feat(variables): allow variable promises to be used directly where template values are

2 files changed, 26 insertions, 6 deletions

diff --git a/gonf/values.go b/gonf/values.go
index 6e37c99..b77e703 100644
--- a/gonf/values.go
+++ b/gonf/values.go
@@ -1,6 +1,9 @@
 package gonf
 
-import "log/slog"
+import (
+	"fmt"
+	"log/slog"
+)
 
 type Value interface {
 	Bytes() []byte
@@ -14,8 +17,11 @@ func interfaceToValue(v any) Value {
 	if vv, ok := v.([]byte); ok {
 		return &BytesValue{vv}
 	}
-	slog.Error("interfaceToTemplateValue", "value", v, "error", "Not Implemented")
-	return nil
+	if vv, ok := v.(*VariablePromise); ok {
+		return vv
+	}
+	slog.Error("interfaceToValue", "value", v, "error", "Not Implemented")
+	panic(fmt.Sprintf("interfaceToValue cannot take type %T as argument. Value was %#v.", v, v))
 }
 
 func interfaceToTemplateValue(v any) Value {
@@ -25,8 +31,11 @@ func interfaceToTemplateValue(v any) Value {
 	if vv, ok := v.([]byte); ok {
 		return &TemplateValue{data: string(vv)}
 	}
+	if vv, ok := v.(*VariablePromise); ok {
+		return vv
+	}
 	slog.Error("interfaceToTemplateValue", "value", v, "error", "Not Implemented")
-	return nil
+	panic(fmt.Sprintf("interfaceToTemplateValue cannot take type %T as argument. Value was %#v.", v, v))
 }
 
 // ----- BytesValue -----------------------------------------------------------------
diff --git a/gonf/variables.go b/gonf/variables.go
index 2c1247c..17f8eb9 100644
--- a/gonf/variables.go
+++ b/gonf/variables.go
@@ -1,6 +1,9 @@
 package gonf
 
-import "log/slog"
+import (
+	"fmt"
+	"log/slog"
+)
 
 // ----- Globals ---------------------------------------------------------------
 var variables map[string]*VariablePromise
@@ -47,12 +50,20 @@ type VariablePromise struct {
 	value     Value
 }
 
+// We want VariablePromise to satisfy the Value interface
+func (s VariablePromise) Bytes() []byte {
+	return s.value.Bytes()
+}
+func (s VariablePromise) String() string {
+	return s.value.String()
+}
+
 // ----- Internal --------------------------------------------------------------
 func getVariable(name string) string {
 	if v, ok := variables[name]; ok {
 		return v.value.String()
 	} else {
 		slog.Error("undefined variable or default", "name", name)
-		return ""
+		panic(fmt.Sprintf("undefined variable or default %s", name))
 	}
 }