T6946: add function get_tagged_delete_tree to restore tag values

The config diff function produces both del(ete) and sub(tract) trees.
The delete tree contains the minimal path difference between compared
trees, for example, between the active and proposed configs; this is
the information needed to execute removal of a path. The subtract tree
contains the full paths in active that are not in proposed; this retains
necessary information in certain cases. In case all tag values of a tag
node are removed, the delete tree contains only the tag node itself,
however for proper script execution of a deleted tag node, one will need
the removed tag node values: restore this information from the subtract
tree.

1 files changed, 27 insertions, 0 deletions

diff --git a/src/config_diff.ml b/src/config_diff.ml
index 6b84bc8..87b2663 100644
--- a/src/config_diff.ml
+++ b/src/config_diff.ml
@@ -262,6 +262,33 @@ let diff_tree path left right =
     let ret = make Config_tree.default_data "" [add_node; sub_node; del_node; int_node] in
     ret
 
+(* convenience function needed for commit algorithm:
+    we need a hybrid tree between the 'del' tree and the 'sub' tree, namely:
+    in case the del tree has a terminal tag node (== all tag values have
+    been removed) add tag node values for proper removal in commit execution
+    *)
+
+let get_tagged_delete_tree dt =
+    let del_tree = Config_tree.get_subtree dt ["del"] in
+    let sub_tree = Config_tree.get_subtree dt ["sub"] in
+    let f (p, a) _t =
+        let q = List.rev p in
+        match q with
+        | [] -> (p, a)
+        | _ ->
+        if Config_tree.is_tag a q && Vytree.is_terminal_path a q then
+            let children = Vytree.children_of_path sub_tree q in
+            let insert_child path node name =
+                Vytree.insert ~position:Lexical node (path @ [name]) Config_tree.default_data
+            in
+            let a' = List.fold_left (insert_child q) a children in
+            (p, a')
+        else
+            (p, a)
+    in
+    snd (Vytree.fold_tree_with_path f ([], del_tree) del_tree)
+
+
 (* the following builds a diff_func to return a unified diff string of
    configs or config commands
  *)