_yaml: Introduce 'get_sequence()' and 'sequence_at()'/'mapping_at()'

- Adding 'get_sequence' on MappingNode to access sequences in a mapping
- Adding 'sequence_at' on SequenceNode to access sequences in a sequence
- Adding 'mapping_at' on SequenceNode to access mappings in a sequence

Using "*_at" in sequences allows us to quickly understand if we are
dealing with a sequence or a mapping.

2 files changed, 10 insertions, 12 deletions

diff --git a/src/buildstream/_loader/loader.py b/src/buildstream/_loader/loader.py
index 5f533731b..64e7fafd0 100644
--- a/src/buildstream/_loader/loader.py
+++ b/src/buildstream/_loader/loader.py
@@ -466,13 +466,12 @@ class Loader():
         elt_provenance = _yaml.node_get_provenance(node)
         meta_sources = []
 
-        sources = _yaml.node_get(node, list, Symbol.SOURCES, default_value=[])
+        sources = node.get_sequence(Symbol.SOURCES, default=[])
         element_kind = node.get_str(Symbol.KIND)
 
         # Safe loop calling into _yaml.node_get() for each element ensures
         # we have good error reporting
-        for i in range(len(sources)):
-            source = _yaml.node_get(node, dict, Symbol.SOURCES, indices=[i])
+        for index, source in enumerate(sources):
             kind = source.get_str(Symbol.KIND)
             _yaml.node_del(source, Symbol.KIND)
 
@@ -481,7 +480,6 @@ class Loader():
             if directory:
                 _yaml.node_del(source, Symbol.DIRECTORY)
 
-            index = sources.index(source)
             meta_source = MetaSource(element.name, index, element_kind, kind, source, directory)
             meta_sources.append(meta_source)
 
@@ -490,7 +488,7 @@ class Loader():
                                    node.get_mapping(Symbol.CONFIG, default={}),
                                    node.get_mapping(Symbol.VARIABLES, default={}),
                                    node.get_mapping(Symbol.ENVIRONMENT, default={}),
-                                   _yaml.node_get(node, list, Symbol.ENV_NOCACHE, default_value=[]),
+                                   node.get_sequence(Symbol.ENV_NOCACHE, default=[]).as_str_list(),
                                    node.get_mapping(Symbol.PUBLIC, default={}),
                                    node.get_mapping(Symbol.SANDBOX, default={}),
                                    element_kind == 'junction')
diff --git a/src/buildstream/_loader/types.pyx b/src/buildstream/_loader/types.pyx
index a3e49b040..dfd8f9046 100644
--- a/src/buildstream/_loader/types.pyx
+++ b/src/buildstream/_loader/types.pyx
@@ -72,8 +72,8 @@ cdef class Dependency:
 
         self.provenance = provenance
 
-        if type(dep) is str:
-            self.name = <str> dep
+        if type(dep) is _yaml.ScalarNode:
+            self.name = dep.as_str()
             self.dep_type = default_dep_type
             self.junction = None
 
@@ -138,15 +138,15 @@ cdef class Dependency:
 #    acc (list): a list in which to add the loaded dependencies
 #
 cdef void _extract_depends_from_node(_yaml.Node node, str key, str default_dep_type, list acc) except *:
-    cdef list depends = <list> _yaml.node_get(node, list, key, None, [])
-    cdef int index
+    cdef _yaml.SequenceNode depends = node.get_sequence(key, [])
+    cdef _yaml.Node dep_node
     cdef _yaml.ProvenanceInformation dep_provenance
 
-    for index in range(len(depends)):
+    for dep_node in depends:
         # FIXME: the provenance information would be obtainable from the Node directly if we stop
         #        stripping provenance and have proper nodes for str elements
-        dep_provenance = <_yaml.ProvenanceInformation> _yaml.node_get_provenance(node, key=key, indices=[index])
-        dependency = Dependency(depends[index], dep_provenance, default_dep_type=default_dep_type)
+        dep_provenance = <_yaml.ProvenanceInformation> _yaml.node_get_provenance(dep_node)
+        dependency = Dependency(dep_node, dep_provenance, default_dep_type=default_dep_type)
         acc.append(dependency)
 
     # Now delete the field, we dont want it anymore