[cozystack-api] Implement Kubernetes-like defaulting (#1432)

Signed-off-by: Andrei Kvapil <kvapss@gmail.com>

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## What this PR does


### Release note

<!--  Write a release note:
- Explain what has changed internally and for users.
- Start with the same [label] as in the PR title
- Follow the guidelines at
https://github.com/kubernetes/community/blob/master/contributors/guide/release-notes.md.
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```release-note
[]
```

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

- **New Features**
- Application specs now get recursive, Kubernetes-like defaulting:
missing fields in nested objects and arrays are auto-populated safely
without mutating shared defaults.
- No changes to public APIs; existing manifests remain compatible while
gaining broader defaulting.

- **Tests**
- Added unit tests validating defaulting behavior, per-item defaults,
and non-creation of absent keys.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

pkg/registry/apps/application/rest.go

@@ -45,7 +45,6 @@ import (
 	internalapiext "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions"
 	apiextv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
 	structuralschema "k8s.io/apiextensions-apiserver/pkg/apiserver/schema"
-	schemadefault "k8s.io/apiextensions-apiserver/pkg/apiserver/schema/defaulting"
 
 	// Importing API errors package to construct appropriate error responses
 	apierrors "k8s.io/apimachinery/pkg/api/errors"
@@ -89,12 +88,24 @@ type REST struct {
 // NewREST creates a new REST storage for Application with specific configuration
 func NewREST(dynamicClient dynamic.Interface, config *config.Resource) *REST {
 	var specSchema *structuralschema.Structural
+
 	if raw := strings.TrimSpace(config.Application.OpenAPISchema); raw != "" {
-		var js internalapiext.JSONSchemaProps
-		if err := json.Unmarshal([]byte(raw), &js); err != nil {
-			klog.Errorf("Failed to unmarshal OpenAPI schema: %v", err)
-		} else if specSchema, err = structuralschema.NewStructural(&js); err != nil {
-			klog.Errorf("Failed to create structural schema: %v", err)
+		var v1js apiextv1.JSONSchemaProps
+		if err := json.Unmarshal([]byte(raw), &v1js); err != nil {
+			klog.Errorf("Failed to unmarshal v1 OpenAPI schema: %v", err)
+		} else {
+			scheme := runtime.NewScheme()
+			_ = internalapiext.AddToScheme(scheme)
+			_ = apiextv1.AddToScheme(scheme)
+
+			var ijs internalapiext.JSONSchemaProps
+			if err := scheme.Convert(&v1js, &ijs, nil); err != nil {
+				klog.Errorf("Failed to convert v1->internal JSONSchemaProps: %v", err)
+			} else if s, err := structuralschema.NewStructural(&ijs); err != nil {
+				klog.Errorf("Failed to create structural schema: %v", err)
+			} else {
+				specSchema = s
+			}
 		}
 	}
 
@@ -1205,28 +1216,3 @@ func (e errNotAcceptable) Status() metav1.Status {
 		Message: e.Error(),
 	}
 }
-
-// applySpecDefaults applies default values to the Application spec based on the schema
-func (r *REST) applySpecDefaults(app *appsv1alpha1.Application) error {
-	if r.specSchema == nil {
-		return nil
-	}
-	var m map[string]any
-	if app.Spec != nil && len(app.Spec.Raw) > 0 {
-		if err := json.Unmarshal(app.Spec.Raw, &m); err != nil {
-			return err
-		}
-	}
-	if m == nil {
-		m = map[string]any{}
-	}
-
-	schemadefault.Default(m, r.specSchema)
-
-	raw, err := json.Marshal(m)
-	if err != nil {
-		return err
-	}
-	app.Spec = &apiextv1.JSON{Raw: raw}
-	return nil
-}

pkg/registry/apps/application/rest_defaulting.go

@@ -0,0 +1,187 @@
+/*
