From 16edafb4f96ec7accf2d797d10064364b5efdd5a Mon Sep 17 00:00:00 2001
From: Grégoire Duchêne <gduchene@awhk.org>
Date: Sat, 3 Dec 2022 21:37:43 +0000
Subject: Remove ‘value’ argument from Flag{,Slice}Var
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It’s basically redundant since a pointer to the value is already
provided; callers can just set a default value there.
---
 flag.go      | 27 +++++++++++----------------
 flag_test.go |  8 ++++----
 2 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/flag.go b/flag.go
index 1931077..4506683 100644
--- a/flag.go
+++ b/flag.go
@@ -15,15 +15,14 @@ import (
 // passed ParseFunc will be used to parse raw arguments into a useful T
 // value. A valid *T is returned for use by the caller.
 func Flag[T any](fs *flag.FlagSet, name string, value T, usage string, parse ParseFunc[T]) *T {
-	p := new(T)
-	FlagVar(fs, p, name, value, usage, parse)
-	return p
+	p := value
+	FlagVar(fs, &p, name, usage, parse)
+	return &p
 }
 
 // FlagVar works like FlagT, except it is up to the caller to supply a
 // valid *T.
-func FlagVar[T any](fs *flag.FlagSet, p *T, name string, value T, usage string, parse ParseFunc[T]) {
-	*p = value
+func FlagVar[T any](fs *flag.FlagSet, p *T, name string, usage string, parse ParseFunc[T]) {
 	fs.Var(&flagValue[T]{Parse: parse, Value: p}, name, usage)
 }
 
@@ -40,18 +39,15 @@ func FlagVar[T any](fs *flag.FlagSet, p *T, name string, value T, usage string,
 // - -flag=val,val-2 -flag=val-3
 // - -flag=val,val-2,val-3
 func FlagSlice[T any](fs *flag.FlagSet, name string, values []T, usage string, parse ParseFunc[T], sep string) *[]T {
-	p := new([]T)
-	FlagSliceVar(fs, p, name, values, usage, parse, sep)
-	return p
+	p := make([]T, len(values))
+	copy(p, values)
+	FlagSliceVar(fs, &p, name, usage, parse, sep)
+	return &p
 }
 
 // FlagSliceVar works like FlagTSlice, except it is up to the caller to
 // supply a valid *[]T.
-func FlagSliceVar[T any](fs *flag.FlagSet, p *[]T, name string, values []T, usage string, parse ParseFunc[T], sep string) {
-	if values != nil {
-		*p = make([]T, len(values))
-		copy(*p, values)
-	}
+func FlagSliceVar[T any](fs *flag.FlagSet, p *[]T, name string, usage string, parse ParseFunc[T], sep string) {
 	fs.Var(&flagValueSlice[T]{Parse: parse, Separator: sep, Values: p}, name, usage)
 }
 
@@ -59,9 +55,8 @@ func FlagSliceVar[T any](fs *flag.FlagSet, p *[]T, name string, values []T, usag
 // following order: environment variables, then an arbitrary map, then
 // command line arguments.
 //
-// Note that InitFlagSet does not require the use of any of the Flag
-// functions defined in this package. Standard flags will work just as
-// well.
+// Note that InitFlagSet does not require the use of the Flag functions
+// defined in this package. Standard flags will work just as well.
 func InitFlagSet(fs *flag.FlagSet, env []string, cfg map[string]string, args []string) (err error) {
 	var environ map[string]string
 	if env != nil {
diff --git a/flag_test.go b/flag_test.go
index 1f36b63..91c6caa 100644
--- a/flag_test.go
+++ b/flag_test.go
@@ -25,8 +25,8 @@ func TestFlagVar(s *testing.T) {
 	t := core.T{T: s}
 
 	fs := flag.NewFlagSet("", flag.PanicOnError)
-	var fl int
-	core.FlagVar(fs, &fl, "test", 42, "", strconv.Atoi)
+	fl := 42
+	core.FlagVar(fs, &fl, "test", "", strconv.Atoi)
 	t.AssertEqual(42, fl)
 	t.AssertErrorIs(nil, fs.Parse([]string{"-test=84"}))
 	t.AssertEqual(84, fl)
@@ -46,8 +46,8 @@ func TestFlagSliceVar(s *testing.T) {
 	t := core.T{T: s}
 
 	fs := flag.NewFlagSet("", flag.PanicOnError)
-	var fl []int
-	core.FlagSliceVar(fs, &fl, "test", []int{42}, "", strconv.Atoi, ",")
+	fl := []int{42}
+	core.FlagSliceVar(fs, &fl, "test", "", strconv.Atoi, ",")
 	t.AssertEqual([]int{42}, fl)
 	t.AssertErrorIs(nil, fs.Parse([]string{"-test=1", "-test=2", "-test=42,84"}))
 	t.AssertEqual([]int{1, 2, 42, 84}, fl)
-- 
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