packer: verify `except` has valid builders [GH-438]

packer/template.go

@@ -563,5 +563,12 @@ func (t *TemplateOnlyExcept) Validate(b map[string]RawBuilderConfig) (e []error)
 		}
 	}
 
+	for _, n := range t.Except {
+		if _, ok := b[n]; !ok {
+			e = append(e,
+				fmt.Errorf("'except' specified builder '%s' not found", n))
+		}
+	}
+
 	return
 }

packer/template_test.go

@@ -707,7 +707,7 @@ func TestTemplateBuild_exeptPPInvalid(t *testing.T) {
 		"post-processors": [
 			{
 				"type": "test-pp",
-				"except": "test5"
+				"except": ["test5"]
 			}
 		]
 	}
@@ -787,7 +787,7 @@ func TestTemplateBuild_exceptProvInvalid(t *testing.T) {
 		"provisioners": [
 			{
 				"type": "test-prov",
-				"except": "test5"
+				"except": ["test5"]
 			}
 		]
 	}
@@ -867,7 +867,7 @@ func TestTemplateBuild_onlyPPInvalid(t *testing.T) {
 		"post-processors": [
 			{
 				"type": "test-pp",
-				"only": "test5"
+				"only": ["test5"]
 			}
 		]
 	}
@@ -947,7 +947,7 @@ func TestTemplateBuild_onlyProvInvalid(t *testing.T) {
 		"provisioners": [
 			{
 				"type": "test-prov",
-				"only": "test5"
+				"only": ["test5"]
 			}
 		]
 	}