Add the sprig functions in the template engine

vendor/github.com/Masterminds/sprig/defaults.go

@@ -0,0 +1,75 @@
+package sprig
+
+import (
+	"encoding/json"
+	"reflect"
+)
+
+// dfault checks whether `given` is set, and returns default if not set.
+//
+// This returns `d` if `given` appears not to be set, and `given` otherwise.
+//
+// For numeric types 0 is unset.
+// For strings, maps, arrays, and slices, len() = 0 is considered unset.
+// For bool, false is unset.
+// Structs are never considered unset.
+//
+// For everything else, including pointers, a nil value is unset.
+func dfault(d interface{}, given ...interface{}) interface{} {
+
+	if empty(given) || empty(given[0]) {
+		return d
+	}
+	return given[0]
+}
+
+// empty returns true if the given value has the zero value for its type.
+func empty(given interface{}) bool {
+	g := reflect.ValueOf(given)
+	if !g.IsValid() {
+		return true
+	}
+
+	// Basically adapted from text/template.isTrue
+	switch g.Kind() {
+	default:
+		return g.IsNil()
+	case reflect.Array, reflect.Slice, reflect.Map, reflect.String:
+		return g.Len() == 0
+	case reflect.Bool:
+		return g.Bool() == false
+	case reflect.Complex64, reflect.Complex128:
+		return g.Complex() == 0
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return g.Int() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return g.Uint() == 0
+	case reflect.Float32, reflect.Float64:
+		return g.Float() == 0
+	case reflect.Struct:
+		return false
+	}
+	return true
+}
+
+// coalesce returns the first non-empty value.
+func coalesce(v ...interface{}) interface{} {
+	for _, val := range v {
+		if !empty(val) {
+			return val
+		}
+	}
+	return nil
+}
+
+// toJson encodes an item into a JSON string
+func toJson(v interface{}) string {
+	output, _ := json.Marshal(v)
+	return string(output)
+}
+
+// toPrettyJson encodes an item into a pretty (indented) JSON string
+func toPrettyJson(v interface{}) string {
+	output, _ := json.MarshalIndent(v, "", "  ")
+	return string(output)
+}