Added implementation for a tpl function that evaluates a string as a template.

Implementation for #1978

pkg/engine/engine.go

@@ -64,7 +64,9 @@ func New() *Engine {
 //	- "include": This is late-bound in Engine.Render(). The version
 //	   included in the FuncMap is a placeholder.
 //      - "required": This is late-bound in Engine.Render(). The version
-//	   included in thhe FuncMap is a placeholder.
+//	   included in the FuncMap is a placeholder.
+//      - "tpl": This is late-bound in Engine.Render(). The version
+//	   included in the FuncMap is a placeholder.
 func FuncMap() template.FuncMap {
 	f := sprig.TxtFuncMap()
 	delete(f, "env")
@@ -83,6 +85,7 @@ func FuncMap() template.FuncMap {
 		// integrity of the linter.
 		"include":  func(string, interface{}) string { return "not implemented" },
 		"required": func(string, interface{}) interface{} { return "not implemented" },
+		"tpl":      func(string, interface{}) interface{} { return "not implemented" },
 	}
 
 	for k, v := range extra {
@@ -158,6 +161,23 @@ func (e *Engine) alterFuncMap(t *template.Template) template.FuncMap {
 		return val, nil
 	}
 
+	// Add the 'tpl' function here
+	funcMap["tpl"] = func(tpl string, vals chartutil.Values) string {
+		r := renderable{
+			tpl:  tpl,
+			vals: vals,
+		}
+
+		templates := map[string]renderable{}
+		templates["template"] = r
+
+		result, err := e.render(templates)
+		if err != nil {
+			return fmt.Errorf("Error during tpl function execution for %q", tpl).Error()
+		}
+		return result["template"]
+	}
+
 	return funcMap
 }
 

pkg/engine/engine_test.go

@@ -49,7 +49,7 @@ func TestFuncMap(t *testing.T) {
 	}
 
 	// Test for Engine-specific template functions.
-	expect := []string{"include", "required", "toYaml", "fromYaml", "toToml", "toJson", "fromJson"}
+	expect := []string{"include", "required", "tpl", "toYaml", "fromYaml", "toToml", "toJson", "fromJson"}
 	for _, f := range expect {
 		if _, ok := fns[f]; !ok {
 			t.Errorf("Expected add-on function %q", f)
@@ -445,4 +445,33 @@ func TestAlterFuncMap(t *testing.T) {
 		t.Errorf("Expected %q, got %q (%v)", expectNum, gotNum, outReq)
 	}
 
+	tplChart := &chart.Chart{
+		Metadata: &chart.Metadata{Name: "TplFunction"},
+		Templates: []*chart.Template{
+			{Name: "templates/base", Data: []byte(`Evaluate tpl {{tpl "Value: {{ .Values.value}}" .}}`)},
+		},
+		Values:       &chart.Config{Raw: ``},
+		Dependencies: []*chart.Chart{},
+	}
+
+	tplValues := chartutil.Values{
+		"Values": chartutil.Values{
+			"value": "myvalue",
+		},
+		"Chart": tplChart.Metadata,
+		"Release": chartutil.Values{
+			"Name": "TestRelease",
+		},
+	}
+
+	outTpl, err := New().Render(tplChart, tplValues)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	expectTplStr := "Evaluate tpl Value: myvalue"
+	if gotStrTpl := outTpl["TplFunction/templates/base"]; gotStrTpl != expectTplStr {
+		t.Errorf("Expected %q, got %q (%v)", expectTplStr, gotStrTpl, outTpl)
+	}
+
 }