           The element name
-        %{key}            The abbreviated cache key (if all sources are consistent)
-        %{full-key}       The full cache key (if all sources are consistent)
-        %{state}          cached, buildable, waiting or inconsistent
-        %{config}         The element configuration
-        %{vars}           Variable configuration
-        %{env}            Environment settings
-        %{public}         Public domain data
-        %{workspaced}     If the element is workspaced
-        %{workspace-dirs} A list of workspace directories
-
-    The value of the %{symbol} without the leading '%' character is understood
-    as a pythonic formatting string, so python formatting features apply,
-    examle:
-
-    \b
-        bst show target.bst --format \\
-            'Name: %{name: ^20} Key: %{key: ^8} State: %{state}'
-
-    If you want to use a newline in a format string in bash, use the '$' modifier:
-
-    \b
-        bst show target.bst --format \\
-            $'---------- %{name} ----------\\n%{vars}'
-    """
-    app.initialize(elements, except_=except_, use_configured_remote_caches=downloadable)
-    try:
-        dependencies = app.pipeline.deps_elements(deps)
-    except PipelineError as e:
-        click.echo("{}".format(e), err=True)
-        sys.exit(-1)
-
-    if order == "alpha":
-        dependencies = sorted(dependencies)
-
-    if not format:
-        format = app.context.log_element_format
-
-    report = app.logger.show_pipeline(dependencies, format)
-    click.echo(report, color=app.colors)
-
-
-##################################################################
-#                          Shell Command                         #
-##################################################################
-@cli.command(short_help="Shell into an element's sandbox environment")
-@click.option('--build', '-b', is_flag=True, default=False,
-              help='Create a build sandbox')
-@click.option('--sysroot', '-s', default=None,
-              type=click.Path(exists=True, file_okay=False, readable=True),
-              help="An existing sysroot")
-@click.argument('element',
-                type=click.Path(dir_okay=False, readable=True))
-@click.argument('command', type=click.STRING, nargs=-1)
-@click.pass_obj
-def shell(app, element, sysroot, build, command):
-    """Run a command in the target element's sandbox environment
-
-    This will first stage a temporary sysroot for running
-    the target element, assuming it has already been built
-    and all required artifacts are in the local cache.
-
-    Use the --build option to create a temporary sysroot for
-    building the element instead.
-
-    Use the --sysroot option with an existing failed build
-    directory or with a checkout of the given target, in order
-    to use a specific sysroot.
-
-    If no COMMAND is specified, the default is to attempt
-    to run an interactive shell with `sh -i`.
-    """
-    if build:
-        scope = Scope.BUILD
-    else:
-        scope = Scope.RUN
-
-    app.initialize((element,))
-
-    # Assert we have everything we need built.
-    missing_deps = []
-    if scope is not None:
-        for dep in app.pipeline.dependencies(scope):
-            if not dep._cached():
-                missing_deps.append(dep)
-
-    if missing_deps:
-        click.echo("", err=True)
-        click.echo("Missing elements for staging an environment for a shell:", err=True)
-        for dep in missing_deps:
-            click.echo("   {}".format(dep.name), err=True)
-        click.echo("", err=True)
-        click.echo("Try building them first", err=True)
-        sys.exit(-1)
-
-    try:
-        exitcode = app.pipeline.targets[0]._shell(scope, sysroot, command=command)
-        sys.exit(exitcode)
-    except BstError as e:
-        click.echo("", err=True)
-        click.echo("Errors shelling into this pipeline: {}".format(e), err=True)
-        sys.exit(-1)
-
-
-##################################################################
-#                        Checkout Command                        #
-##################################################################
-@cli.command(short_help="Checkout a built artifact")
-@click.option('--force', '-f', default=False, is_flag=True,
-              help="Overwrite files existing in checkout directory")
-@click.option('--integrate/--no-integrate', default=True, is_flag=True,
-              help="Whether to run integration commands")
-@click.option('--hardlinks', default=False, is_flag=True,
-              help="Checkout hardlinks instead of copies (handle with care)")
-@click.argument('element',
-                type=click.Path(dir_okay=False, readable=True))
-@click.argument('directory', type=click.Path(file_okay=False))
-@click.pass_obj
-def checkout(app, element, directory, force, integrate, hardlinks):
-    """Checkout a built artifact to the specified directory
-    """
-    app.initialize((element,))
-    try:
-        app.pipeline.checkout(directory, force, integrate, hardlinks)
-        click.echo("", err=True)
-    except BstError as e:
-        app.print_error(e)
-        sys.exit(-1)
-
-
-##################################################################
-#                     Source Bundle Command                      #
-##################################################################
-@cli.command(name="source-bundle", short_help="Produce a build bundle to be manually executed")
-@click.option('--except', 'except_', multiple=True,
-              type=click.Path(dir_okay=False, readable=True),
-              help="Elements to except from the tarball")
-@click.option('--compression', default='gz',
-              type=click.Choice(['none', 'gz', 'bz2', 'xz']),
-              help="Compress the tar file using the given algorithm.")