+Copyright 2024 The Cozystack Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package application
+
+import (
+	"encoding/json"
+	"fmt"
+
+	appsv1alpha1 "github.com/cozystack/cozystack/pkg/apis/apps/v1alpha1"
+	apiextv1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	structuralschema "k8s.io/apiextensions-apiserver/pkg/apiserver/schema"
+)
+
+// applySpecDefaults applies default values to the Application spec based on the schema
+func (r *REST) applySpecDefaults(app *appsv1alpha1.Application) error {
+	if r.specSchema == nil {
+		return nil
+	}
+	var m map[string]any
+	if app.Spec != nil && len(app.Spec.Raw) > 0 {
+		if err := json.Unmarshal(app.Spec.Raw, &m); err != nil {
+			return err
+		}
+	}
+	if m == nil {
+		m = map[string]any{}
+	}
+	if err := defaultLikeKubernetes(&m, r.specSchema); err != nil {
+		return err
+	}
+	raw, err := json.Marshal(m)
+	if err != nil {
+		return err
+	}
+	app.Spec = &apiextv1.JSON{Raw: raw}
+	return nil
+}
+
+func defaultLikeKubernetes(root *map[string]any, s *structuralschema.Structural) error {
+	v := any(*root)
+	nv, err := applyDefaults(v, s, true)
+	if err != nil {
+		return err
+	}
+	obj, ok := nv.(map[string]any)
+	if !ok && nv != nil {
+		return fmt.Errorf("internal error: applyDefaults returned non-map type %T for object root", nv)
+	}
+	if obj == nil {
+		obj = map[string]any{}
+	}
+	*root = obj
+	return nil
+}
+
+func applyDefaults(v any, s *structuralschema.Structural, top bool) (any, error) {
+	if s == nil {
+		return v, nil
+	}
+
+	effType := s.Generic.Type
+	if effType == "" {
+		switch {
+		case len(s.Properties) > 0 || (s.AdditionalProperties != nil && s.AdditionalProperties.Structural != nil):
+			effType = "object"
+		case s.Items != nil:
+			effType = "array"
+		default:
+			// scalar
+		}
+	}
+
+	switch effType {
+	case "object":
+		mv, isMap := v.(map[string]any)
+		if !isMap || v == nil {
+			if s.Generic.Default.Object != nil && !top {
+				if dm, ok := s.Generic.Default.Object.(map[string]any); ok {
+					mv = cloneMap(dm)
+				}
+			}
+			if mv == nil {
+				mv = map[string]any{}
+			}
+		}
+
+		for name, ps := range s.Properties {
+			if _, ok := mv[name]; !ok {
+				if ps.Generic.Default.Object != nil {
+					mv[name] = clone(ps.Generic.Default.Object)
+				}
+			}
+			if cur, ok := mv[name]; ok {
+				cv, err := applyDefaults(cur, &ps, false)
+				if err != nil {
+					return nil, err
+				}
+				mv[name] = cv
+			}
+		}
+
+		if s.AdditionalProperties != nil && s.AdditionalProperties.Structural != nil {
+			ap := s.AdditionalProperties.Structural
+			for k, cur := range mv {
+				if _, isKnown := s.Properties[k]; isKnown {
+					continue
+				}
+				cv, err := applyDefaults(cur, ap, false)
+				if err != nil {
+					return nil, err
+				}
+				mv[k] = cv
+			}
+		}
+		return mv, nil
+
+	case "array":
+		sl, isSlice := v.([]any)
+		if !isSlice || v == nil {
+			if s.Generic.Default.Object != nil {
+				if ds, ok := s.Generic.Default.Object.([]any); ok {
+					sl = cloneSlice(ds)
+				}
+			}
+			if sl == nil {
+				sl = []any{}
+			}
+		}
+		if s.Items != nil {
+			for i := range sl {
+				cv, err := applyDefaults(sl[i], s.Items, false)
+				if err != nil {
+					return nil, err
+				}
+				sl[i] = cv
+			}
+		}
+		return sl, nil
+
+	default:
+		if v == nil && s.Generic.Default.Object != nil {
+			return clone(s.Generic.Default.Object), nil
+		}
+		return v, nil
+	}
+}
+
+func clone(x any) any {
+	switch t := x.(type) {
+	case map[string]any:
+		return cloneMap(t)
+	case []any:
+		return cloneSlice(t)
+	default:
+		return t
+	}
+}
+
+func cloneMap(m map[string]any) map[string]any {
