WIP: Allow symbolic links to subprojectschandan/symbolic-junction

TODO:

- [ ] Decide on the proper name of the "element" configuration option
- [ ] Check if this works in various corner cases
- [ ] Add tests
- [ ] Add docs

2 files changed, 12 insertions, 1 deletions

diff --git a/buildstream/_loader/loader.py b/buildstream/_loader/loader.py
index 6d8310cfa..23612979b 100644
--- a/buildstream/_loader/loader.py
+++ b/buildstream/_loader/loader.py
@@ -578,7 +578,14 @@ class Loader():
             else:
                 raise
 
-        loader = project.loader
+        # Check if an element was specified to use as a symlink
+        if element.junctioned_element:
+            loader = project.loader._get_loader(element.junctioned_element, rewritable=rewritable, ticker=ticker,
+                                                level=level+1, fetch_subprojects=fetch_subprojects,
+                                                provenance=provenance)
+        else:
+            loader = project.loader
+
         self._loaders[filename] = loader
 
         return loader
diff --git a/buildstream/plugins/elements/junction.py b/buildstream/plugins/elements/junction.py
index ec7832bc6..f7ee2ab72 100644
--- a/buildstream/plugins/elements/junction.py
+++ b/buildstream/plugins/elements/junction.py
@@ -48,6 +48,9 @@ Overview
      # Optionally look in a subpath of the source repository for the project
      path: projects/hello
 
+     # Optionally specify the element in the subproject to use as junction
+     element: junctions/sub-project.bst
+
 .. note::
 
    Junction elements may not specify any dependencies as they are simply
@@ -140,6 +143,7 @@ class JunctionElement(Element):
     BST_FORBID_RDEPENDS = True
 
     def configure(self, node):
+        self.junctioned_element = self.node_get_member(node, str, 'element', default=None)
         self.path = self.node_get_member(node, str, 'path', default='')
         self.options = self.node_get_member(node, Mapping, 'options', default={})