-@click.option('--track', default=False, is_flag=True,
-              help="Track new source references before building")
-@click.option('--force', '-f', default=False, is_flag=True,
-              help="Overwrite files existing in checkout directory")
-@click.option('--directory', default=os.getcwd(),
-              help="The directory to write the tarball to")
-@click.argument('target',
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def source_bundle(app, target, force, directory,
-                  track, compression, except_):
-    """Produce a source bundle to be manually executed"""
-    app.initialize((target,), rewritable=track, track_elements=[target] if track else None)
-    try:
-        dependencies = app.pipeline.deps_elements('all')
-        app.print_heading(dependencies)
-        app.pipeline.source_bundle(app.scheduler, dependencies, force, track,
-                                   compression, directory)
-        click.echo("", err=True)
-    except BstError as e:
-        click.echo("", err=True)
-        click.echo("ERROR: {}".format(e), err=True)
-        sys.exit(-1)
-
-
-##################################################################
-#                      Workspace Command                         #
-##################################################################
-@cli.group(short_help="Manipulate developer workspaces")
-def workspace():
-    """Manipulate developer workspaces"""
-    pass
-
-
-##################################################################
-#                     Workspace Open Command                     #
-##################################################################
-@workspace.command(name='open', short_help="Open a new workspace")
-@click.option('--no-checkout', default=False, is_flag=True,
-              help="Do not checkout the source, only link to the given directory")
-@click.option('--force', '-f', default=False, is_flag=True,
-              help="Overwrite files existing in checkout directory")
-@click.option('--track', default=False, is_flag=True,
-              help="Track and fetch new source references before checking out the workspace")
-@click.argument('element',
-                type=click.Path(dir_okay=False, readable=True))
-@click.argument('directory', type=click.Path(file_okay=False))
-@click.pass_obj
-def workspace_open(app, no_checkout, force, track, element, directory):
-    """Open a workspace for manual source modification"""
-
-    app.initialize((element,), rewritable=track, track_elements=[element] if track else None)
-    try:
-        app.pipeline.open_workspace(app.scheduler, directory, no_checkout, track, force)
-        click.echo("", err=True)
-    except BstError as e:
-        click.echo("", err=True)
-        click.echo("ERROR: {}".format(e), err=True)
-        sys.exit(-1)
-
-
-##################################################################
-#                     Workspace Close Command                    #
-##################################################################
-@workspace.command(name='close', short_help="Close a workspace")
-@click.option('--remove-dir', default=False, is_flag=True,
-              help="Remove the path that contains the closed workspace")
-@click.argument('element',
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def workspace_close(app, remove_dir, element):
-    """Close a workspace"""
-
-    app.initialize((element,))
-    if app.interactive and remove_dir:
-        if not click.confirm('This will remove all your changes, are you sure?'):
-            click.echo('Aborting', err=True)
-            sys.exit(-1)
-
-    try:
-        app.pipeline.close_workspace(remove_dir)
-        click.echo("", err=True)
-    except BstError as e:
-        click.echo("", err=True)
-        click.echo("ERROR: {}".format(e), err=True)
-        sys.exit(-1)
-
-
-##################################################################
-#                     Workspace Reset Command                    #
-##################################################################
-@workspace.command(name='reset', short_help="Reset a workspace to its original state")
-@click.option('--track', default=False, is_flag=True,
-              help="Track and fetch the latest source before resetting")
-@click.option('--no-checkout', default=False, is_flag=True,
-              help="Do not checkout the source, only link to the given directory")
-@click.argument('element',
-                type=click.Path(dir_okay=False, readable=True))
-@click.pass_obj
-def workspace_reset(app, track, no_checkout, element):
-    """Reset a workspace to its original state"""
-    app.initialize((element,))
-    if app.interactive:
-        if not click.confirm('This will remove all your changes, are you sure?'):
-            click.echo('Aborting', err=True)
-            sys.exit(-1)
-
-    try:
-        app.pipeline.reset_workspace(app.scheduler, track, no_checkout)
-        click.echo("", err=True)
-    except BstError as e:
-        click.echo("", err=True)
-        click.echo("ERROR: {}".format(e), err=True)
-        sys.exit(-1)
-
-
-##################################################################
-#                     Workspace List Command                     #
-##################################################################
-@workspace.command(name='list', short_help="List open workspaces")
-@click.pass_obj
-def workspace_list(app):
-    """List open workspaces"""
-
-    directory = app.main_options['directory']
-    config = app.main_options['config']
-
-    try:
-        context = Context()
-        context.load(config)
-    except BstError as e:
-        click.echo("Error loading user configuration: {}".format(e), err=True)
-        sys.exit(-1)
-
-    try:
-        project = Project(directory, context, cli_options=app.main_options['option'])
-    except BstError as e:
-        click.echo("Error loading project: {}".format(e), err=True)
-        sys.exit(-1)
-
-    workspaces = []
-    for element_name, directory in project._list_workspaces():
-        workspace = {
-            'element': element_name,
-            'directory': directory,
-        }
-
-        workspaces.append(workspace)
-
-    _yaml.dump({
-        'workspaces': workspaces
-    })
-
-
-##################################################################
 #                    Main Application State                      #
 ##################################################################
 
diff --git a/buildstream/_yaml.py b/buildstream/_yaml.py
index 7bb9b7867..0e85f0bfa 100644
--- a/buildstream/_yaml.py
+++ b/buildstream/_yaml.py
@@ -26,7 +26,6 @@ from contextlib import ExitStack
 from ruamel import yaml
 from ruamel.yaml.representer import SafeRepresenter, RoundTripRepresenter
 from ._exceptions import LoadError, LoadErrorReason
-from . import utils
 
 
 # We store information in the loaded yaml on a DictProvenance
@@ -214,6 +213,7 @@ def load_data(data, shortname=None, copy_tree=False):
 def dump(node, filename=None):
     with ExitStack() as stack:
         if filename:
+            from . import utils
             f = stack.enter_context(utils.save_file_atomic(filename, 'w'))
         else:
             f = sys.stdout