_stream.py: Add query_cache() method

This is preparation for explicit cache query.

2 files changed, 20 insertions, 0 deletions

diff --git a/src/buildstream/_frontend/cli.py b/src/buildstream/_frontend/cli.py
index 5e42bda68..3428b3d27 100644
--- a/src/buildstream/_frontend/cli.py
+++ b/src/buildstream/_frontend/cli.py
@@ -551,6 +551,8 @@ def show(app, elements, deps, except_, order, format_):
 
         dependencies = app.stream.load_selection(elements, selection=deps, except_targets=except_)
 
+        app.stream.query_cache(dependencies)
+
         if order == "alpha":
             dependencies = sorted(dependencies)
 
diff --git a/src/buildstream/_stream.py b/src/buildstream/_stream.py
index 91d7cb122..0d2ddfbc3 100644
--- a/src/buildstream/_stream.py
+++ b/src/buildstream/_stream.py
@@ -162,6 +162,18 @@ class Stream:
 
             return target_objects
 
+    # query_cache()
+    #
+    # Query the artifact and source caches to determine the cache status
+    # of the specified elements.
+    #
+    # Args:
+    #    elements (list of Element): The elements to check
+    #
+    def query_cache(self, elements):
+        # Cache is implicitly queried on demand
+        pass
+
     # shell()
     #
     # Run a shell
@@ -613,6 +625,8 @@ class Stream:
             targets, selection=selection, use_artifact_config=True, load_artifacts=True
         )
 
+        self.query_cache(target_objects)
+
         if self._artifacts.has_fetch_remotes():
             self._pipeline.check_remotes(target_objects)
 
@@ -638,6 +652,8 @@ class Stream:
         # Return list of Element and/or ArtifactElement objects
         target_objects = self.load_selection(targets, selection=_PipelineSelection.NONE, load_artifacts=True)
 
+        self.query_cache(target_objects)
+
         artifact_logs = {}
         for obj in target_objects:
             ref = obj.get_artifact_name()
@@ -666,6 +682,8 @@ class Stream:
         # Return list of Element and/or ArtifactElement objects
         target_objects = self.load_selection(targets, selection=_PipelineSelection.NONE, load_artifacts=True)
 
+        self.query_cache(target_objects)
+
         elements_to_files = {}
         for obj in target_objects:
             ref = obj.get_artifact_name()