cli.py/_stream.py: Add pull option to checkout

This will set up a pull queue and pull relevant artifacts if not present
or incomplete.

Part of #1044

2 files changed, 24 insertions, 6 deletions

diff --git a/src/buildstream/_frontend/cli.py b/src/buildstream/_frontend/cli.py
index 2301fcb78..b353ced93 100644
--- a/src/buildstream/_frontend/cli.py
+++ b/src/buildstream/_frontend/cli.py
@@ -950,13 +950,16 @@ def artifact():
               help="Create a tarball from the artifact contents instead "
                    "of a file tree. If LOCATION is '-', the tarball "
                    "will be dumped to the standard output.")
+@click.option('--pull', 'pull_', default=False, is_flag=True,
+              help="Whether to pull the artifact if it's missing or "
+                   "incomplete.")
 @click.option('--directory', default=None,
               type=click.Path(file_okay=False),
               help="The directory to checkout the artifact to")
 @click.argument('element', required=False,
                 type=click.Path(readable=False))
 @click.pass_obj
-def artifact_checkout(app, force, deps, integrate, hardlinks, tar, directory, element):
+def artifact_checkout(app, force, deps, integrate, hardlinks, tar, pull_, directory, element):
     """Checkout contents of an artifact
 
     When this command is executed from a workspace directory, the default
@@ -1002,7 +1005,8 @@ def artifact_checkout(app, force, deps, integrate, hardlinks, tar, directory, el
                             scope=scope,
                             integrate=True if integrate is None else integrate,
                             hardlinks=hardlinks,
-                            tar=tar)
+                            tar=tar,
+                            pull=pull_)
 
 
 ################################################################
diff --git a/src/buildstream/_stream.py b/src/buildstream/_stream.py
index 0606c906a..6f6d30f17 100644
--- a/src/buildstream/_stream.py
+++ b/src/buildstream/_stream.py
@@ -474,6 +474,8 @@ class Stream():
     #                will be placed at the given location. If true and
     #                location is '-', the tarball will be dumped on the
     #                standard output.
+    #    pull (bool): If true will attempt to pull any missing or incomplete
+    #                 artifacts.
     #
     def checkout(self, target, *,
                  location=None,
@@ -481,14 +483,26 @@ class Stream():
                  scope=Scope.RUN,
                  integrate=True,
                  hardlinks=False,
-                 tar=False):
+                 tar=False,
+                 pull=False):
 
-        # We only have one target in a checkout command
-        elements, _ = self._load((target,), (), fetch_subprojects=True)
-        target = elements[0]
+        # if pulling we need to ensure dependency artifacts are also pulled
+        selection = PipelineSelection.RUN if pull else PipelineSelection.NONE
+        elements, _ = self._load(
+            (target,), (), selection=selection,
+            fetch_subprojects=True, use_artifact_config=True)
+
+        target = elements[-1]
 
         self._check_location_writable(location, force=force, tar=tar)
 
+        uncached_elts = [elt for elt in elements if not elt._cached()]
+        if uncached_elts and pull:
+            self._message(MessageType.INFO, "Attempting to fetch missing or incomplete artifact")
+            self._add_queue(PullQueue(self._scheduler))
+            self._enqueue_plan(uncached_elts)
+            self._run()
+
         # Stage deps into a temporary sandbox first
         try:
             with target._prepare_sandbox(scope=scope, directory=None,