Support helmfile template functions

README.md

@@ -225,6 +225,19 @@ docker run --rm -v "$PWD:/work" ghcr.io/digitalstudium/helmfmt:latest \
   --files templates/deployment.yaml templates/service.yaml
 ```
 
+### Helmfile templates
+
+[Helmfile](https://helmfile.readthedocs.io/) value files use extra template
+functions on top of Helm/Sprig (`env`, `requiredEnv`, `exec`, `readFile`,
+`fetchSecretValue`, ...). `helmfmt` accepts these functions as well, so it also
+formats helmfile files. The `.gotmpl` extension (e.g. `helmfile.yaml.gotmpl`,
+`values/demo.yaml.gotmpl`) is included by default:
+
+```bash
+helmfmt --check --files helmfile.yaml.gotmpl values/demo.yaml.gotmpl
+cat values/demo.yaml | helmfmt --check
+```
+
 ---
 
 ## Configuration
@@ -239,7 +252,7 @@ docker run --rm -v "$PWD:/work" ghcr.io/digitalstudium/helmfmt:latest \
 ```json
 {
   "indent_size": 2,
-  "extensions": [".yaml", ".yml", ".tpl"],
+  "extensions": [".yaml", ".yml", ".tpl", ".gotmpl"],
   "rules": {
     "indent": {
       "tpl": {

format.go

@@ -44,14 +44,16 @@ var (
 func stub(args ...interface{}) interface{} { return nil }
 
 // helmFuncMap returns a template.FuncMap containing stub registrations for
-// every sprig function (minus env/expandenv which Helm drops) plus Helm's own
-// additions. Only the presence of each name matters for parse-time syntax
-// validation; the stubs are never executed.
+// every sprig function (minus env/expandenv which Helm drops), Helm's own
+// additions, and the template functions helmfile registers on top of
+// Helm/Sprig (env, requiredEnv, exec, readFile, ...). Only the presence of
+// each name matters for parse-time syntax validation; the stubs are never
+// executed.
 //
 // The sprigStubNames slice is generated by `go generate` from the actual
 // sprig.TxtFuncMap(), so it stays in sync when sprig adds new functions.
 func helmFuncMap() template.FuncMap {
-	f := make(template.FuncMap, len(sprigStubNames)+10)
+	f := make(template.FuncMap, len(sprigStubNames)+25)
 	for _, name := range sprigStubNames {
 		f[name] = stub
 	}
@@ -64,18 +66,26 @@ func helmFuncMap() template.FuncMap {
 	for _, name := range helmExtras {
 		f[name] = stub
 	}
+	// Helmfile-specific functions not in Helm/sprig
+	helmfileExtras := []string{
+		"env", "requiredEnv", "exec", "envExec",
+		"readFile", "readDir", "readDirEntries",
+		"getOrNil", "setValueAtPath",
+		"fetchSecretValue", "expandSecretRefs", "kustomizeBuild",
+	}
+	for _, name := range helmfileExtras {
+		f[name] = stub
+	}
 	return f
 }
 
-// validateTemplateSyntax validates the given template source string using
-// Helm function set. Returns an error if the template has invalid syntax.
+// validateTemplateSyntax validates the given template source string using the
+// combined Helm/helmfile function set. Returns an error if the template has
+// invalid syntax.
 func validateTemplateSyntax(src string) error {
 
-	// Get Helm's built-in function map
-	helmFuncMap := helmFuncMap()
-
-	// Create and parse template with helm function map
-	_, err := template.New("validation").Funcs(helmFuncMap).Parse(src)
+	// Create and parse template with the function map
+	_, err := template.New("validation").Funcs(helmFuncMap()).Parse(src)
 	if err != nil {
 		return fmt.Errorf("invalid template syntax: %w", err)
 	}

main.go

@@ -37,7 +37,7 @@ func loadConfig() *Config {
 	// Default config
 	config := &Config{
 		IndentSize: 2,
-		Extensions: []string{".yaml", ".yml", ".tpl"},
+		Extensions: []string{".yaml", ".yml", ".tpl", ".gotmpl"},
 		Rules: RulesConfig{
 			Indent: map[string]RuleConfig{
 				"tpl":      {Disabled: true, Exclude: []string{}},

templates_test/helmfile_values.yaml

@@ -0,0 +1,3 @@
+name: "Helmfile .gotmpl values with env/requiredEnv"
+input_file: "templates/helmfile_values.yaml.gotmpl"
+expected_file: "templates_expected/helmfile_values.yaml.gotmpl"

templates_test/templates/helmfile_values.yaml.gotmpl

@@ -0,0 +1,7 @@
+{{- if env "FEATURE_ENABLED" }}
+{{ range $name := .Values.releases }}
+{{- $token := requiredEnv "GITHUB_TOKEN" }}
+name: {{ $name }}
+registry: {{ env "REGISTRY" | default "private.azurecr.io" }}
+{{- end }}
+{{- end }}

templates_test/templates_expected/helmfile_values.yaml.gotmpl

@@ -0,0 +1,7 @@
+{{- if env "FEATURE_ENABLED" }}
+  {{ range $name := .Values.releases }}
+    {{- $token := requiredEnv "GITHUB_TOKEN" }}
+name: {{ $name }}
+registry: {{ env "REGISTRY" | default "private.azurecr.io" }}
+  {{- end }}
+{{- end }}