diff options
Diffstat (limited to 'parse.go')
| -rw-r--r-- | parse.go | 76 |
1 files changed, 53 insertions, 23 deletions
@@ -1,8 +1,11 @@ package arg import ( + "errors" "fmt" + "io" "os" + "path/filepath" "reflect" "strconv" "strings" @@ -20,48 +23,74 @@ type spec struct { wasPresent bool } +// Parse returns this value to indicate that -h or --help were provided +var ErrHelp = errors.New("help requested by user") + // MustParse processes command line arguments and exits upon failure. func MustParse(dest ...interface{}) { - err := Parse(dest...) + p, err := NewParser(dest...) + if err != nil { + fmt.Println(err) + os.Exit(1) + } + err = p.Parse(os.Args[1:]) if err != nil { fmt.Println(err) + writeUsage(os.Stdout, filepath.Base(os.Args[0]), p.spec) os.Exit(1) } } -// Parse processes command line arguments and stores the result in args. +// Parse processes command line arguments and stores them in dest. func Parse(dest ...interface{}) error { - return ParseFrom(os.Args[1:], dest...) + p, err := NewParser(dest...) + if err != nil { + fmt.Println(err) + os.Exit(1) + } + return p.Parse(os.Args[1:]) } -// ParseFrom processes command line arguments and stores the result in args. -func ParseFrom(args []string, dest ...interface{}) error { - // Add the help option if one is not already defined - var internal struct { - Help bool `arg:"-h,help:print this help message"` - } +// Parser represents a set of command line options with destination values +type Parser struct { + spec []*spec +} - // Parse the spec - dest = append(dest, &internal) +// NewParser constructs a parser from a list of destination structs +func NewParser(dest ...interface{}) (*Parser, error) { spec, err := extractSpec(dest...) if err != nil { - return err + return nil, err } + return &Parser{spec: spec}, nil +} - // Process args - err = processArgs(spec, args) - if err != nil { - return err +// Parse processes the given command line option, storing the results in the field +// of the structs from which NewParser was constructed +func (p *Parser) Parse(args []string) error { + // If -h or --help were specified then print usage + for _, arg := range args { + if arg == "-h" || arg == "--help" { + return ErrHelp + } + if arg == "--" { + break + } } - // If -h or --help were specified then print help - if internal.Help { - writeUsage(os.Stdout, spec) - os.Exit(0) + // Process all command line arguments + err := process(p.spec, args) + if err != nil { + return err } // Validate - return validate(spec) + return validate(p.spec) +} + +// WriteUsage writes usage information to the given writer +func (p *Parser) WriteUsage(w io.Writer) { + writeUsage(w, filepath.Base(os.Args[0]), p.spec) } // extractSpec gets specifications for each argument from the tags in a struct @@ -143,8 +172,9 @@ func extractSpec(dests ...interface{}) ([]*spec, error) { return specs, nil } -// processArgs processes arguments using a pre-constructed spec -func processArgs(specs []*spec, args []string) error { +// process goes through arguments the arguments one-by-one, parses them, and assigns the result to +// the underlying struct field +func process(specs []*spec, args []string) error { // construct a map from --option to spec optionMap := make(map[string]*spec) for _, spec := range specs { |