From 47dcfa0642fbcdda3aa27b4aa954f46aa4a45b17 Mon Sep 17 00:00:00 2001
From: Michal Gorecki <michal.gorecki@codecoup.pl>
Date: Fri, 16 May 2025 13:41:16 +0200
Subject: [PATCH] newt/syscfg: Expand nested MYNEWT_VAL references

Now Newt will resolve references of nested MYNEWT_VAL references.

Example:
CONFIG_A: MYNEWT_VAL(CONFIG_B)
CONFIG_B: MYNEWT_VAL(CONFIG_C)
CONFIG_C: 1

Before this change the outcome of this configuration would
depend on configs resolution order.
If CONFIG_A would be resolved before CONFIG_B the final outcome would be:
CONFIG_A: 'MYNEWT_VAL(CONFIG_C)' <- string copied from not yet resolved CONFIG_B
CONFIG_B: 1
CONFIG_C: 1

Now all the configs will get value 1, as expected.
---
 newt/syscfg/syscfg.go  | 23 ++++++++++++++++++-----
 newt/val/valsetting.go |  3 +--
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/newt/syscfg/syscfg.go b/newt/syscfg/syscfg.go
index 886699cca..3efa42490 100644
--- a/newt/syscfg/syscfg.go
+++ b/newt/syscfg/syscfg.go
@@ -209,20 +209,33 @@ func ResolveValueRefName(val string) string {
 }
 
 func (cfg *Cfg) ExpandRef(val string) (string, string, error) {
+	var visited []string
+	var entry CfgEntry
+	var ok bool
+
 	refName := ResolveValueRefName(val)
 	if refName == "" {
 		// Not a reference.
 		return "", val, nil
 	}
 
-	entry, ok := cfg.Settings[refName]
-	if !ok {
-		return "", "", util.FmtNewtError(
-			"setting value \"%s\" references undefined setting", val)
+	for refName != "" {
+		entry, ok = cfg.Settings[refName]
+		if !ok {
+			return "", "", util.FmtNewtError(
+				"setting value \"%s\" references undefined setting", val)
+		}
+		for _, v := range visited {
+			if entry.Name == v {
+				return "", "", util.FmtNewtError(
+					"setting value \"%s\" creates a reference loop", entry.Name)
+			}
+		}
+		visited = append(visited, entry.Name)
+		refName = ResolveValueRefName(entry.Value)
 	}
 
 	return entry.Name, entry.Value, nil
-
 }
 
 func (cfg *Cfg) AddInjectedSettings() {
diff --git a/newt/val/valsetting.go b/newt/val/valsetting.go
index 0d24218a7..78c3e54e1 100644
--- a/newt/val/valsetting.go
+++ b/newt/val/valsetting.go
@@ -57,8 +57,7 @@ func (vs *ValSetting) IntVal() (int, error) {
 func ResolveValSetting(s string, cfg *syscfg.Cfg) (ValSetting, error) {
 	refName, val, err := cfg.ExpandRef(s)
 	if err != nil {
-		return ValSetting{},
-			util.FmtNewtError("value \"%s\" references undefined setting", s)
+		return ValSetting{}, err
 	}
 
 	return ValSetting{