[PATCH v2 1/3] tools/bootconfig: Close only opened braces in compact output

[Eduardo Mucelli Rezende Oliveira <edumucelli@gmail.com>]

A key may have both a value and subkeys. When it has only one subkey,
xbc_show_compact_tree() can print that subkey using dotted notation
without opening a brace. During backtracking, however, it treats the
value node followed by a subkey as evidence that a brace was opened.

For example, a.b=v, a.b.c=w and a.z=q are printed with the brace for a
closed before z. Reading that output back changes a.z into the root key
z, silently changing the configuration.

Check the key children when deciding whether to close a brace. Skip the
value child, and account for a sole subkey that itself has both a value
and subkeys, since that combination is not compacted. This follows the
conditions used to open braces without keeping a depth-indexed array.
Extend the mixed-value/subkey sample to cover the lost sibling.

Fixes: e5efaeb8a8f5 ("bootconfig: Support mixing a value and subkeys under a key")
Signed-off-by: Eduardo Mucelli Rezende Oliveira <edumucelli@gmail.com>
---
Changes in v2:
- Determine whether braces were opened from the key children instead of
  keeping the depth-indexed parent array used in v1.
- This handles the deeper value-bearing trees currently accepted by the
  parser without writing beyond a fixed-size array.

Sashiko review:
https://lore.kernel.org/all/sashiko-outbox-207566@kernel.org/

With this valid configuration:

  a.b = v
  a.b.c = w
  a.z = q

the original compact output closes the brace for a before printing z.
Reparsing it turns a.z into the root key z. Values and subkeys under
the same key are allowed by the documented syntax:
https://docs.kernel.org/admin-guide/bootconfig.html#same-key-values

All 94 focused round-trip checks pass with the revision, independently
and in the combined series. The full bootconfig suite also passes.
AddressSanitizer and UBSan checks for 16-, 17-, 20-, 32-, 64- and
95-component value-bearing chains pass for both the first patch alone
and the complete series.

 tools/bootconfig/main.c                       | 29 ++++++++++++++-----
 .../samples/exp-good-mixed-kv1.bconf          |  5 ++++
 tools/bootconfig/samples/good-mixed-kv1.bconf |  5 ++++
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/tools/bootconfig/main.c b/tools/bootconfig/main.c
index 56d76bdeaa09..75516e9e4ac3 100644
--- a/tools/bootconfig/main.c
+++ b/tools/bootconfig/main.c
@@ -68,6 +68,23 @@ static int xbc_show_value(struct xbc_node *node, bool semicolon)
 	return i;
 }
 
+/* Match the conditions under which the compact formatter opens braces. */
+static bool xbc_node_needs_braces(struct xbc_node *node)
+{
+	struct xbc_node *child = xbc_node_get_child(node);
+
+	if (child && xbc_node_is_value(child))
+		child = xbc_node_get_next(child);
+	if (!child)
+		return false;
+	if (child->next)
+		return true;
+
+	/* A single subkey with both a value and subkeys is not compacted. */
+	child = xbc_node_get_child(child);
+	return child && xbc_node_is_value(child) && child->next;
+}
+
 static void xbc_show_compact_tree(void)
 {
 	struct xbc_node *node, *cnode = NULL, *vnode;
@@ -128,14 +145,12 @@ static void xbc_show_compact_tree(void)
 			node = xbc_node_get_parent(node);
 			if (!node)
 				return;
-			if (!xbc_node_get_child(node)->next)
+			if (!depth || !xbc_node_needs_braces(node))
 				continue;
-			if (depth) {
-				depth--;
-				for (i = 0; i < depth; i++)
-					printf("\t");
-				printf("}\n");
-			}
+			depth--;
+			for (i = 0; i < depth; i++)
+				printf("\t");
+			printf("}\n");
 		}
 		node = xbc_node_get_next(node);
 	}
diff --git a/tools/bootconfig/samples/exp-good-mixed-kv1.bconf b/tools/bootconfig/samples/exp-good-mixed-kv1.bconf
index 8346287d9251..0b8b2f59da31 100644
--- a/tools/bootconfig/samples/exp-good-mixed-kv1.bconf
+++ b/tools/bootconfig/samples/exp-good-mixed-kv1.bconf
@@ -1,2 +1,7 @@
 key = "value";
 key.subkey = "another-value";
+a {
+	b = "v";
+	b.c = "w";
+	z = "q";
+}
diff --git a/tools/bootconfig/samples/good-mixed-kv1.bconf b/tools/bootconfig/samples/good-mixed-kv1.bconf
index 1761547dd05c..35442ee62b75 100644
--- a/tools/bootconfig/samples/good-mixed-kv1.bconf
+++ b/tools/bootconfig/samples/good-mixed-kv1.bconf
@@ -1,3 +1,8 @@
 # value -> subkey pattern
 key = value
 key.subkey = another-value
+
+# A valued parent with one subkey must not close its enclosing brace.
+a.b = v
+a.b.c = w
+a.z = q
-- 
2.53.0