// getConflictFreeConfiguration loads the configuration from a JSON file.
// It compares that configuration with the one provided by the flags,
// and returns an error if there are conflicts.
func getConflictFreeConfiguration(configFile string, flags *flag.FlagSet) (*Config, error) {
b, err := ioutil.ReadFile(configFile)
if err != nil {
return nil, err
}
var config Config
var reader io.Reader
if flags != nil {
var jsonConfig map[string]interface{}
reader = bytes.NewReader(b)
if err := json.NewDecoder(reader).Decode(&jsonConfig); err != nil {
return nil, err
}
configSet := configValuesSet(jsonConfig)
if err := findConfigurationConflicts(configSet, flags); err != nil {
return nil, err
}
// Override flag values to make sure the values set in the config file with nullable values, like `false`,
// are not overriden by default truthy values from the flags that were not explicitly set.
// See https://github.com/docker/docker/issues/20289 for an example.
//
// TODO: Rewrite configuration logic to avoid same issue with other nullable values, like numbers.
namedOptions := make(map[string]interface{})
for key, value := range configSet {
f := flags.Lookup("-" + key)
if f == nil { // ignore named flags that don't match
namedOptions[key] = value
continue
}
if _, ok := f.Value.(boolValue); ok {
f.Value.Set(fmt.Sprintf("%v", value))
}
}
if len(namedOptions) > 0 {
// set also default for mergeVal flags that are boolValue at the same time.
flags.VisitAll(func(f *flag.Flag) {
if opt, named := f.Value.(opts.NamedOption); named {
v, set := namedOptions[opt.Name()]
_, boolean := f.Value.(boolValue)
if set && boolean {
f.Value.Set(fmt.Sprintf("%v", v))
}
}
})
}
config.valuesSet = configSet
}
reader = bytes.NewReader(b)
err = json.NewDecoder(reader).Decode(&config)
return &config, err
}
// findConfigurationConflicts iterates over the provided flags searching for
// duplicated configurations and unknown keys. It returns an error with all the conflicts if
// it finds any.
func findConfigurationConflicts(config map[string]interface{}, flags *flag.FlagSet) error {
// 1. Search keys from the file that we don't recognize as flags.
unknownKeys := make(map[string]interface{})
for key, value := range config {
flagName := "-" + key
if flag := flags.Lookup(flagName); flag == nil {
unknownKeys[key] = value
}
}
// 2. Discard values that implement NamedOption.
// Their configuration name differs from their flag name, like `labels` and `label`.
if len(unknownKeys) > 0 {
unknownNamedConflicts := func(f *flag.Flag) {
if namedOption, ok := f.Value.(opts.NamedOption); ok {
if _, valid := unknownKeys[namedOption.Name()]; valid {
delete(unknownKeys, namedOption.Name())
}
}
}
flags.VisitAll(unknownNamedConflicts)
}
if len(unknownKeys) > 0 {
var unknown []string
for key := range unknownKeys {
unknown = append(unknown, key)
}
return fmt.Errorf("the following directives don't match any configuration option: %s", strings.Join(unknown, ", "))
}
var conflicts []string
printConflict := func(name string, flagValue, fileValue interface{}) string {
return fmt.Sprintf("%s: (from flag: %v, from file: %v)", name, flagValue, fileValue)
}
// 3. Search keys that are present as a flag and as a file option.
duplicatedConflicts := func(f *flag.Flag) {
// search option name in the json configuration payload if the value is a named option
if namedOption, ok := f.Value.(opts.NamedOption); ok {
if optsValue, ok := config[namedOption.Name()]; ok {
conflicts = append(conflicts, printConflict(namedOption.Name(), f.Value.String(), optsValue))
}
} else {
// search flag name in the json configuration payload without trailing dashes
for _, name := range f.Names {
name = strings.TrimLeft(name, "-")
if value, ok := config[name]; ok {
conflicts = append(conflicts, printConflict(name, f.Value.String(), value))
break
}
}
}
}
flags.Visit(duplicatedConflicts)
if len(conflicts) > 0 {
return fmt.Errorf("the following directives are specified both as a flag and in the configuration file: %s", strings.Join(conflicts, ", "))
}
return nil
}