Use the stable directory for storing temporary charts and values files

so that helmfile-diff output becomes stables and terraform plan doesn't break.
See roboll/helmfile#1622 for more information.

go.mod

@@ -4,6 +4,7 @@ go 1.13
 
 require (
 	github.com/Masterminds/semver v1.5.0
+	github.com/davecgh/go-spew v1.1.1
 	github.com/hashicorp/terraform-plugin-sdk v1.0.0
 	github.com/mitchellh/go-linereader v0.0.0-20190213213312-1b945b3263eb
 	github.com/mumoshu/shoal v0.2.14

pkg/helmfile/hash.go

@@ -0,0 +1,25 @@
+package helmfile
+
+import (
+	"fmt"
+	"github.com/davecgh/go-spew/spew"
+	"hash/fnv"
+)
+
+func HashObject(obj interface{}) (string, error) {
+	hash := fnv.New32a()
+
+	hash.Reset()
+
+	printer := spew.ConfigState{
+		Indent:         " ",
+		SortKeys:       true,
+		DisableMethods: true,
+		SpewKeys:       true,
+	}
+	printer.Fprintf(hash, "%#v", obj)
+
+	sum := fmt.Sprint(hash.Sum32())
+
+	return SafeEncodeString(sum), nil
+}

pkg/helmfile/release_set.go

@@ -448,6 +448,30 @@ func runDiff(fs *ReleaseSet, conf DiffConfig) (*State, error) {
 		return nil, err
 	}
 
+	// Use the stable directory for storing temporary charts and values files
+	// so that helmfile-diff output becomes stables and terraform plan doesn't break.
+	// See https://github.com/roboll/helmfile/pull/1622
+
+	hash, err := HashObject(fs)
+	if err != nil {
+		return nil, xerrors.Errorf("computing hash of object: %w", err)
+	}
+
+	tempDir := filepath.Join(".terraform", "helmfile", fmt.Sprintf("temp-%s", hash))
+
+	if info, _ := os.Stat(tempDir); info != nil {
+		if err := os.RemoveAll(tempDir); err != nil {
+			return nil, xerrors.Errorf("removing stable temp directory %s: %w", tempDir, err)
+		}
+	}
+
+	if err := os.MkdirAll(tempDir, 0755); err != nil {
+		return nil, xerrors.Errorf("creating temp directory for helmfile and chartify %s: %w", tempDir, err)
+	}
+
+	cmd.Env = append(cmd.Env, "HELMFILE_TEMPDIR="+tempDir)
+	cmd.Env = append(cmd.Env, "CHARTIFY_TEMPDIR="+tempDir)
+
 	if conf.Kubeconfig != "" {
 		cmd.Env = append(cmd.Env, "KUBECONFIG="+conf.Kubeconfig)
 	}

pkg/helmfile/safe_encode_string.go

@@ -0,0 +1,30 @@
+/*
+Copyright 2015 The Kubernetes 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.
+*/
+// See k8s.io/apimachinery/pkg/util/rand/rand.go
+package helmfile
+
+const (
+	// We omit vowels from the set of available characters to reduce the chances
+	// of "bad words" being formed.
+	alphanums = "bcdfghjklmnpqrstvwxz2456789"
+)
+
+// SafeEncodeString encodes s using the same characters as rand.String. This reduces the chances of bad words and
+// ensures that strings generated from hash functions appear consistent throughout the API.
+func SafeEncodeString(s string) string {
+	r := make([]byte, len(s))
+	for i, b := range []rune(s) {
+		r[i] = alphanums[(int(b) % len(alphanums))]
+	}
+	return string(r)
+}