feat: JSON output

This adds the JSON output on top of #221, which can be enabled by passing `--output json`. Internally it works exactly the same as the `template` output format with the default template.

```
********************

        Release was not present in Helm.  Diff will show entire contents as new.

********************
[{
  "api": "v1",
  "kind": "Secret",
  "namespace": "default",
  "name": "mysql-1567775891",
  "change": "ADD"
},{
  "api": "v1",
  "kind": "ConfigMap",
  "namespace": "default",
  "name": "mysql-1567775891-test",
  "change": "ADD"
},{
  "api": "v1",
  "kind": "PersistentVolumeClaim",
  "namespace": "default",
  "name": "mysql-1567775891",
  "change": "ADD"
},{
  "api": "v1",
  "kind": "Service",
  "namespace": "default",
  "name": "mysql-1567775891",
  "change": "ADD"
},{
  "api": "apps",
  "kind": "Deployment",
  "namespace": "default",
  "name": "mysql-1567775891",
  "change": "ADD"
}]
```

Ref #221 (review)

Author: mumoshu

Makefile

@@ -5,13 +5,13 @@ PKG:= github.com/databus23/helm-diff
 LDFLAGS := -X $(PKG)/cmd.Version=$(VERSION)
 
 # Clear the "unreleased" string in BuildMetadata
-LDFLAGS += -X $(PKG)/vendor/k8s.io/helm/pkg/version.BuildMetadata=
-LDFLAGS += -X $(PKG)/vendor/k8s.io/helm/pkg/version.Version=$(shell grep -A1 "package: k8s.io/helm" go.mod | sed -n -e 's/[ ]*version:.*\(v[.0-9]*\).*/\1/p')
+LDFLAGS += -X k8s.io/helm/pkg/version.BuildMetadata=
+LDFLAGS += -X k8s.io/helm/pkg/version.Version=$(shell ./scripts/dep-helm-version.sh)
 
 .PHONY: format
 format:
-	test -z "$$(find . -path ./vendor -prune -type f -o -name '*.go' -exec gofmt -d {} + | tee /dev/stderr)" || \
-	test -z "$$(find . -path ./vendor -prune -type f -o -name '*.go' -exec gofmt -w {} + | tee /dev/stderr)"
+	test -z "$$(find . -type f -o -name '*.go' -exec gofmt -d {} + | tee /dev/stderr)" || \
+	test -z "$$(find . -type f -o -name '*.go' -exec gofmt -w {} + | tee /dev/stderr)"
 
 .PHONY: install
 install: build

cmd/upgrade.go

@@ -112,7 +112,7 @@ func newChartCommand() *cobra.Command {
 	f.IntVarP(&diff.outputContext, "context", "C", -1, "output NUM lines of context around changes")
 	f.BoolVar(&diff.disableOpenAPIValidation, "disable-openapi-validation", false, "disables rendered templates validation against the Kubernetes OpenAPI Schema")
 	f.StringVar(&diff.postRenderer, "post-renderer", "", "the path to an executable to be used for post rendering. If it exists in $PATH, the binary will be used, otherwise it will try to look for the executable at the given path")
-	f.StringVar(&diff.output, "output", "diff", "Possible values: diff, simple, template. When set to \"template\", use the env var HELM_DIFF_TPL to specify the template.")
+	f.StringVar(&diff.output, "output", "diff", "Possible values: diff, simple, json, template. When set to \"template\", use the env var HELM_DIFF_TPL to specify the template.")
 	if !isHelm3() {
 		f.StringVar(&diff.namespace, "namespace", "default", "namespace to assume the release to be installed into")
 	}

diff/constant.go

@@ -4,10 +4,11 @@ const defaultTemplateReport = `[
 {{- $global := . -}}
 {{- range $idx, $entry := . -}}
 {
-  "Api": "{{ $entry.API }}",
-  "Kind": "{{ $entry.Kind }}",
-  "Namespace": "{{ $entry.Namespace }}",
-  "Name": "{{ $entry.Name }}",
-  "Change": "{{ $entry.Change }}"
+  "api": "{{ $entry.API }}",
+  "kind": "{{ $entry.Kind }}",
+  "namespace": "{{ $entry.Namespace }}",
+  "name": "{{ $entry.Name }}",
+  "change": "{{ $entry.Change }}"
 }{{ if not (last $idx  $global) }},{{ end }}
-{{- end }}]`
+{{- end }}]
+`

diff/report.go

@@ -33,7 +33,7 @@ type ReportEntry struct {
 
 // ReportFormat to the context to make a changes report
 type ReportFormat struct {
-	output       string
+	output       func(r *Report, to io.Writer)
 	changestyles map[string]ChangeStyle
 }
 
@@ -61,6 +61,8 @@ func (r *Report) setupReportFormat(format string) {
 		setupSimpleReport(&report)
 	case "template":
 		setupTemplateReport(&report)
+	case "json":
+		setupJSONReport(&report)
 	default:
 		setupDiffReport(&report)
 	}
@@ -81,14 +83,7 @@ func (r *Report) addEntry(key string, suppressedKinds []string, kind string, con
 
 // print: prints entries added to the report.
 func (r *Report) print(to io.Writer) {
-	switch r.format.output {
-	case "simple":
-		printSimpleReport(r, to)
-	case "template":
-		printTemplateReport(r, to)
-	default:
-		printDiffReport(r, to)
-	}
+	r.format.output(r, to)
 }
 
