tpl: Add a warnf template func

Fixes #6628

2 files changed, 18 insertions, 1 deletions

diff --git a/tpl/fmt/fmt.go b/tpl/fmt/fmt.go
index 8b24648cb..7e0258650 100644
--- a/tpl/fmt/fmt.go
+++ b/tpl/fmt/fmt.go
@@ -23,12 +23,16 @@ import (
 
 // New returns a new instance of the fmt-namespaced template functions.
 func New(d *deps.Deps) *Namespace {
-	return &Namespace{helpers.NewDistinctLogger(d.Log.ERROR)}
+	return &Namespace{
+		errorLogger: helpers.NewDistinctLogger(d.Log.ERROR),
+		warnLogger:  helpers.NewDistinctLogger(d.Log.WARN),
+	}
 }
 
 // Namespace provides template functions for the "fmt" namespace.
 type Namespace struct {
 	errorLogger *helpers.DistinctLogger
+	warnLogger  *helpers.DistinctLogger
 }
 
 // Print returns string representation of the passed arguments.
@@ -53,3 +57,10 @@ func (ns *Namespace) Errorf(format string, a ...interface{}) string {
 	ns.errorLogger.Printf(format, a...)
 	return _fmt.Sprintf(format, a...)
 }
+
+// Warnf formats according to a format specifier and logs a WARNING.
+// It returns an empty string.
+func (ns *Namespace) Warnf(format string, a ...interface{}) string {
+	ns.warnLogger.Printf(format, a...)
+	return ""
+}
diff --git a/tpl/fmt/init.go b/tpl/fmt/init.go
index 117055801..14568b45a 100644
--- a/tpl/fmt/init.go
+++ b/tpl/fmt/init.go
@@ -57,6 +57,12 @@ func init() {
 			},
 		)
 
+		ns.AddMethodMapping(ctx.Warnf,
+			[]string{"warnf"},
+			[][2]string{
+				{`{{ warnf "%s." "warning" }}`, ``},
+			},
+		)
 		return ns
 	}