Basic config map generator function (#347)

krm-functions/gen-configmap-fn/.gitignore

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+_actual_output.yaml

krm-functions/gen-configmap-fn/Dockerfile

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+#  Copyright 2023 The Nephio 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.
+
+FROM golang:1.20-alpine
+ENV CGO_ENABLED=0
+WORKDIR /go/src/
+COPY krm-functions/ krm-functions/
+WORKDIR /go/src/krm-functions/gen-configmap-fn
+RUN go install
+RUN go build -o /usr/local/bin/function ./
+
+FROM gcr.io/distroless/static:latest
+COPY --from=0 /usr/local/bin/function /usr/local/bin/function
+ENTRYPOINT ["function"]

krm-functions/gen-configmap-fn/Makefile

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+IMAGE_TAG ?= latest
+REGISTRY ?= docker.io/nephio
+IMAGE_NAME ?= gen-configmap-fn
+IMG ?= $(REGISTRY)/$(IMAGE_NAME):$(IMAGE_TAG)
+
+# This includes the following targets:
+#   test, unit, unit-clean,
+#   gosec, lint,
+#   fmt, vet
+include ../../default-go.mk
+
+# This includes the following targets:
+#   docker-build, docker-push
+include ../../default-docker.mk
+
+# This includes the 'help' target that prints out all targets with their descriptions organized by categories
+include ../../default-help.mk
+
+.PHONY: all
+all: fmt test docker-build docker-push

krm-functions/gen-configmap-fn/README.md

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+# gen-configmap-fn
+
+## Overview
+
+<!--mdtogo:Short-->
+
+This function is a simple ConfigMap generator.
+
+<!--mdtogo-->
+
+Application config is often captured in ConfigMaps, but it is difficult to edit
+the contents of the ConfigMap with KRM functions. This allows function inputs to
+be used to generate ConfigMaps, and those inputs can be more easily edited than
+the raw ConfigMap data values.
+
+<!--mdtogo:Long-->
+
+## Usage
+
+To use this function, define a GenConfigMap resource for each ConfigMap you want
+to generate. It can be used declaratively or imperatively, but it does require
+the GenConfigMap Kind; you cannot run it using a simple ConfigMap for inputs.
+
+When run, it will create or overwrite a ConfigMap, and generate `data` field
+entries for each of the listed values in the function config.
+
+### FunctionConfig
+
+```yaml
+apiVersion: fn.kpt.dev/v1alpha1
+kind: GenConfigMap
+metadata:
+  name: my-generator
+configMapMetadata:
+  name: my-configmap
+  labels:
+    foo: bar
+params:
+  hostname: foo.example.com
+  port: 8992
+  scheme: https
+  region: us-east1
+data:
+- type: literal
+  key: hello
+  value: there
+- type: gotmpl
+  key: dburl
+  value: "{{.scheme}}://{{.hostname}}:{{.port}}/{{.region}}/db"
+```
+
+The function config above will generate the following ConfigMap:
+
+```yaml
+kind: ConfigMap
+metadata:
+  name: my-configmap
+   labels:
+    foo: bar
+data:
+  dburl: https://foo.example.com:8992/us-east1/db
+  hello: there
+```
+
+If `configMapMetadata.name` is not defined, the generated ConfigMap will use the
+name of the GenConfigMap resource.
+
+<!--mdtogo-->
+
+## Future Work
+
+This function is very basic right now. Integration with CEL and implementation
+of features found in the Kustomize ConfigMapGenerator would be valuable.

