feat(kaniko): pass extraFlags to kaniko builders

This means we can use extra features from kaniko.
The default behaviour is to try and merge the args

garden-service/src/plugins/kubernetes/container/build.ts

@@ -8,6 +8,7 @@
 
 import pRetry from "p-retry"
 import split2 = require("split2")
+import { differenceBy } from "lodash"
 import { ContainerModule, ContainerRegistryConfig } from "../../container/config"
 import { containerHelpers } from "../../container/helpers"
 import { buildContainerModule, getContainerBuildStatus, getDockerBuildFlags } from "../../container/build"
@@ -336,7 +337,7 @@ const remoteBuild: BuildHandler = async (params) => {
       dockerfile,
       "--destination",
       deploymentImageId,
-      "--cache=true",
+      ...getKanikoFlags(module.spec.extraFlags),
     ]
 
     if (provider.config.deploymentRegistry?.hostname === inClusterRegistryHostname) {
@@ -380,6 +381,24 @@ export interface BuilderExecParams {
   stderr?: Writable
 }
 
+export const DEFAULT_KANIKO_FLAGS = ["--cache=true"]
+
+export const getKanikoFlags = (flags?: string[]): string[] => {
+  if (!flags) {
+    return DEFAULT_KANIKO_FLAGS
+  }
+  const flagToKey = (flag) => {
+    const found = flag.match(/--([a-zA-Z]*)/)
+    if (found === null) {
+      throw new ConfigurationError(`Invalid format for a kaniko flag`, { flag })
+    }
+    return found[0]
+  }
+  const defaultsToKeep = differenceBy(DEFAULT_KANIKO_FLAGS, flags, flagToKey)
+
+  return [...flags, ...defaultsToKeep]
+}
+
 export function kanikoBuildFailed(buildRes: RunResult) {
   return !buildRes.success && !buildRes.log.includes("cannot be overwritten because the repository is immutable.")
 }

garden-service/test/unit/src/plugins/kubernetes/container/build.ts

@@ -6,12 +6,16 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
  */
 
-import { kanikoBuildFailed } from "../../../../../../src/plugins/kubernetes/container/build"
+import {
+  kanikoBuildFailed,
+  getKanikoFlags,
+  DEFAULT_KANIKO_FLAGS,
+} from "../../../../../../src/plugins/kubernetes/container/build"
 import { expect } from "chai"
 
 describe("kaniko build", () => {
   it("should return as successful when immutable tag already exists in destination", () => {
-    const errorMessage = `error pushing image: failed to push to destination dockerhub.com/garden/backend:v-1234567: TAG_INVALID: The image tag 'v-1234567' already exists in the 'garden/backend' repository and cannot be overwritten because the repository is immutable.`
+    const errorMessage = `error pushing image: failed to push to destination dockerhub.com/garden/backend:v-1234567: TAG_INVALID: The image tag "v-1234567" already exists in the "garden/backend" repository and cannot be overwritten because the repository is immutable.`
 
     expect(
       kanikoBuildFailed({
@@ -55,4 +59,31 @@ describe("kaniko build", () => {
       })
     ).to.be.false
   })
+
+  describe("getKanikoFlags", () => {
+    it("should only keep all declarations of each flag + the defaults", () => {
+      expect(getKanikoFlags(["--here=first", "--here=again"])).to.deep.equal([
+        "--here=first",
+        "--here=again",
+        "--cache=true",
+      ])
+    })
+    it("should allow overriding default flags", () => {
+      const overridenFlags = DEFAULT_KANIKO_FLAGS.map((f) => f + "cat")
+      expect(getKanikoFlags(overridenFlags)).to.deep.equal(overridenFlags)
+    })
+
+    it("should allow toggles", () => {
+      expect(getKanikoFlags(["--myToggle"])).to.deep.equal(["--myToggle", "--cache=true"])
+    })
+
+    it("should throw if a flag is malformed", () => {
+      expect(() => getKanikoFlags(["--here=first", "-my-flag"])).to.throw(/Invalid format for a kaniko flag/)
+    })
+
+    it("should return --cache=true when extraFlags is empty", () => {
+      expect(getKanikoFlags([])).to.deep.equal(DEFAULT_KANIKO_FLAGS)
+      expect(getKanikoFlags()).to.deep.equal(DEFAULT_KANIKO_FLAGS)
+    })
+  })
 })