Support root level map keys in map sources

Author: lukasbindreiter

value_source.go

@@ -189,12 +189,19 @@ func (ms *mapSource) GoString() string {
 	return fmt.Sprintf("&mapSource{name:%[1]q}", ms.name)
 }
 
+// Lookup returns a value from the map source. The lookup name may be a dot-separated path into the map.
+// If that is the case, it will recursively traverse the map based on the '.' delimited sections to find
+// a nested value for the key.
 func (ms *mapSource) Lookup(name string) (any, bool) {
-	// nestedVal checks if the name has '.' delimiters.
-	// If so, it tries to traverse the tree by the '.' delimited sections to find
-	// a nested value for the key.
-	if sections := strings.Split(name, "."); len(sections) > 1 {
-		node := ms.m
+	sections := strings.Split(name, ".")
+	if name == "" || len(sections) == 0 {
+		return nil, false
+	}
+
+	node := ms.m
+
+	// traverse into the map based on the dot-separated sections
+	if len(sections) >= 2 { // the last section is the value we want, we will return it directly at the end
 		for _, section := range sections[:len(sections)-1] {
 			child, ok := node[section]
 			if !ok {
@@ -213,11 +220,11 @@ func (ms *mapSource) Lookup(name string) (any, bool) {
 				return nil, false
 			}
 		}
-		if val, ok := node[sections[len(sections)-1]]; ok {
-			return val, true
-		}
 	}
 
+	if val, ok := node[sections[len(sections)-1]]; ok {
+		return val, true
+	}
 	return nil, false
 }
 

value_source_test.go

@@ -221,6 +221,15 @@ func TestMapValueSource(t *testing.T) {
 				"foo": 10,
 			},
 		},
+		{
+			name: "Level 1",
+			key:  "foobar",
+			m: map[any]any{
+				"foobar": 10,
+			},
+			val:   "10",
+			found: true,
+		},
 		{
 			name: "Level 2",
 			key:  "foo.bar",
@@ -241,6 +250,15 @@ func TestMapValueSource(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "Level 2 string map type",
+			key:  "foo.bar1",
+			m: map[any]any{
+				"foo": map[string]any{
+					"bar": "10",
+				},
+			},
+		},
 		{
 			name: "Level 3 no entry",
 			key:  "foo.bar.t",