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Migrating from spf13/pflag to pennant

Quick Start

Replace your import:

// Before
import "github.com/spf13/pflag"

// After
import "github.com/agentine/pennant"

Replace all pflag. references with pennant.:

// Before
pflag.StringP("name", "n", "", "your name")
pflag.Parse()

// After
pennant.StringP("name", "n", "", "your name")
pennant.Parse()

API Compatibility

pennant implements the full pflag API surface:

pflag API pennant API Notes
pflag.FlagSet pennant.FlagSet Same struct fields and methods
pflag.Value pennant.Value Same interface: String(), Set(), Type()
pflag.Flag pennant.Flag Same fields: Name, Shorthand, Usage, Value, DefValue, Changed, Hidden, Deprecated, Annotations
pflag.NewFlagSet pennant.NewFlagSet Same signature
pflag.CommandLine pennant.CommandLine Same global default
pflag.Parse() pennant.Parse() Same behavior
pflag.ContinueOnError pennant.ContinueOnError Same constants
pflag.ExitOnError pennant.ExitOnError
pflag.PanicOnError pennant.PanicOnError

Supported Types

All pflag types are supported:

  • Scalar: String, Bool, Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Float32, Float64, Duration, Count
  • Network: IP, IPNet, IPMask
  • Bytes: BytesHex, BytesBase64
  • Slice: StringSlice, StringArray, IntSlice, Float64Slice, BoolSlice, DurationSlice, IPSlice
  • Map: StringToString, StringToInt, StringToInt64

Each type has the full set of registration variants: Xxx, XxxVar, XxxP, XxxVarP, and GetXxx.

New Features

TypedFlag Generics

pennant adds type-safe flag access using Go generics:

f := pennant.NewFlagSet("app", pennant.ExitOnError)
name := pennant.TypedString(f, "name", "n", "world", "your name")
count := pennant.TypedInt(f, "count", "c", 1, "repeat count")
f.Parse(os.Args[1:])

fmt.Println(name.Get()) // string, no error or type assertion needed
fmt.Println(count.Get()) // int, no error or type assertion needed

Flag Groups

f.MarkFlagsMutuallyExclusive("json", "yaml", "table")
f.MarkFlagsRequiredTogether("username", "password")

Zero Dependencies

pennant uses only the Go standard library. No transitive dependencies.