 // clean: needed for testing
@@ -98,7 +93,7 @@ func (r *Report) clean() {
 
 // setup report for default output: diff
 func setupDiffReport(r *Report) {
-	r.format.output = "diff"
+	r.format.output = printDiffReport
 	r.format.changestyles = make(map[string]ChangeStyle)
 	r.format.changestyles["ADD"] = ChangeStyle{color: "green", message: "has been added:"}
 	r.format.changestyles["REMOVE"] = ChangeStyle{color: "red", message: "has been removed:"}
@@ -116,7 +111,7 @@ func printDiffReport(r *Report, to io.Writer) {
 
 // setup report for simple output.
 func setupSimpleReport(r *Report) {
-	r.format.output = "simple"
+	r.format.output = printSimpleReport
 	r.format.changestyles = make(map[string]ChangeStyle)
 	r.format.changestyles["ADD"] = ChangeStyle{color: "green", message: "to be added."}
 	r.format.changestyles["REMOVE"] = ChangeStyle{color: "red", message: "to be removed."}
@@ -140,9 +135,55 @@ func printSimpleReport(r *Report, to io.Writer) {
 	fmt.Fprintf(to, "Plan: %d to add, %d to change, %d to destroy.\n", summary["ADD"], summary["MODIFY"], summary["REMOVE"])
 }
 
+func newTemplate(name string) *template.Template {
+	// Prepare template functions
+	var funcsMap = template.FuncMap{
+		"last": func(x int, a interface{}) bool {
+			return x == reflect.ValueOf(a).Len()-1
+		},
+	}
+
+	return template.New(name).Funcs(funcsMap)
+}
+
+// setup report for json output
+func setupJSONReport(r *Report) {
+	t, err := newTemplate("entries").Parse(defaultTemplateReport)
+	if err != nil {
+		log.Fatalf("Error loadding default template: %w", err)
+	}
+
+	r.format.output = templateReportPrinter(t)
+	r.format.changestyles = make(map[string]ChangeStyle)
+	r.format.changestyles["ADD"] = ChangeStyle{color: "green", message: ""}
+	r.format.changestyles["REMOVE"] = ChangeStyle{color: "red", message: ""}
+	r.format.changestyles["MODIFY"] = ChangeStyle{color: "yellow", message: ""}
+}
+
 // setup report for template output
 func setupTemplateReport(r *Report) {
-	r.format.output = "template"
+	var tpl *template.Template
+
+	{
+		tplFile, present := os.LookupEnv("HELM_DIFF_TPL")
+		if present {
+			t, err := newTemplate(filepath.Base(tplFile)).ParseFiles(tplFile)
+			if err != nil {
+				fmt.Println(err)
+				log.Fatalf("Error loadding custom template")
+			}
+			tpl = t
+		} else {
+			// Render
+			t, err := newTemplate("entries").Parse(defaultTemplateReport)
+			if err != nil {
+				log.Fatalf("Error loadding default template")
+			}
+			tpl = t
+		}
+	}
+
+	r.format.output = templateReportPrinter(tpl)
 	r.format.changestyles = make(map[string]ChangeStyle)
 	r.format.changestyles["ADD"] = ChangeStyle{color: "green", message: ""}
 	r.format.changestyles["REMOVE"] = ChangeStyle{color: "red", message: ""}
@@ -165,42 +206,21 @@ func (t *ReportTemplateSpec) loadFromKey(key string) error {
 }
 
 // load and print report for template output
-func printTemplateReport(r *Report, to io.Writer) {
-	var templateDataArray []ReportTemplateSpec
-
-	for _, entry := range r.entries {
-		templateData := ReportTemplateSpec{}
-		err := templateData.loadFromKey(entry.key)
-		if err != nil {
-			log.Println("error processing report entry")
-		} else {
-			templateData.Change = entry.changeType
-			templateDataArray = append(templateDataArray, templateData)
+func templateReportPrinter(t *template.Template) func(r *Report, to io.Writer) {
+	return func(r *Report, to io.Writer) {
+		var templateDataArray []ReportTemplateSpec
+
+		for _, entry := range r.entries {
+			templateData := ReportTemplateSpec{}
+			err := templateData.loadFromKey(entry.key)
+			if err != nil {
+				log.Println("error processing report entry")
+			} else {
+				templateData.Change = entry.changeType
+				templateDataArray = append(templateDataArray, templateData)
+			}
 		}
-	}
 
-	// Prepare template functions
-	var funcsMap = template.FuncMap{
-		"last": func(x int, a interface{}) bool {
-			return x == reflect.ValueOf(a).Len()-1
-		},
-	}
-
-	tplFile, present := os.LookupEnv("HELM_DIFF_TPL")
-	if present {
-		t, err := template.New(filepath.Base(tplFile)).Funcs(funcsMap).ParseFiles(tplFile)
-		if err != nil {
-			fmt.Println(err)
-			log.Fatalf("Error loadding custom template")
-		}
 		t.Execute(to, templateDataArray)
-	} else {
-		// Render
-		t, err := template.New("entries").Funcs(funcsMap).Parse(defaultTemplateReport)
-		if err != nil {
-			log.Fatalf("Error loadding default template")
-		} else {
-			t.Execute(to, templateDataArray)
-		}
 	}
 }