Add initial `bst pull` command

3 files changed, 71 insertions, 1 deletions

diff --git a/buildstream/_frontend/main.py b/buildstream/_frontend/main.py
index aaf625e01..ab3c81501 100644
--- a/buildstream/_frontend/main.py
+++ b/buildstream/_frontend/main.py
@@ -209,6 +209,37 @@ def track(app, target, variant, deps, except_):
 
 
 ##################################################################
+#                           Pull Command                         #
+##################################################################
+@cli.command(short_help="Pull a built artifact")
+@click.option('--variant',
+              help='A variant of the specified target')
+@click.option('--deps', '-d', default='none',
+              type=click.Choice(['none', 'all']),
+              help='The dependencies to fetch (default: plan)')
+@click.argument('target')
+@click.pass_obj
+def pull(app, target, variant, deps):
+    """Pull a built artifact from the configured remote artifact cache.
+
+    Specify `--deps` to control which artifacts to pull:
+
+    \b
+        none:  No dependencies, just the element itself
+        all:   All dependencies
+    """
+    app.initialize(target, variant)
+    try:
+        to_pull = app.pipeline.deps_elements(deps)
+        app.pipeline.pull(app.scheduler, to_pull)
+        click.echo("")
+    except _BstError as e:
+        click.echo("")
+        click.echo("ERROR: {}".format(e))
+        sys.exit(-1)
+
+
+##################################################################
 #                           Push Command                         #
 ##################################################################
 @cli.command(short_help="Push a built artifact")
diff --git a/buildstream/_pipeline.py b/buildstream/_pipeline.py
index dc71afa1f..1e2ffcb03 100644
--- a/buildstream/_pipeline.py
+++ b/buildstream/_pipeline.py
@@ -630,6 +630,44 @@ class Pipeline():
 
         self.open_workspace(scheduler, workspace_dir, source_index, no_checkout,
                             track, False)
+    # pull()
+    #
+    # Pulls elements from the pipeline
+    #
+    # Args:
+    #    scheduler (Scheduler): The scheduler to run this pipeline on
+    #    elements (list): List of elements to pull
+    #
+    def pull(self, scheduler, elements):
+
+        if not self.artifacts.can_fetch():
+            self.message(self.target, MessageType.FAIL, "Not configured for pulling artifacts")
+
+        plan = elements
+        self.assert_consistent(plan)
+        self.session_elements = len(plan)
+
+        pull = PullQueue()
+        pull.enqueue(plan)
+        queues = [pull]
+
+        self.message(self.target, MessageType.START, "Pulling {} artifacts".format(len(plan)))
+        elapsed, status = scheduler.run(queues)
+        pulled = len(pull.processed_elements)
+
+        if status == SchedStatus.ERROR:
+            self.message(self.target, MessageType.FAIL, "Pull failed", elapsed=elapsed)
+            raise PipelineError()
+        elif status == SchedStatus.TERMINATED:
+            self.message(self.target, MessageType.WARN,
+                         "Terminated after pulling {} elements".format(pulled),
+                         elapsed=elapsed)
+            raise PipelineError()
+        else:
+            self.message(self.target, MessageType.SUCCESS,
+                         "Pulled {} complete".format(pulled),
+                         elapsed=elapsed)
+
     # push()
     #
     # Pushes elements in the pipeline
diff --git a/buildstream/element.py b/buildstream/element.py
index 84cd9a577..09ead8264 100644
--- a/buildstream/element.py
+++ b/buildstream/element.py
@@ -1149,7 +1149,8 @@ class Element(Plugin):
     #   (bool): True if this element should not be pushed
     #
     def _skip_push(self):
-        self._assert_cached()
+        if not self._cached(recalculate=None):
+            return True
 
         # Do not push tained artifact
         if self._tainted():