_pipeline.py: Added PipelineSelection

Part of a slow, ongoing refactor to unmangle the pipeline into
something which just creates pipelines of elements for a centerpiece
to process.

This also renames Pipeline.deps_elements() -> Pipeline.get_selection()

2 files changed, 41 insertions, 14 deletions

diff --git a/buildstream/_frontend/cli.py b/buildstream/_frontend/cli.py
index 3d50d5c14..213c4ed1e 100644
--- a/buildstream/_frontend/cli.py
+++ b/buildstream/_frontend/cli.py
@@ -277,7 +277,7 @@ def fetch(app, elements, deps, track_, except_, track_cross_junctions):
                          track_elements=elements if track_ else None,
                          track_cross_junctions=track_cross_junctions,
                          fetch_subprojects=True):
-        dependencies = app.pipeline.deps_elements(deps)
+        dependencies = app.pipeline.get_selection(deps)
         app.pipeline.fetch(app.scheduler, dependencies)
 
 
@@ -313,7 +313,7 @@ def track(app, elements, deps, except_, cross_junctions):
                          track_elements=elements,
                          track_cross_junctions=cross_junctions,
                          fetch_subprojects=True):
-        dependencies = app.pipeline.deps_elements(deps)
+        dependencies = app.pipeline.get_selection(deps)
         app.pipeline.track(app.scheduler)
 
 
@@ -344,7 +344,7 @@ def pull(app, elements, deps, remote):
     """
     with app.initialized(elements, session_name="Pull", use_configured_remote_caches=(remote is None),
                          add_remote_cache=remote, fetch_subprojects=True):
-        to_pull = app.pipeline.deps_elements(deps)
+        to_pull = app.pipeline.get_selection(deps)
         app.pipeline.pull(app.scheduler, to_pull)
 
 
@@ -375,7 +375,7 @@ def push(app, elements, deps, remote):
     with app.initialized(elements, session_name="Push",
                          use_configured_remote_caches=(remote is None),
                          add_remote_cache=remote, fetch_subprojects=True):
-        to_push = app.pipeline.deps_elements(deps)
+        to_push = app.pipeline.get_selection(deps)
         app.pipeline.push(app.scheduler, to_push)
 
 
@@ -449,7 +449,7 @@ def show(app, elements, deps, except_, order, format_, downloadable):
     """
     with app.initialized(elements, except_=except_, use_configured_remote_caches=downloadable):
 
-        dependencies = app.pipeline.deps_elements(deps)
+        dependencies = app.pipeline.get_selection(deps)
         if order == "alpha":
             dependencies = sorted(dependencies)
 
@@ -582,7 +582,7 @@ def source_bundle(app, target, force, directory,
     """Produce a source bundle to be manually executed
     """
     with app.initialized((target,), rewritable=track_, track_elements=[target] if track_ else None):
-        dependencies = app.pipeline.deps_elements('all')
+        dependencies = app.pipeline.get_selection('all')
         app.pipeline.source_bundle(app.scheduler, dependencies, force, track_,
                                    compression, directory)
 
diff --git a/buildstream/_pipeline.py b/buildstream/_pipeline.py
index e4e8377c2..540d0715f 100644
--- a/buildstream/_pipeline.py
+++ b/buildstream/_pipeline.py
@@ -42,6 +42,33 @@ from ._artifactcache.artifactcache import ArtifactCacheSpec, configured_remote_a
 from ._scheduler import SchedStatus, TrackQueue, FetchQueue, BuildQueue, PullQueue, PushQueue
 
 
+# PipelineSelection()
+#
+# Defines the kind of pipeline selection to make when the pipeline
+# is provided a list of targets, for whichever purpose.
+#
+# These values correspond to the CLI `--deps` arguments for convenience.
+#
+class PipelineSelection():
+
+    # Select only the target elements in the associated targets
+    NONE = 'none'
+
+    # Select elements which must be built for the associated targets to be built
+    PLAN = 'plan'
+
+    # All dependencies of all targets, including the targets
+    ALL = 'all'
+
+    # All direct build dependencies and their recursive runtime dependencies,
+    # excluding the targets
+    BUILD = 'build'
+
+    # All direct runtime dependencies and their recursive runtime dependencies,
+    # including the targets
+    RUN = 'run'
+
+
 # Pipeline()
 #
 # Args:
@@ -176,28 +203,28 @@ class Pipeline():
         # Reset the element loader state
         Element._reset_load_state()
 
-    # deps_elements()
+    # get_selection()
     #
     # Args:
-    #    mode (str): A specific mode of resolving deps
+    #    mode (PipelineSelection): The PipelineSelection mode
     #
     # Various commands define a --deps option to specify what elements to
     # use in the result, this function reports a list that is appropriate for
     # the selected option.
     #
-    def deps_elements(self, mode):
+    def get_selection(self, mode):
 
         elements = None
-        if mode == 'none':
+        if mode == PipelineSelection.NONE:
             elements = self.targets
-        elif mode == 'plan':
+        elif mode == PipelineSelection.PLAN:
             elements = list(self._plan())
         else:
-            if mode == 'all':
+            if mode == PipelineSelection.ALL:
                 scope = Scope.ALL
-            elif mode == 'build':
+            elif mode == PipelineSelection.BUILD:
                 scope = Scope.BUILD
-            elif mode == 'run':
+            elif mode == PipelineSelection.RUN:
                 scope = Scope.RUN
 
             elements = list(self.dependencies(scope))