Add handling of updates to a field's enum values to the CRD Upgrade Safety preflight check

pkg/kapp/crdupgradesafety/change_validator.go

@@ -0,0 +1,216 @@
+// Copyright 2024 The Carvel Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+package crdupgradesafety
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+
+	"github.com/openshift/crd-schema-checker/pkg/manifestcomparators"
+	v1 "k8s.io/apiextensions-apiserver/pkg/apis/apiextensions/v1"
+	"k8s.io/apimachinery/pkg/util/sets"
+	"k8s.io/apimachinery/pkg/util/validation/field"
+)
+
+// ChangeValidation is a function that accepts a FieldDiff
+// as a parameter and should return:
+// - a boolean representation of whether or not the change
+// - an error if the change would be unsafe
+// has been fully handled (i.e no additional changes exist)
+type ChangeValidation func(diff FieldDiff) (bool, error)
+
+// EnumChangeValidation ensures that:
+// - No enums are added to a field that did not previously have
+// enum restrictions
+// - No enums are removed from a field
+// This function returns:
+// - A boolean representation of whether or not the change
+// has been fully handled (i.e the only change was to enum values)
+// - An error if either of the above validations are not satisfied
+func EnumChangeValidation(diff FieldDiff) (bool, error) {
+	// This function resets the enum values for the
+	// old and new field and compares them to determine
+	// if there are any additional changes that should be
+	// handled. Reseting the enum values allows for chained
+	// evaluations to check if they have handled all the changes
+	// without having to account for fields other than the ones
+	// they are designed to handle. This function should only be called when
+	// returning from this function to prevent unnecessary overwrites of
+	// these fields.
+	handled := func() bool {
+		diff.Old.Enum = []v1.JSON{}
+		diff.New.Enum = []v1.JSON{}
+		return reflect.DeepEqual(diff.Old, diff.New)
+	}
+
+	if len(diff.Old.Enum) == 0 && len(diff.New.Enum) > 0 {
+		return handled(), fmt.Errorf("enums added when there were no enum restrictions previously")
+	}
+
+	oldSet := sets.NewString()
+	for _, enum := range diff.Old.Enum {
+		if !oldSet.Has(string(enum.Raw)) {
+			oldSet.Insert(string(enum.Raw))
+		}
+	}
+
+	newSet := sets.NewString()
+	for _, enum := range diff.New.Enum {
+		if !newSet.Has(string(enum.Raw)) {
+			newSet.Insert(string(enum.Raw))
+		}
+	}
+
+	diffSet := oldSet.Difference(newSet)
+	if diffSet.Len() > 0 {
+		return handled(), fmt.Errorf("enum values removed: %+v", diffSet.UnsortedList())
+	}
+
+	return handled(), nil
+}
+
+// ChangeValidator is a Validation implementation focused on
+// handling updates to existing fields in a CRD
+type ChangeValidator struct {
+	// Validations is a slice of ChangeValidations
+	// to run against each changed field
+	Validations []ChangeValidation
+}
+
+func (cv *ChangeValidator) Name() string {
+	return "ChangeValidator"
+}
+
+// Validate will compare each version in the provided existing and new CRDs.
+// Since the ChangeValidator is tailored to handling updates to existing fields in
+// each version of a CRD. As such the following is assumed:
+// - Validating the removal of versions during an update is handled outside of this
+// validator. If a version in the existing version of the CRD does not exist in the new
+// version that version of the CRD is skipped in this validator.
+// - Removal of existing fields is unsafe. Regardless of whether or not this is handled
+// by a validator outside this one, if a field is present in a version provided by the existing CRD
+// but not present in the same version provided by the new CRD this validation will fail.
+//
+// Additionally, any changes that are not validated and handled by the known ChangeValidations
+// are deemed as unsafe and returns an error.
