feat: add builtin runtime support

Signed-off-by: Abdulrahman Fikry <[email protected]>

Author: abdulrahman11a

go.mod

@@ -11,7 +11,7 @@ require (
 	github.com/google/go-containerregistry v0.20.6
 	github.com/google/shlex v0.0.0-20191202100458-e7afc7fbc510
 	github.com/kptdev/krm-functions-catalog/functions/go/apply-setters v0.2.2
-	github.com/kptdev/krm-functions-sdk/go/fn v1.0.0
+	github.com/kptdev/krm-functions-sdk/go/fn v1.0.2
 	github.com/otiai10/copy v1.14.1
 	github.com/philopon/go-toposort v0.0.0-20170620085441-9be86dbd762f
 	github.com/pkg/errors v0.9.1
@@ -43,8 +43,11 @@ require (
 
 require (
 	cloud.google.com/go/compute/metadata v0.9.0 // indirect
+	github.com/360EntSecGroup-Skylar/excelize v1.4.1 // indirect
 	github.com/Azure/go-ansiterm v0.0.0-20250102033503-faa5f7b0171c // indirect
 	github.com/MakeNowJust/heredoc v1.0.0 // indirect
+	github.com/PuerkitoBio/goquery v1.5.1 // indirect
+	github.com/andybalholm/cascadia v1.1.0 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/blang/semver/v4 v4.0.0 // indirect
 	github.com/cespare/xxhash/v2 v2.3.0 // indirect
@@ -55,6 +58,7 @@ require (
 	github.com/docker/distribution v2.8.3+incompatible // indirect
 	github.com/docker/docker-credential-helpers v0.9.4 // indirect
 	github.com/docker/libtrust v0.0.0-20160708172513-aabc10ec26b7 // indirect
+	github.com/dustmop/soup v1.1.2-0.20190516214245-38228baa104e // indirect
 	github.com/emicklei/go-restful/v3 v3.13.0 // indirect
 	github.com/evanphx/json-patch/v5 v5.9.11 // indirect
 	github.com/exponent-io/jsonpath v0.0.0-20210407135951-1de76d718b3f // indirect
@@ -85,26 +89,30 @@ require (
 	github.com/jonboulle/clockwork v0.5.0 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
 	github.com/klauspost/compress v1.18.2 // indirect
+	github.com/kptdev/krm-functions-catalog/functions/go/starlark v0.5.5 // indirect
 	github.com/liggitt/tabwriter v0.0.0-20181228230101-89fcab3d43de // indirect
 	github.com/mitchellh/go-homedir v1.1.0 // indirect
 	github.com/mitchellh/go-wordwrap v1.0.1 // indirect
 	github.com/moby/spdystream v0.5.0 // indirect
 	github.com/moby/term v0.5.2 // indirect
 	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
 	github.com/modern-go/reflect2 v1.0.3-0.20250322232337-35a7c28c31ee // indirect
+	github.com/mohae/deepcopy v0.0.0-20170929034955-c48cc78d4826 // indirect
 	github.com/monochromegane/go-gitignore v0.0.0-20200626010858-205db1a8cc00 // indirect
 	github.com/munnerz/goautoneg v0.0.0-20191010083416-a7dc8b61c822 // indirect
 	github.com/mxk/go-flowrate v0.0.0-20140419014527-cca7078d478f // indirect
 	github.com/onsi/gomega v1.37.0 // indirect
 	github.com/opencontainers/go-digest v1.0.0 // indirect
 	github.com/opencontainers/image-spec v1.1.1 // indirect
 	github.com/otiai10/mint v1.6.3 // indirect
+	github.com/paulmach/orb v0.1.5 // indirect
 	github.com/peterbourgon/diskv v2.0.1+incompatible // indirect
 	github.com/pmezard/go-difflib v1.0.1-0.20181226105442-5d4384ee4fb2 // indirect
 	github.com/prometheus/client_golang v1.23.2 // indirect
 	github.com/prometheus/client_model v0.6.2 // indirect
 	github.com/prometheus/common v0.67.2 // indirect
 	github.com/prometheus/procfs v0.19.2 // indirect
+	github.com/qri-io/starlib v0.5.0 // indirect
 	github.com/russross/blackfriday/v2 v2.1.0 // indirect
 	github.com/sergi/go-diff v1.4.0 // indirect
 	github.com/sirupsen/logrus v1.9.3 // indirect
@@ -114,6 +122,7 @@ require (
 	github.com/x448/float16 v0.8.4 // indirect
 	go.opentelemetry.io/otel v1.38.0 // indirect
 	go.opentelemetry.io/otel/trace v1.38.0 // indirect
+	go.starlark.net v0.0.0-20250417143717-f57e51f710eb // indirect
 	go.yaml.in/yaml/v2 v2.4.3 // indirect
 	go.yaml.in/yaml/v3 v3.0.4 // indirect
 	golang.org/x/net v0.47.0 // indirect

go.sum

@@ -0,0 +1,22 @@
+// Copyright 2026 The kpt 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 builtins registers all built-in KRM functions into the builtin registry.
+package builtins
+
+import (
+	// Register built-in functions via init()
+	_ "github.com/kptdev/kpt/internal/builtins/applyreplacements"
+	_ "github.com/kptdev/kpt/internal/builtins/starlark"
+)

