An example of the injection mutation function

Mutate.ts

import * as jsonpatch from 'fast-json-patch';

const mutate = (admissionReviewRequest: V1AdmissionRequest<V1Pod>): V1AdmissionResponse => {
  const admissionReviewResponse: V1AdmissionResponse = {
    allowed: true,
    uid: admissionReviewRequest.uid,
  };

  // get the pod object and clone it
  const originalPod = admissionReviewRequest.object as V1Pod;
  const mutatedPod = JSON.parse(JSON.stringify(originalPod)) as V1Pod;

  // update the mutated pod spec with the new containers array
  const mutatedPodContainers = injectContainer(originalPod.spec?.containers);
  mutatedPod.spec = { ...mutatedPod.spec, containers: mutatedPodContainers };

  // generate json patch string
  const patchArray = jsonpatch.compare(originalPod, mutatedPod);
  const patchArrayJsonStr = JSON.stringify(patchArray);

  admissionReviewResponse.patchType = "JSONPatch";
  admissionReviewResponse.patch = Buffer.from(patchArrayJsonStr).toString('base64');

  return admissionReviewResponse;
}

const injectContainer = (containers: V1Container[] = []): V1Container[] => {
  const sidecarContainer: V1Container = {
    name: 'curl',
    image: 'yauritux/busybox-curl:latest'
  };

  return [...containers, sidecarContainer];
};