Propagate patch directive decode errors

Signed-off-by: kahirokunn <okinakahiro@gmail.com>

Author: kahirokunn

pkg/reconciler/common/patches.go

@@ -245,7 +245,7 @@ func validatePatchDirectives(patchType base.PatchType, patchJSON []byte) error {
 	if patchType != base.StrategicMergePatchType {
 		var patchDocument interface{}
 		if err := json.Unmarshal(patchJSON, &patchDocument); err != nil {
-			return nil
+			return fmt.Errorf("decode patch document: %w", err)
 		}
 		if containsPatchDirective(patchDocument) {
 			return errors.New("$patch directive is only supported for the strategic merge patch type")

pkg/reconciler/common/patches_test.go

@@ -526,6 +526,17 @@ spec:
 	}
 }
 
+func TestValidatePatchDirectivesReturnsDecodeError(t *testing.T) {
+	for _, patchType := range []base.PatchType{base.JSONPatchType, base.MergePatchType} {
+		t.Run(string(patchType), func(t *testing.T) {
+			err := validatePatchDirectives(patchType, []byte(`{`))
+			if err == nil || !strings.Contains(err.Error(), "decode patch document") {
+				t.Fatalf("validatePatchDirectives() = %v, want decode patch document error", err)
+			}
+		})
+	}
+}
+
 func TestResourcePatchRunsAfterBuiltInTransforms(t *testing.T) {
 	replicas := int32(5)
 	instance := &v1beta1.KnativeServing{