+	out := make(map[string]any, len(m))
+	for k, v := range m {
+		out[k] = clone(v)
+	}
+	return out
+}
+
+func cloneSlice(s []any) []any {
+	out := make([]any, len(s))
+	for i := range s {
+		out[i] = clone(s[i])
+	}
+	return out
+}

pkg/registry/apps/application/rest_defaulting_test.go

@@ -0,0 +1,124 @@
+package application
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+	apischema "k8s.io/apiextensions-apiserver/pkg/apiserver/schema"
+)
+
+func TestApplication(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Application defaulting Suite")
+}
+
+var _ = Describe("defaultLikeKubernetes", func() {
+	var rootSchema *apischema.Structural
+
+	BeforeEach(func() {
+		rootSchema = buildTestSchema()
+	})
+
+	It("applies value-schema defaults to existing map key without merging parent object default", func() {
+		spec := map[string]any{
+			"nodeGroups": map[string]any{
+				"md0": map[string]any{
+					"minReplicas": 3,
+				},
+			},
+		}
+
+		err := defaultLikeKubernetes(&spec, rootSchema)
+		Expect(err).NotTo(HaveOccurred())
+
+		ng := spec["nodeGroups"].(map[string]any)["md0"].(map[string]any)
+
+		Expect(ng).To(HaveKeyWithValue("minReplicas", BeNumerically("==", 3)))
+		Expect(ng).To(HaveKeyWithValue("instanceType", "u1.medium"))
+		Expect(ng["roles"]).To(ConsistOf("ingress-nginx"))
+
+		Expect(ng).NotTo(HaveKey("ephemeralStorage"))
+		Expect(ng).NotTo(HaveKey("maxReplicas"))
+		Expect(ng).NotTo(HaveKey("resources"))
+	})
+
+	It("does not create new map keys from parent object default", func() {
+		spec := map[string]any{
+			"nodeGroups": map[string]any{},
+		}
+
+		err := defaultLikeKubernetes(&spec, rootSchema)
+		Expect(err).NotTo(HaveOccurred())
+
+		ng := spec["nodeGroups"].(map[string]any)
+		Expect(ng).NotTo(HaveKey("md0"))
+	})
+})
+
+func buildTestSchema() *apischema.Structural {
+	instanceType := apischema.Structural{
+		Generic: apischema.Generic{
+			Type:    "string",
+			Default: apischema.JSON{Object: "u1.medium"},
+		},
+	}
+	roles := apischema.Structural{
+		Generic: apischema.Generic{
+			Type:    "array",
+			Default: apischema.JSON{Object: []any{"ingress-nginx"}},
+		},
+		Items: &apischema.Structural{
+			Generic: apischema.Generic{Type: "string"},
+		},
+	}
+	minReplicas := apischema.Structural{
+		Generic: apischema.Generic{Type: "integer"},
+	}
+	ephemeralStorage := apischema.Structural{
+		Generic: apischema.Generic{Type: "string"},
+	}
+	maxReplicas := apischema.Structural{
+		Generic: apischema.Generic{Type: "integer"},
+	}
+	resources := apischema.Structural{
+		Generic:    apischema.Generic{Type: "object"},
+		Properties: map[string]apischema.Structural{},
+	}
+
+	nodeGroupsValue := &apischema.Structural{
+		Generic: apischema.Generic{Type: "object"},
+		Properties: map[string]apischema.Structural{
+			"instanceType":     instanceType,
+			"roles":            roles,
+			"minReplicas":      minReplicas,
+			"ephemeralStorage": ephemeralStorage,
+			"maxReplicas":      maxReplicas,
+			"resources":        resources,
+		},
+	}
+
+	nodeGroups := apischema.Structural{
+		Generic: apischema.Generic{
+			Type: "object",
+			Default: apischema.JSON{Object: map[string]any{
+				"md0": map[string]any{
+					"ephemeralStorage": "20Gi",
+					"maxReplicas":      10,
+					"minReplicas":      0,
+					"resources":        map[string]any{},
+				},
+			}},
+		},
+		AdditionalProperties: &apischema.StructuralOrBool{
+			Structural: nodeGroupsValue,
+		},
+	}
+
+	return &apischema.Structural{
+		Generic: apischema.Generic{Type: "object"},
+		Properties: map[string]apischema.Structural{
+			"nodeGroups": nodeGroups,
+		},
+	}
+}