forked from drone/envsubst
/
eval.go
57 lines (51 loc) · 1.4 KB
/
eval.go
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package envsubst
import "os"
// Eval replaces ${var} in the string based on the mapping function.
func Eval(s string, mapping func(string) string) (string, error) {
t, err := Parse(s)
if err != nil {
return s, err
}
// convert mapping to match new mapper function
mapper := func(node string, key string, args []string) (string, []string, error) {
return mapping(key), args, nil
}
return t.Execute(mapper)
}
// EvalEnv replaces ${var} in the string according to the values of the
// current environment variables. References to undefined variables are
// replaced by the empty string.
func EvalEnv(s string) (string, error) {
return Eval(s, os.Getenv)
}
func EvalMap(s string, values map[string]string) (string, error) {
if values == nil {
values = make(map[string]string)
}
mapper := func(node string, key string, args []string) (string, []string, error) {
v, ok := values[key]
// return error if key not found and default not specified
if !ok && !isDefault(node) {
return "", nil, &valueNotFoundError{key}
}
// if key found, remove args for default
// so that empty value will not be replaced by default value
if ok && isDefault(node) {
return v, nil, nil
}
return v, args, nil
}
t, err := Parse(s)
if err != nil {
return s, err
}
return t.Execute(mapper)
}
func isDefault(name string) bool {
switch name {
case "=", ":=", ":-":
return true
default:
return false
}
}