One plugin per dir.

plugin/someteam.example.com/v1/chartinflator/ChartInflator

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+#!/bin/bash
+# Copyright 2019 The Kubernetes Authors.
+# SPDX-License-Identifier: Apache-2.0
+
+# Helm chart inflator
+#
+# Reads a file like this
+#
+#  apiVersion: kustomize.config.k8s.io/v1
+#  kind: ChartInflator
+#  metadata:
+#    name: notImportantHere
+#  chartName: nameOfStableChart
+#  values: /abs/path/to/local/values/file
+#  chartHome: /abs/path/local/chart/storage
+#  helmHome: /abs/path/to/helm/config
+#  helmBin: /abs/path/to/helmBin
+#
+# fetches the given chart from stable/$chartName,
+# and inflates it to stdout, using the given values file.
+#
+# chartDir default: $TMP_DIR/charts
+#
+# Example execution:
+# ./plugin/someteam.example.com/v1/ChartInflator configFile.yaml
+
+set -e
+
+# Yaml parsing is a ridiculous thing to do in bash,
+# but let's try:
+function parseYaml {
+  local file=$1
+  while read -r line
+  do
+    local k=${line%:*}
+    local v=${line#*:}
+
+    [ "$k" == "chartName" ] && chartName=$v
+    [ "$k" == "chartHome" ] && chartHome=$v
+    [ "$k" == "values" ] && valuesFile=$v
+    [ "$k" == "helmHome" ] && helmHome=$v
+    [ "$k" == "helmBin" ] && helmBin=$v
+  done <"$file"
+
+  # Trim leading space
+  chartName="${chartName#"${chartName%%[![:space:]]*}"}"
+  chartHome="${chartHome#"${chartHome%%[![:space:]]*}"}"
+  valuesFile="${valuesFile#"${valuesFile%%[![:space:]]*}"}"
+  helmBin="${helmBin#"${helmBin%%[![:space:]]*}"}"
+}
+
+TMP_DIR=$(mktemp -d)
+
+parseYaml $1
+
+# Where all the files generated by 'helm init' live.
+if [ -z "$helmHome" ]; then
+  helmHome=$TMP_DIR/dotHelm
+fi
+
+# Where helm charts are unpacked.
+if [ -z "$chartHome" ]; then
+  chartHome=$TMP_DIR/charts
+fi
+
+if [ -z "$helmBin" ]; then
+  helmBin=helm
+fi
+
+if [ -z "$valuesFile" ]; then
+  valuesFile=$chartHome/$chartName/values.yaml
+fi
+
+function doHelm {
+  $helmBin --home $helmHome $@
+}
+
+# The init command is extremely chatty
+doHelm init --client-only >& /dev/null
+
+if [ ! -d "$chartHome/$chartName" ]; then
+  doHelm fetch --untar \
+      --untardir $chartHome \
+      stable/$chartName
+fi
+
+doHelm template \
+    --values $valuesFile \
+    $chartHome/$chartName
+
+/bin/rm -rf $TMP_DIR

plugin/someteam.example.com/v1/chartinflator/ChartInflator_test.go

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+// +build notravis
+
+// Copyright 2019 The Kubernetes Authors.
+// SPDX-License-Identifier: Apache-2.0
+
+// Disabled on travis, because don't want to install helm on travis.
+
+package main_test
+
+import (
+	"testing"
+
+	"sigs.k8s.io/kustomize/pkg/kusttest"
+	"sigs.k8s.io/kustomize/plugin"
+)
+
+// This test requires having the helm binary on the PATH.
+//
+// TODO: Download and inflate the chart, and check that
+// in for the test.
+func TestChartInflator(t *testing.T) {
+	tc := plugin.NewEnvForTest(t).Set()
+	defer tc.Reset()
+
+	tc.BuildExecPlugin(
+		"someteam.example.com", "v1", "ChartInflator")
+
+	th := kusttest_test.NewKustTestPluginHarness(t, "/app")
+
+	m := th.LoadAndRunGenerator(`
+apiVersion: someteam.example.com/v1
+kind: ChartInflator
+metadata:
+  name: notImportantHere
+chartName: minecraft`)
+
+	th.AssertActualEqualsExpected(m, `
+apiVersion: v1
+data:
+  rcon-password: Q0hBTkdFTUUh
+kind: Secret
+metadata:
+  labels:
+    app: release-name-minecraft
+    chart: minecraft-1.0.0
+    heritage: Tiller
+    release: release-name
+  name: release-name-minecraft
+type: Opaque
+---
+apiVersion: v1
+kind: Service
+metadata:
+  labels:
+    app: release-name-minecraft
+    chart: minecraft-1.0.0
+    heritage: Tiller
+    release: release-name
+  name: release-name-minecraft
+spec:
+  ports:
+  - name: minecraft
+    port: 25565
+    protocol: TCP
+    targetPort: minecraft
+  selector:
+    app: release-name-minecraft
+  type: LoadBalancer
+---
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  annotations:
+    volume.alpha.kubernetes.io/storage-class: default
+  labels:
+    app: release-name-minecraft
+    chart: minecraft-1.0.0
+    heritage: Tiller
+    release: release-name
+  name: release-name-minecraft-datadir
+spec:
+  accessModes:
+  - ReadWriteOnce
+  resources:
+    requests:
+      storage: 1Gi
+`)
+}