From defcd18f44a6da04d86ea3d9b71bea8323982c6c Mon Sep 17 00:00:00 2001
From: Virgil <virgil@lethean.io>
Date: Wed, 1 Apr 2026 22:47:37 +0000
Subject: [PATCH] Fix default template fallback for missing vars

---
 executor.go           | 6 +++++-
 modules_infra_test.go | 8 ++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/executor.go b/executor.go
index 56ab214..5150bc7 100644
--- a/executor.go
+++ b/executor.go
@@ -2279,7 +2279,7 @@ func (e *Executor) applyFilter(value, filter string) string {
 
 	// Handle default filter
 	if corexHasPrefix(filter, "default(") {
-		if value == "" || value == "{{ "+filter+" }}" {
+		if value == "" || isUnresolvedTemplateValue(value) {
 			// Extract default value
 			re := regexp.MustCompile(`default\(([^)]*)\)`)
 			if match := re.FindStringSubmatch(filter); len(match) > 1 {
@@ -2318,6 +2318,10 @@ func (e *Executor) applyFilter(value, filter string) string {
 	return value
 }
 
+func isUnresolvedTemplateValue(value string) bool {
+	return corexHasPrefix(value, "{{ ") && corexHasSuffix(value, " }}")
+}
+
 // handleLookup handles lookup() expressions.
 func (e *Executor) handleLookup(expr string) string {
 	// Parse lookup('type', 'arg')
diff --git a/modules_infra_test.go b/modules_infra_test.go
index 21fd61e..9372456 100644
--- a/modules_infra_test.go
+++ b/modules_infra_test.go
@@ -518,6 +518,14 @@ func TestModulesInfra_TemplateString_Good_FilterInTemplate(t *testing.T) {
 	assert.Equal(t, "hello", result)
 }
 
+func TestModulesInfra_TemplateString_Good_DefaultFilterMissingVar(t *testing.T) {
+	e := NewExecutor("/tmp")
+
+	result := e.templateString("{{ missing_var | default('fallback') }}", "", nil)
+
+	assert.Equal(t, "fallback", result)
+}
+
 func TestModulesInfra_TemplateString_Good_DefaultFilterEmptyVar(t *testing.T) {
 	e := NewExecutor("/tmp")
 	e.vars["empty_var"] = ""