Support --tags for YAML tag files.

Makefile

@@ -2,7 +2,7 @@ PACKAGE = github.com/cultureamp/cfparams
 VERSION = $(shell git describe --tags --candidates=1 --dirty)
 FLAGS=-X main.Version=$(VERSION) -s -w
 
-cfparams: main.go parameters.go template.go parameterstore/store.go
+cfparams: main.go parameters.go tags.go template.go parameterstore/store.go
 	go build -ldflags="$(FLAGS)"
 
 .PHONY: install

README.md

@@ -190,3 +190,44 @@ Resulting JSON:
   {"ParameterKey": "Cluster", "ParameterValue": "staging"}
 ]
 ```
+
+### Bonus feature: Stack Tags
+
+CloudFormation stacks can be tagged, and those tags flow into all taggable
+resources the stack creates. As with `--parameters`, the `aws cloudformation`
+commands expect these in an awkward format. `cfparams --tags file.yaml` helps.
+
+```sh
+aws cloudformation create-stack \
+  ... \
+  --tags "$(cfparams --tags=tags-production.yaml)" \
+  ...
+```
+
+```yaml
+# tags-production.yaml
+Name: Widgets as a Service
+asset: widget-api
+workload: production
+```
+
+```sh
+cfparams --tags=tags-production.yaml
+```
+
+```json
+[
+  {
+    "Key": "Name",
+    "Value": "Widgets as a Service"
+  },
+  {
+    "Key": "asset",
+    "Value": "widget-api"
+  },
+  {
+    "Key": "workload",
+    "Value": "production"
+  }
+]
+```

example/tags-production.yaml

@@ -0,0 +1,3 @@
+Name: Widgets as a Service
+asset: widget-api
+workload: production

main.go

@@ -12,6 +12,7 @@ var Version = "dev"
 
 type Input struct {
 	TemplateBody   []byte
+	TagsBody       []byte
 	AcceptDefaults bool
 	NoPrevious     bool
 	ParametersCLI  []string
@@ -21,7 +22,7 @@ type Input struct {
 
 func main() {
 	input := &Input{}
-	var tplFile, paramFile string
+	var tplFile, paramFile, tagFile string
 
 	flag.Usage = func() {
 		fmt.Fprintf(os.Stderr, "cfparams %s\n\n", Version)
@@ -31,19 +32,29 @@ func main() {
 	}
 	flag.StringVar(&tplFile, "template", "", "CloudFormation YAML template path")
 	flag.StringVar(&paramFile, "parameters", "", "Parameters YAML file")
+	flag.StringVar(&tagFile, "tags", "", "Tags YAML file")
 	flag.BoolVar(&input.AcceptDefaults, "accept-defaults", false, "Accept defaults from CloudFormation template, omit from JSON")
 	flag.BoolVar(&input.NoPrevious, "no-previous", false, "Disable UsePreviousValue, fail if a parameter has no default and is not specified")
 	flag.Parse()
 
-	if tplFile != "" {
+	if tagFile != "" {
+		data, err := ioutil.ReadFile(tagFile)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "cannot read tags file: %s\n", tplFile)
+			os.Exit(1)
+		}
+		input.TagsBody = data
+	} else if tplFile != "" {
 		data, err := ioutil.ReadFile(tplFile)
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "cannot read CloudFormation template: %s\n", tplFile)
 			os.Exit(1)
 		}
 		input.TemplateBody = data
 	} else {
-		fmt.Fprintf(os.Stderr, "CloudFormation template required, e.g: --template=cfn.yaml\n")
+		fmt.Fprintf(os.Stderr, "CloudFormation template or tags file required\n")
+		fmt.Fprintf(os.Stderr, "    e.g: --template=cloudformation.yaml\n")
+		fmt.Fprintf(os.Stderr, "    e.g: --tags=tags-foo.yaml\n")
 		os.Exit(1)
 	}
 
@@ -70,5 +81,9 @@ func main() {
 }
 
 func getJsonForInput(input *Input) ([]byte, error) {
-	return getJsonForInputParams(input) // parameters.go
+	if len(input.TagsBody) > 0 {
+		return getJsonForInputTags(input) // tags.go
+	} else {
+		return getJsonForInputParams(input) // parameters.go
+	}
 }

main_test.go

@@ -165,6 +165,24 @@ func TestCustomYamlTags(t *testing.T) {
 	require.Equal(t, false, item.UsePreviousValue)
 }
 
+func TestTags(t *testing.T) {
+	input := &Input{
+		TagsBody: []byte("Foo: 1\nBar: two\n"),
+	}
+	j, err := getJsonForInput(input)
+	require.NoError(t, err)
+	type tagItem struct {
+		Key   string
+		Value string
+	}
+	var items []tagItem
+	err = json.Unmarshal(j, &items)
+	require.ElementsMatch(t, []tagItem{
+		{Key: "Foo", Value: "1"},
+		{Key: "Bar", Value: "two"},
+	}, items)
+}
+
 func mustGetJson(t *testing.T, input *Input) string {
 	j, err := getJsonForInput(input)
 	require.NoError(t, err)

tags.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"encoding/json"
+
+	yaml "github.com/sanathkr/go-yaml"
+)
+
+type jsonItem struct {
+	Key   string
+	Value string
+}
+
+func getJsonForInputTags(input *Input) ([]byte, error) {
+	data := map[string]string{}
+	yaml.Unmarshal(input.TagsBody, &data)
+	items := []jsonItem{}
+	for key, value := range data {
+		items = append(items, jsonItem{Key: key, Value: value})
+	}
+	for key, value := range input.Parameters {
+		items = append(items, jsonItem{Key: key, Value: value})
+	}
+	return json.MarshalIndent(items, "", "  ")
+}