+func (cv *ChangeValidator) Validate(old, new v1.CustomResourceDefinition) error {
+	errs := []error{}
+	for _, version := range old.Spec.Versions {
+		newVersion := manifestcomparators.GetVersionByName(&new, version.Name)
+		if newVersion == nil {
+			// if the new version doesn't exist skip this version
+			continue
+		}
+		flatOld := FlattenSchema(version.Schema.OpenAPIV3Schema)
+		flatNew := FlattenSchema(newVersion.Schema.OpenAPIV3Schema)
+
+		diffs, err := CalculateFlatSchemaDiff(flatOld, flatNew)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("calculating schema diff for CRD version %q", version.Name))
+			continue
+		}
+
+		for field, diff := range diffs {
+			handled := false
+			for _, validation := range cv.Validations {
+				ok, err := validation(diff)
+				if err != nil {
+					errs = append(errs, fmt.Errorf("version %q, field %q: %w", version.Name, field, err))
+				}
+				if ok {
+					handled = true
+					break
+				}
+			}
+
+			if !handled {
+				errs = append(errs, fmt.Errorf("version %q, field %q has unknown change, refusing to determine that change is safe", version.Name, field))
+			}
+		}
+	}
+
+	if len(errs) > 0 {
+		return errors.Join(errs...)
+	}
+	return nil
+}
+
+type FieldDiff struct {
+	Old *v1.JSONSchemaProps
+	New *v1.JSONSchemaProps
+}
+
+// FlatSchema is a flat representation of a CRD schema.
+type FlatSchema map[string]*v1.JSONSchemaProps
+
+// FlattenSchema takes in a CRD version OpenAPIV3Schema and returns
+// a flattened representation of it. For example, a CRD with a schema of:
+// ```yaml
+//
+//	...
+//	spec:
+//	  type: object
+//	  properties:
+//	    foo:
+//	      type: string
+//	    bar:
+//	      type: string
+//	...
+//
+// ```
+// would be represented as:
+//
+//	map[string]*v1.JSONSchemaProps{
+//	   "^": {},
+//	   "^.spec": {},
+//	   "^.spec.foo": {},
+//	   "^.spec.bar": {},
+//	}
+//
+// where "^" represents the "root" schema
+func FlattenSchema(schema *v1.JSONSchemaProps) FlatSchema {
+	fieldMap := map[string]*v1.JSONSchemaProps{}
+
+	manifestcomparators.SchemaHas(schema,
+		field.NewPath("^"),
+		field.NewPath("^"),
+		nil,
+		func(s *v1.JSONSchemaProps, _, simpleLocation *field.Path, _ []*v1.JSONSchemaProps) bool {
+			fieldMap[simpleLocation.String()] = s.DeepCopy()
+			return false
+		})
+
+	return fieldMap
+}
+
+// CalculateFlatSchemaDiff finds fields in a FlatSchema that are different
+// and returns a mapping of field --> old and new field schemas. If a field
+// exists in the old FlatSchema but not the new an empty diff mapping and an error is returned.
+func CalculateFlatSchemaDiff(o, n FlatSchema) (map[string]FieldDiff, error) {
+	diffMap := map[string]FieldDiff{}
+	for field, schema := range o {
+		if _, ok := n[field]; !ok {
+			return diffMap, fmt.Errorf("field %q in existing not found in new", field)
+		}
+		newSchema := n[field]
+
+		// Copy the schemas and remove any child properties for comparison.
+		// In theory this will focus in on detecting changes for only the
+		// field we are looking at and ignore changes in the children fields.
+		// Since we are iterating through the map that should have all fields
+		// we should still detect changes in the children fields.
+		oldCopy := schema.DeepCopy()
+		newCopy := newSchema.DeepCopy()
+		oldCopy.Properties = nil
+		newCopy.Properties = nil
+		if !reflect.DeepEqual(oldCopy, newCopy) {
+			diffMap[field] = FieldDiff{
+				Old: oldCopy,
+				New: newCopy,
+			}
+		}
+	}
+	return diffMap, nil
+}