diff options
Diffstat (limited to 'parse.go')
| -rw-r--r-- | parse.go | 134 |
1 files changed, 87 insertions, 47 deletions
@@ -43,18 +43,19 @@ func (p path) Child(f reflect.StructField) path { // spec represents a command line option type spec struct { - dest path - field reflect.StructField // the struct field from which this option was created - long string // the --long form for this option, or empty if none - short string // the -s short form for this option, or empty if none - cardinality cardinality // determines how many tokens will be present (possible values: zero, one, multiple) - required bool // if true, this option must be present on the command line - positional bool // if true, this option will be looked for in the positional flags - separate bool // if true, each slice and map entry will have its own --flag - help string // the help text for this option - env string // the name of the environment variable for this option, or empty for none - defaultVal string // default value for this option - placeholder string // name of the data in help + dest path + field reflect.StructField // the struct field from which this option was created + long string // the --long form for this option, or empty if none + short string // the -s short form for this option, or empty if none + cardinality cardinality // determines how many tokens will be present (possible values: zero, one, multiple) + required bool // if true, this option must be present on the command line + positional bool // if true, this option will be looked for in the positional flags + separate bool // if true, each slice and map entry will have its own --flag + help string // the help text for this option + env string // the name of the environment variable for this option, or empty for none + defaultValue reflect.Value // default value for this option + defaultString string // default value for this option, in string form to be displayed in help text + placeholder string // name of the data in help } // command represents a named subcommand, or the top-level command @@ -210,18 +211,31 @@ func NewParser(config Config, dests ...interface{}) (*Parser, error) { return nil, err } - // add nonzero field values as defaults + // for backwards compatibility, add nonzero field values as defaults + // this applies only to the top-level command, not to subcommands (this inconsistency + // is the reason that this method for setting default values was deprecated) for _, spec := range cmd.specs { - if v := p.val(spec.dest); v.IsValid() && !isZero(v) { - if defaultVal, ok := v.Interface().(encoding.TextMarshaler); ok { - str, err := defaultVal.MarshalText() - if err != nil { - return nil, fmt.Errorf("%v: error marshaling default value to string: %v", spec.dest, err) - } - spec.defaultVal = string(str) - } else { - spec.defaultVal = fmt.Sprintf("%v", v) + // get the value + v := p.val(spec.dest) + + // if the value is the "zero value" (e.g. nil pointer, empty struct) then ignore + if isZero(v) { + continue + } + + // store as a default + spec.defaultValue = v + + // we need a string to display in help text + // if MarshalText is implemented then use that + if m, ok := v.Interface().(encoding.TextMarshaler); ok { + s, err := m.MarshalText() + if err != nil { + return nil, fmt.Errorf("%v: error marshaling default value to string: %v", spec.dest, err) } + spec.defaultString = string(s) + } else { + spec.defaultString = fmt.Sprintf("%v", v) } } @@ -293,11 +307,6 @@ func cmdFromStruct(name string, dest path, t reflect.Type) (*command, error) { spec.help = help } - defaultVal, hasDefault := field.Tag.Lookup("default") - if hasDefault { - spec.defaultVal = defaultVal - } - // Look at the tag var isSubcommand bool // tracks whether this field is a subcommand for _, key := range strings.Split(tag, ",") { @@ -324,11 +333,6 @@ func cmdFromStruct(name string, dest path, t reflect.Type) (*command, error) { } spec.short = key[1:] case key == "required": - if hasDefault { - errs = append(errs, fmt.Sprintf("%s.%s: 'required' cannot be used when a default value is specified", - t.Name(), field.Name)) - return false - } spec.required = true case key == "positional": spec.positional = true @@ -377,27 +381,60 @@ func cmdFromStruct(name string, dest path, t reflect.Type) (*command, error) { spec.placeholder = strings.ToUpper(spec.field.Name) } - // Check whether this field is supported. It's good to do this here rather than + // if this is a subcommand then we've done everything we need to do + if isSubcommand { + return false + } + + // check whether this field is supported. It's good to do this here rather than // wait until ParseValue because it means that a program with invalid argument // fields will always fail regardless of whether the arguments it received // exercised those fields. - if !isSubcommand { - cmd.specs = append(cmd.specs, &spec) + var err error + spec.cardinality, err = cardinalityOf(field.Type) + if err != nil { + errs = append(errs, fmt.Sprintf("%s.%s: %s fields are not supported", + t.Name(), field.Name, field.Type.String())) + return false + } - var err error - spec.cardinality, err = cardinalityOf(field.Type) - if err != nil { - errs = append(errs, fmt.Sprintf("%s.%s: %s fields are not supported", - t.Name(), field.Name, field.Type.String())) + defaultString, hasDefault := field.Tag.Lookup("default") + if hasDefault { + // we do not support default values for maps and slices + if spec.cardinality == multiple { + errs = append(errs, fmt.Sprintf("%s.%s: default values are not supported for slice or map fields", + t.Name(), field.Name)) return false } - if spec.cardinality == multiple && hasDefault { - errs = append(errs, fmt.Sprintf("%s.%s: default values are not supported for slice or map fields", + + // a required field cannot also have a default value + if spec.required { + errs = append(errs, fmt.Sprintf("%s.%s: 'required' cannot be used when a default value is specified", t.Name(), field.Name)) return false } + + // parse the default value + spec.defaultString = defaultString + if field.Type.Kind() == reflect.Pointer { + // here we have a field of type *T and we create a new T, no need to dereference + // in order for the value to be settable + spec.defaultValue = reflect.New(field.Type.Elem()) + } else { + // here we have a field of type T and we create a new T and then dereference it + // so that the resulting value is settable + spec.defaultValue = reflect.New(field.Type).Elem() + } + err := scalar.ParseValue(spec.defaultValue, defaultString) + if err != nil { + errs = append(errs, fmt.Sprintf("%s.%s: error processing default value: %v", t.Name(), field.Name, err)) + return false + } } + // add the spec to the list of specs + cmd.specs = append(cmd.specs, &spec) + // if this was an embedded field then we already returned true up above return false }) @@ -680,11 +717,14 @@ func (p *Parser) process(args []string) error { } return errors.New(msg) } - if !p.config.IgnoreDefault && spec.defaultVal != "" { - err := scalar.ParseValue(p.val(spec.dest), spec.defaultVal) - if err != nil { - return fmt.Errorf("error processing default value for %s: %v", name, err) - } + + if spec.defaultValue.IsValid() && !p.config.IgnoreDefault { + // One issue here is that if the user now modifies the value then + // the default value stored in the spec will be corrupted. There + // is no general way to "deep-copy" values in Go, and we still + // support the old-style method for specifying defaults as + // Go values assigned directly to the struct field, so we are stuck. + p.val(spec.dest).Set(spec.defaultValue) } } |