T8488: add utility subtree_from_partial

Return the subtree of a configtree indicated by a path that may only be
partly defined, lacking some or all intervening tag node value.

2 files changed, 74 insertions, 0 deletions

diff --git a/src/config_diff.ml b/src/config_diff.ml
index 88756b6..c00705d 100644
--- a/src/config_diff.ml
+++ b/src/config_diff.ml
@@ -769,6 +769,76 @@ let mask_tree ?(exclusive=false) left right =
     let res = eval_diff_result d in
     res.left
 
+(* Convert from a path that may or may not include intervening tag_values,
+   returning a subtree of matches *)
+exception Malformed_path of string
+
+let subtree_from_partial reftree ctree result path =
+    if Util.is_empty path then result
+    else
+    let check_reftree p =
+        match p with
+        | [] -> false
+        | _ ->
+            let rpath =
+                Reference_tree.refpath_from_partial reftree p
+            in
+            match rpath with
+            | [] -> false
+            | _ -> true
+    in
+    let check_ctree p =
+        match p with
+        | [] -> false
+        | _ -> (Vytree.exists[@alert "-exn"]) ctree p
+    in
+    let clone_node tree p =
+        if (Vytree.exists[@alert "-exn"]) tree p then
+            tree
+        else
+        if not ((Vytree.exists[@alert "-exn"]) ctree p) then
+            tree
+        else
+            clone ~recurse:false ctree tree p
+    in
+    let clone_children tree p =
+        let children = Vytree.list_children ((Vytree.get[@alert "-exn"]) ctree p) in
+        let paths = List.map (fun n -> p @ [n]) children in
+        List.fold_left clone_node tree paths
+    in
+    let rec aux acc path_done p =
+        if not (check_reftree (path_done @ p)) then
+            raise (Malformed_path (Util.string_of_list (path_done @ p)))
+        else
+        match path_done, p with
+        | [], h :: tl ->
+                if check_reftree [h] then aux (clone_node acc [h]) [h] tl
+                else
+                raise (Malformed_path (Util.string_of_list p))
+        | _, h :: tl ->
+                let p' = path_done @ [h] in
+                if check_ctree p' then aux (clone_node acc p') p' tl
+                else
+                    if (Config_tree.is_tag[@alert "-exn"]) ctree path_done then
+                    let children =
+                        Vytree.list_children ((Vytree.get[@alert "-exn"]) ctree path_done)
+                    in
+                    let func accum child =
+                        let path = path_done @ [child] @ [h] in
+                        if check_ctree path then
+                            aux (clone_node accum path) path tl
+                        else accum
+                    in
+                    List.fold_left func acc children
+                else
+                (* [h] is a tag_value not present in the config tree *)
+                raise (Malformed_path (Util.string_of_list p'))
+        | _, [] ->
+                if (Config_tree.is_tag[@alert "-exn"]) ctree path_done then clone_children acc path_done
+                else acc
+    in aux result [] path
+
+
 let union_of_values (n : Config_tree.t) (m : Config_tree.t) =
     let set_n = ValueS.of_list (data_of n).values in
     let set_m = ValueS.of_list (data_of m).values in
diff --git a/src/config_diff.mli b/src/config_diff.mli
index 483e7df..168b748 100644
--- a/src/config_diff.mli
+++ b/src/config_diff.mli
@@ -70,3 +70,7 @@ val mask_tree : ?exclusive:bool -> Config_tree.t -> Config_tree.t -> Config_tree
 [@@alert exn "Config_diff.Empty_comparison"]
 
 val get_tagged_delete_tree : Config_tree.t -> Config_tree.t
+
+exception Malformed_path of string
+val subtree_from_partial : Reference_tree.t -> Config_tree.t -> Config_tree.t -> string list -> Config_tree.t
+[@@alert exn "Config_diff.Malformed_path"]