_yaml: Create 'from_dict' on Node and remove node creation methods

Using 'Node.from_dict({})' can replace new_empty_node, and the rest
is not needed anymore.

- Adapt all call sites

8 files changed, 16 insertions, 52 deletions

diff --git a/src/buildstream/_context.py b/src/buildstream/_context.py
index 6977565f2..aa5867bd5 100644
--- a/src/buildstream/_context.py
+++ b/src/buildstream/_context.py
@@ -154,7 +154,7 @@ class Context():
         self._artifactcache = None
         self._sourcecache = None
         self._projects = []
-        self._project_overrides = _yaml.new_empty_node()
+        self._project_overrides = _yaml.Node.from_dict({})
         self._workspaces = None
         self._workspace_project_cache = WorkspaceProjectCache()
         self._cascache = None
diff --git a/src/buildstream/_loader/loader.py b/src/buildstream/_loader/loader.py
index 750df40c9..e45381fbf 100644
--- a/src/buildstream/_loader/loader.py
+++ b/src/buildstream/_loader/loader.py
@@ -120,7 +120,7 @@ class Loader():
 
         # Set up a dummy element that depends on all top-level targets
         # to resolve potential circular dependencies between them
-        dummy_target = LoadElement(_yaml.new_empty_node(), "", self)
+        dummy_target = LoadElement(_yaml.Node.from_dict({}), "", self)
         dummy_target.dependencies.extend(
             LoadElement.Dependency(element, Symbol.RUNTIME)
             for element in target_elements
diff --git a/src/buildstream/_loader/metaelement.py b/src/buildstream/_loader/metaelement.py
index 45eb6f4d0..8214e303d 100644
--- a/src/buildstream/_loader/metaelement.py
+++ b/src/buildstream/_loader/metaelement.py
@@ -48,12 +48,12 @@ class MetaElement():
         self.kind = kind
         self.provenance = provenance
         self.sources = sources
-        self.config = config or _yaml.new_empty_node()
-        self.variables = variables or _yaml.new_empty_node()
-        self.environment = environment or _yaml.new_empty_node()
+        self.config = config or _yaml.Node.from_dict({})
+        self.variables = variables or _yaml.Node.from_dict({})
+        self.environment = environment or _yaml.Node.from_dict({})
         self.env_nocache = env_nocache or []
-        self.public = public or _yaml.new_empty_node()
-        self.sandbox = sandbox or _yaml.new_empty_node()
+        self.public = public or _yaml.Node.from_dict({})
+        self.sandbox = sandbox or _yaml.Node.from_dict({})
         self.build_dependencies = []
         self.dependencies = []
         self.first_pass = first_pass
diff --git a/src/buildstream/_projectrefs.py b/src/buildstream/_projectrefs.py
index c3e669c81..a46765250 100644
--- a/src/buildstream/_projectrefs.py
+++ b/src/buildstream/_projectrefs.py
@@ -87,7 +87,7 @@ class ProjectRefs():
         # Ensure we create our toplevel entry point on the fly here
         for node in [self._toplevel_node, self._toplevel_save]:
             if 'projects' not in node:
-                node['projects'] = _yaml.new_empty_node(ref_node=node)
+                node['projects'] = {}
 
     # lookup_ref()
     #
diff --git a/src/buildstream/_yaml.pyx b/src/buildstream/_yaml.pyx
index d89ba74cb..07209aa1f 100644
--- a/src/buildstream/_yaml.pyx
+++ b/src/buildstream/_yaml.pyx
@@ -71,7 +71,11 @@ cdef class Node:
 
     @classmethod
     def from_dict(cls, dict value):
-        return _new_node_from_dict(value, Node(None, _SYNTHETIC_FILE_INDEX, 0, next_synthetic_counter()))
+        if value:
+            return _new_node_from_dict(value, Node(None, _SYNTHETIC_FILE_INDEX, 0, next_synthetic_counter()))
+        else:
+            # We got an empty dict, we can shortcut
+            return MappingNode({}, _SYNTHETIC_FILE_INDEX, 0, next_synthetic_counter())
 
     cdef bint _walk_find(self, Node target, list path) except *:
         raise NotImplementedError()
@@ -1134,26 +1138,6 @@ def new_synthetic_file(str filename, object project=None):
     return node
 
 
-# new_empty_node()
-#
-# Args:
-#    ref_node (Node): Optional node whose provenance should be referenced
-#
-# Returns
-#    (Node): A new empty YAML mapping node
-#
-def new_empty_node(Node ref_node=None):
-    if ref_node is not None:
-        return MappingNode({}, ref_node.file_index, ref_node.line, next_synthetic_counter())
-    else:
-        return MappingNode({}, _SYNTHETIC_FILE_INDEX, 0, 0)
-
-
-# FIXME: we should never need that
-def new_empty_list_node():
-    return SequenceNode([], _SYNTHETIC_FILE_INDEX, 0, 0)
-
-
 # new_node_from_dict()
 #
 # Args:
diff --git a/src/buildstream/element.py b/src/buildstream/element.py
index 7fb883cf4..39900cffc 100644
--- a/src/buildstream/element.py
+++ b/src/buildstream/element.py
@@ -2510,7 +2510,7 @@ class Element(Plugin):
         # Defaults are loaded once per class and then reused
         #
         if cls.__defaults is None:
-            defaults = _yaml.new_empty_node()
+            defaults = _yaml.Node.from_dict({})
 
             if plugin_conf is not None:
                 # Load the plugin's accompanying .yaml file if one was provided
@@ -2545,7 +2545,7 @@ class Element(Plugin):
         default_env = cls.__defaults.get_mapping("environment", default={})
 
         if meta.is_junction:
-            environment = _yaml.new_empty_node()
+            environment = _yaml.Node.from_dict({})
         else:
             environment = project.base_environment.copy()
 
diff --git a/src/buildstream/plugin.py b/src/buildstream/plugin.py
index fb0516ed2..a6f92ea41 100644
--- a/src/buildstream/plugin.py
+++ b/src/buildstream/plugin.py
@@ -363,26 +363,6 @@ class Plugin():
         provenance = _yaml.node_get_provenance(node, key=member_name)
         return str(provenance)
 
-    def new_empty_node(self):
-        """Create an empty 'Node' object to be handled by BuildStream's core
-        Args:
-           None
-
-        Returns:
-           Node: An empty Node object
-
-        Raises:
-           None
-
-        **Example:**
-
-        .. code:: python
-
-          # Create an empty Node object to store metadata information
-          metadata = self.new_empty_node()
-        """
-        return _yaml.new_empty_node()
-
     def node_get_project_path(self, node, key, *,
                               check_is_file=False, check_is_dir=False):
         """Fetches a project path from a dictionary node and validates it
diff --git a/src/buildstream/sandbox/_sandboxremote.py b/src/buildstream/sandbox/_sandboxremote.py
index e7673f855..d0e641e56 100644
--- a/src/buildstream/sandbox/_sandboxremote.py
+++ b/src/buildstream/sandbox/_sandboxremote.py
@@ -144,7 +144,7 @@ class SandboxRemote(Sandbox):
         # 'url' was the only valid key for remote-execution:
         if 'url' in remote_config:
             if 'execution-service' not in remote_config:
-                exec_config = _yaml.new_node_from_dict({'url': remote_config['url']})
+                exec_config = _yaml.Node.from_dict({'url': remote_config['url']})
             else:
                 provenance = _yaml.node_get_provenance(remote_config, key='url')
                 raise _yaml.LoadError(_yaml.LoadErrorReason.INVALID_DATA,