_loader/loader: Extract check_circular_deps to utils and Cythonizebschubert/more-cython

- This requires access to 'LoadElement' from _loader/loadelement, we
therefore add a definition file for this module and export it.

1 files changed, 2 insertions, 53 deletions

diff --git a/src/buildstream/_loader/loader.py b/src/buildstream/_loader/loader.py
index 5386eaf00..0767e3687 100644
--- a/src/buildstream/_loader/loader.py
+++ b/src/buildstream/_loader/loader.py
@@ -29,7 +29,7 @@ from .._profile import Topics, PROFILER
 from .._includes import Includes
 
 from .types import Symbol
-from .utils import valid_chars_name
+from .utils import check_circular_deps, valid_chars_name
 from .loadelement import LoadElement, LoadDependency, _extract_depends_from_node
 from .metaelement import MetaElement
 from .metasource import MetaSource
@@ -128,7 +128,7 @@ class Loader():
         )
 
         with PROFILER.profile(Topics.CIRCULAR_CHECK, "_".join(targets)):
-            self._check_circular_deps(dummy_target)
+            check_circular_deps(dummy_target)
 
         ret = []
         #
@@ -327,57 +327,6 @@ class Loader():
         # Nothing more in the queue, return the top level element we loaded.
         return top_element
 
-    # _check_circular_deps():
-    #
-    # Detect circular dependencies on LoadElements with
-    # dependencies already resolved.
-    #
-    # Args:
-    #    element (str): The element to check
-    #
-    # Raises:
-    #    (LoadError): In case there was a circular dependency error
-    #
-    @staticmethod
-    def _check_circular_deps(top_element):
-
-        sequence = [top_element]
-        sequence_indices = [0]
-        check_elements = set(sequence)
-        validated = set()
-
-        while sequence:
-            this_element = sequence[-1]
-            index = sequence_indices[-1]
-            if index < len(this_element.dependencies):
-                element = this_element.dependencies[index].element
-                sequence_indices[-1] = index + 1
-                if element in check_elements:
-                    # Create `chain`, the loop of element dependencies from this
-                    # element back to itself, by trimming everything before this
-                    # element from the sequence under consideration.
-                    chain = [element.full_name for element in sequence[sequence.index(element):]]
-                    chain.append(element.full_name)
-                    raise LoadError(LoadErrorReason.CIRCULAR_DEPENDENCY,
-                                    ("Circular dependency detected at element: {}\n" +
-                                     "Dependency chain: {}")
-                                    .format(element.full_name, " -> ".join(chain)))
-                if element not in validated:
-                    # We've not already validated this element, so let's
-                    # descend into it to check it out
-                    sequence.append(element)
-                    sequence_indices.append(0)
-                    check_elements.add(element)
-                # Otherwise we'll head back around the loop to validate the
-                # next dependency in this entry
-            else:
-                # Done with entry, pop it off, indicate we're no longer
-                # in its chain, and mark it valid
-                sequence.pop()
-                sequence_indices.pop()
-                check_elements.remove(this_element)
-                validated.add(this_element)
-
     # _sort_dependencies():
     #
     # Sort dependencies of each element by their dependencies,