internal/builtins/BuiltinRuntime.go

@@ -0,0 +1,122 @@
+// Copyright 2026 The kpt 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 applyreplacements
+
+import (
+	"fmt"
+	"io"
+
+	"github.com/kptdev/kpt/internal/builtins/registry"
+	"github.com/kptdev/krm-functions-sdk/go/fn"
+	"sigs.k8s.io/kustomize/api/filters/replacement"
+	"sigs.k8s.io/kustomize/api/types"
+	"sigs.k8s.io/kustomize/kyaml/yaml"
+)
+
+const (
+	ImageName          = "ghcr.io/kptdev/krm-functions-catalog/apply-replacements"
+	fnConfigKind       = "ApplyReplacements"
+	fnConfigAPIVersion = "fn.kpt.dev/v1alpha1"
+)
+
+func init() {
+	registry.Register(&ApplyReplacementsRunner{})
+}
+
+type ApplyReplacementsRunner struct{}
+
+func (a *ApplyReplacementsRunner) ImageName() string { return ImageName }
+
+func (a *ApplyReplacementsRunner) Run(r io.Reader, w io.Writer) error {
+	input, err := io.ReadAll(r)
+	if err != nil {
+		return fmt.Errorf("reading input: %w", err)
+	}
+	rl, err := fn.ParseResourceList(input)
+	if err != nil {
+		return fmt.Errorf("parsing ResourceList: %w", err)
+	}
+	if _, err := applyReplacements(rl); err != nil {
+		return err
+	}
+	out, err := rl.ToYAML()
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(out)
+	return err
+}
+func applyReplacements(rl *fn.ResourceList) (bool, error) {
+	r := &Replacements{}
+	return r.Process(rl)
+}
+
+type Replacements struct {
+	Replacements []types.Replacement `json:"replacements,omitempty" yaml:"replacements,omitempty"`
+}
+
+func (r *Replacements) Config(functionConfig *fn.KubeObject) error {
+	if functionConfig.IsEmpty() {
+		return fmt.Errorf("FunctionConfig is missing. Expect `ApplyReplacements`")
+	}
+	if functionConfig.GetKind() != fnConfigKind || functionConfig.GetAPIVersion() != fnConfigAPIVersion {
+		return fmt.Errorf("received functionConfig of kind %s and apiVersion %s, only functionConfig of kind %s and apiVersion %s is supported",
+			functionConfig.GetKind(), functionConfig.GetAPIVersion(), fnConfigKind, fnConfigAPIVersion)
+	}
+	r.Replacements = []types.Replacement{}
+	if err := functionConfig.As(r); err != nil {
+		return fmt.Errorf("unable to convert functionConfig to replacements:\n%w", err)
+	}
+	return nil
+}
+
+func (r *Replacements) Process(rl *fn.ResourceList) (bool, error) {
+	if err := r.Config(rl.FunctionConfig); err != nil {
+		rl.LogResult(err)
+		return false, nil
+	}
+	transformedItems, err := r.Transform(rl.Items)
+	if err != nil {
+		rl.LogResult(err)
+		return false, nil
+	}
+	rl.Items = transformedItems
+	return true, nil
+}
+
+func (r *Replacements) Transform(items []*fn.KubeObject) ([]*fn.KubeObject, error) {
+	var transformedItems []*fn.KubeObject
+	var nodes []*yaml.RNode
+	for _, obj := range items {
+		objRN, err := yaml.Parse(obj.String())
+		if err != nil {
+			return nil, err
+		}
+		nodes = append(nodes, objRN)
+	}
+	transformedNodes, err := replacement.Filter{
+		Replacements: r.Replacements,
+	}.Filter(nodes)
+	if err != nil {
+		return nil, err
+	}
+	for _, n := range transformedNodes {
+		obj, err := fn.ParseKubeObject([]byte(n.MustString()))
+		if err != nil {
+			return nil, err
+		}
+		transformedItems = append(transformedItems, obj)
+	}
+	return transformedItems, nil
+}

internal/builtins/applyreplacements/apply_replacements.go

@@ -0,0 +1,67 @@
+// Copyright 2026 The kpt 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 registry
+
+import (
+	"io"
+	"strings"
+	"sync"
+)
+
+type BuiltinFunction interface {
+	ImageName() string
+	Run(r io.Reader, w io.Writer) error
+}
+
+var (
+	mu       sync.RWMutex
+	registry = map[string]BuiltinFunction{}
+)
+
+func Register(fn BuiltinFunction) {
+	mu.Lock()
+	defer mu.Unlock()
+	registry[normalizeImage(fn.ImageName())] = fn
+}
+
+func Lookup(imageName string) BuiltinFunction {
+	mu.RLock()
+	defer mu.RUnlock()
+	return registry[normalizeImage(imageName)]
+}
+
+func List() []string {
+	mu.RLock()
+	defer mu.RUnlock()
+	names := make([]string, 0, len(registry))
+	for name := range registry {
+		names = append(names, name)
+	}
+	return names
+}
+
+func normalizeImage(image string) string {
+	if idx := strings.Index(image, "@"); idx != -1 {
+		image = image[:idx]
+	}
+	parts := strings.Split(image, "/")
+	if len(parts) > 0 {
+		last := parts[len(parts)-1]
+		if idx := strings.Index(last, ":"); idx != -1 {
+			parts[len(parts)-1] = last[:idx]
+		}
+	}
+	return strings.Join(parts, "/")
+}