krm-functions/gen-configmap-fn/fn/gen_configmap.go

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+/*
+Copyright 2023 Nephio.
+
+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 fn
+
+import (
+	"bytes"
+	"fmt"
+	"text/template"
+
+	"github.com/GoogleContainerTools/kpt-functions-sdk/go/fn"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
+
+	"sigs.k8s.io/kustomize/kyaml/kio/kioutil"
+)
+
+type GenConfigMapEntry struct {
+	Type  string
+	Key   string
+	Value string
+}
+
+type GenConfigMap struct {
+	ConfigMapMetadata metav1.ObjectMeta
+	Params            map[string]string
+	Data              []GenConfigMapEntry
+}
+
+func (entry *GenConfigMapEntry) generate(params, data map[string]string) error {
+	switch entry.Type {
+	case "gotmpl":
+		t, err := template.New(entry.Key).Parse(entry.Value)
+		if err != nil {
+			return err
+		}
+		buf := &bytes.Buffer{}
+		err = t.Execute(buf, params)
+		if err != nil {
+			return err
+		}
+		data[entry.Key] = buf.String()
+	default:
+		data[entry.Key] = entry.Value
+	}
+
+	return nil
+}
+
+func (fc *GenConfigMap) Validate() error {
+	for i, entry := range fc.Data {
+		if entry.Key == "" {
+			return fmt.Errorf("data entry %d, key must not be empty", i)
+		}
+	}
+	return nil
+}
+
+func Process(rl *fn.ResourceList) (bool, error) {
+	// read our fc into a new struct
+	fc := &GenConfigMap{}
+	err := rl.FunctionConfig.As(fc)
+	if err != nil {
+		return false, err
+	}
+
+	name := fc.ConfigMapMetadata.Name
+	if name == "" {
+		name = rl.FunctionConfig.GetName()
+	}
+
+	err = fc.Validate()
+	if err != nil {
+		return false, err
+	}
+
+	cmko := fn.NewEmptyKubeObject()
+	err = cmko.SetAPIVersion("v1")
+	if err != nil {
+		return false, err
+	}
+	err = cmko.SetKind("ConfigMap")
+	if err != nil {
+		return false, err
+	}
+	err = cmko.SetNestedField(fc.ConfigMapMetadata, "metadata")
+	if err != nil {
+		return false, err
+	}
+	_, err = cmko.RemoveNestedField("metadata", "creationTimestamp")
+	if err != nil {
+		return false, err
+	}
+	err = cmko.SetName(name)
+	if err != nil {
+		return false, err
+	}
+
+	err = cmko.SetAnnotation(kioutil.PathAnnotation, "_gen_configmap_"+name+".yaml")
+	if err != nil {
+		return false, err
+	}
+
+	data := make(map[string]string, len(fc.Data))
+	for i, entry := range fc.Data {
+		err = entry.generate(fc.Params, data)
+		if err != nil {
+			return false, fmt.Errorf("data entry %d generate error: %s", i, err.Error())
+		}
+	}
+	if len(data) > 0 {
+		err = cmko.SetNestedField(data, "data")
+		if err != nil {
+			return false, err
+		}
+	}
+	err = rl.UpsertObjectToItems(cmko, nil, true)
+	if err != nil {
+		return false, err
+	}
+
+	return true, nil
+}

krm-functions/gen-configmap-fn/fn/gen_configmap_test.go

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+/*
+Copyright 2023 Nephio.
+
+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 fn
+
+import (
+	"github.com/GoogleContainerTools/kpt-functions-sdk/go/fn"
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+
+func TestErrorCases(t *testing.T) {
+	cases := map[string]struct {
+		input       []byte
+		errExpected string
+	}{
+		"MissingKey": {
+			input: []byte(`
+apiVersion: fn.kpt.dev/v1alpha1
+kind: GenConfigMap
+metadata:
+  name: empty-test
+data:
+- type: literal
+  value: foo`),
+			errExpected: "data entry 0, key must not be empty",
+		},
+		"GoTemplateParseError": {
+			input: []byte(`
+apiVersion: fn.kpt.dev/v1alpha1
+kind: GenConfigMap
+metadata:
+  name: empty-test
+data:
+- type: gotmpl
+  key: bad
+  value: foo{{`),
+			errExpected: "data entry 0 generate error: template: bad:1: unclosed action",
+		},
+		"GoTemplateExecuteError": {
+			input: []byte(`
+apiVersion: fn.kpt.dev/v1alpha1
+kind: GenConfigMap
+metadata:
+  name: empty-test
+data:
+- type: gotmpl
+  key: bad
+  value: foo{{template "nope"}}`),
+			errExpected: "data entry 0 generate error: template: bad:1:14: executing \"bad\" at <{{template \"nope\"}}>: template \"nope\" not defined",
+		},
+	}
+
+	for name, tc := range cases {
+		t.Run(name, func(t *testing.T) {
+			ko, err := fn.ParseKubeObject(tc.input)
+			assert.NoError(t, err)
+
+			_, err = Process(&fn.ResourceList{FunctionConfig: ko})
+			if tc.errExpected != "" {
+				assert.EqualError(t, err, tc.errExpected)
+			} else {
+				assert.NoError(t, err)
+			}
+		})
+	}
+}

krm-functions/gen-configmap-fn/fn/golden_test.go

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+/*
+ Copyright 2023 The Nephio 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 fn
+
+import (
+	"testing"
+
+	"github.com/GoogleContainerTools/kpt-functions-sdk/go/fn"
+	"github.com/GoogleContainerTools/kpt-functions-sdk/go/fn/testhelpers"
+)
+
+const TestDataPath = "testdata"
+
+func TestFunction(t *testing.T) {
+	// This golden test expects each sub-directory of `testdata` can has its input resources (in `resources.yaml`)
+	// be modified to the output resources (in `_expected.yaml`).
+	testhelpers.RunGoldenTests(t, TestDataPath, fn.ResourceListProcessorFunc(Process))
+}

krm-functions/gen-configmap-fn/fn/testdata/empty/_expected.yaml

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+apiVersion: config.kubernetes.io/v1
+kind: ResourceList
+items:
+- apiVersion: v1
+  kind: ConfigMap
+  metadata:
+    name: empty-test
+    annotations:
+      internal.config.kubernetes.io/path: _gen_configmap_empty-test.yaml
+functionConfig:
+  apiVersion: fn.kpt.dev/v1alpha1
+  kind: GenConfigMap
+  metadata:
+    name: empty-test

krm-functions/gen-configmap-fn/fn/testdata/empty/_fnconfig.yaml

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+apiVersion: fn.kpt.dev/v1alpha1
+kind: GenConfigMap
+metadata:
+  name: empty-test