fix: pin the empty kind to installation

Author: Nageshbansal

api/v1alpha1/casting_kind.go

@@ -22,8 +22,9 @@ var (
 	KindInfrastructure  Kind = Kind{s: "Infrastructure"}
 )
 
-// Kind discriminates between top-level casting resource types. Every casting
-// document states its own, so that one file can hold several.
+// Kind discriminates between top-level casting resource types.
+// An empty/missing kind unmarshals to KindInstallation for backwards compatibility
+// with casting files written before kind was introduced.
 type Kind struct {
 	s string
 }
@@ -51,7 +52,8 @@ func (kind *Kind) UnmarshalJSON(text []byte) error {
 
 func (kind *Kind) UnmarshalText(text []byte) error {
 	if len(text) == 0 {
-		return errors.New("kind is required")
+		*kind = KindInstallation
+		return nil
 	}
 
 	for _, available := range Kinds() {

internal/config/yamlconfig/config.go

@@ -172,8 +172,10 @@ func (c *yamlConfig) castings(contents []byte, path string, read func(loader, []
 			return nil, errors.Wrapf(err, errors.TypeInvalidInput, "invalid casting file %s: document %d", path, position)
 		}
 
+		// Empty or missing kind defaults to KindInstallation so existing
+		// castings without `kind` keep working.
 		if probe.Kind == (v1alpha1.Kind{}) {
-			return nil, errors.Newf(errors.TypeInvalidInput, "invalid casting file %s: document %d: kind is required", path, position)
+			probe.Kind = v1alpha1.KindInstallation
 		}
 
 		// A Kind appears at most once: two documents of a Kind would pour into

internal/config/yamlconfig/config_test.go

@@ -457,7 +457,7 @@ spec:
 			expectedError: "Installation is declared twice",
 		},
 		{
-			name: "MissingKind_Invalid",
+			name: "MissingKind_DefaultsToInstallation",
 			contents: `
 apiVersion: v1alpha1
 metadata:
@@ -467,7 +467,8 @@ spec:
     mode: docker
     flavor: compose
 `,
-			expectedError: "kind is required",
+			expectedKinds: []v1alpha1.Kind{v1alpha1.KindInstallation},
+			pass:          true,
 		},
 		{
 			name: "UnknownKind_Invalid",