_stream: Don't require runtime deps when building with --deps none

doc/source/using_config.rst

@@ -381,6 +381,7 @@ Attributes
   values for this attribute are:
 
   * ``none``: Only build elements required to generate the expected target artifacts
+  * ``run``: Build required elements and their their runtime dependencies
   * ``all``: Build elements even if they are build dependencies of artifacts which are already cached
 
 

src/buildstream/_context.py

@@ -465,10 +465,10 @@ def load(self, config: Optional[str] = None) -> None:
         self.build_retry_failed = build.get_bool("retry-failed")
 
         dependencies = build.get_str("dependencies")
-        if dependencies not in ["none", "all"]:
+        if dependencies not in ["none", "run", "all"]:
             provenance = build.get_scalar("dependencies").get_provenance()
             raise LoadError(
-                "{}: Invalid value for 'dependencies'. Choose 'none' or 'all'.".format(provenance),
+                "{}: Invalid value for 'dependencies'. Choose 'none', 'run', or 'all'.".format(provenance),
                 LoadErrorReason.INVALID_DATA,
             )
         self.build_dependencies = _PipelineSelection(dependencies)

src/buildstream/_frontend/cli.py

@@ -455,7 +455,7 @@ def init(app, project_name, min_version, element_path, force, target_directory):
     default=None,
     type=FastEnumType(
         _PipelineSelection,
-        [_PipelineSelection.NONE, _PipelineSelection.BUILD, _PipelineSelection.ALL],
+        [_PipelineSelection.NONE, _PipelineSelection.BUILD, _PipelineSelection.RUN, _PipelineSelection.ALL],
     ),
     help="The dependencies to build",
 )
@@ -513,6 +513,7 @@ def build(
     \b
         none:  No dependencies, just the element itself
         build: Build time dependencies, excluding the element itself
+        run:   The element and its runtime dependencies
         all:   All dependencies
 
     Dependencies that are consequently required to build the requested

src/buildstream/_stream.py

@@ -1766,7 +1766,7 @@ def _load(
             # rely on state changes during processing to determine which elements
             # must be processed.
             #
-            if selection == _PipelineSelection.NONE:
+            if selection in (_PipelineSelection.NONE, _PipelineSelection.RUN):
                 required_elements = elements
             elif selection == _PipelineSelection.BUILD:
                 required_elements = list(_pipeline.dependencies(elements, _Scope.BUILD, recurse=False))
@@ -1775,8 +1775,13 @@ def _load(
         if not required_elements:
             required_elements = selected
 
+        if selection == _PipelineSelection.NONE:
+            scope = _Scope.NONE
+        else:
+            scope = _Scope.RUN
+
         for element in required_elements:
-            element._set_required()
+            element._set_required(scope)
 
         return selected
 

src/buildstream/data/userconfig.yaml

@@ -93,7 +93,7 @@ build:
   #
   # Control which dependencies to build
   #
-  dependencies: none
+  dependencies: run
 
 
 #

tests/frontend/pull.py

@@ -581,7 +581,15 @@ def test_pull_artifact(cli, tmpdir, datafiles):
 
 
 @pytest.mark.datafiles(DATA_DIR)
-def test_dynamic_build_plan(cli, tmpdir, datafiles):
+@pytest.mark.parametrize(
+    "deps, expected_pulled_elements, expected_states",
+    [
+        ("none", ["checkout-deps.bst"], ("cached", "buildable", "buildable")),
+        ("run", ["import-bin.bst", "checkout-deps.bst"], ("cached", "buildable", "cached")),
+        ("all", ["import-dev.bst", "import-bin.bst", "checkout-deps.bst"], ("cached", "cached", "cached")),
+    ],
+)
+def test_dynamic_build_plan(cli, tmpdir, datafiles, deps, expected_pulled_elements, expected_states):
     project = str(datafiles)
     target = "checkout-deps.bst"
     build_dep = "import-dev.bst"
@@ -610,18 +618,14 @@ def test_dynamic_build_plan(cli, tmpdir, datafiles):
         assert not any(states[e] == "cached" for e in all_elements)
 
         # Now try to rebuild target
-        result = cli.run(project=project, args=["build", target])
+        result = cli.run(project=project, args=["build", "--deps", deps, target])
         result.assert_success()
 
-        # Assert that target and runtime dependency were pulled
-        # but build dependency was not pulled as it wasn't needed
+        # Assert that we only pulled the needed dependencies
         # (dynamic build plan).
-        assert target in result.get_pulled_elements()
-        assert runtime_dep in result.get_pulled_elements()
-        assert build_dep not in result.get_pulled_elements()
+        assert result.get_pulled_elements() == expected_pulled_elements
 
         # And assert that the pulled elements are again in the local cache
         states = cli.get_element_states(project, all_elements)
-        assert states[target] == "cached"
-        assert states[runtime_dep] == "cached"
-        assert states[build_dep] != "cached"
+        states_flattended = (states[target], states[build_dep], states[runtime_dep])
+        assert states_flattended == expected_states