diff options
| -rw-r--r-- | flag.go | 13 | ||||
| -rw-r--r-- | flag_test.go | 9 |
2 files changed, 22 insertions, 0 deletions
@@ -82,6 +82,12 @@ func InitFlagSet(fs *flag.FlagSet, env []string, cfg map[string]string, args []s return } + if f.DefValue != f.Value.String() { + if _, ok := f.Value.(MutableFlagValue); !ok { + return + } + } + var next string if val, found := environ[strings.ToUpper(strings.ReplaceAll(f.Name, "-", "_"))]; found { next = val @@ -102,6 +108,13 @@ func InitFlagSet(fs *flag.FlagSet, env []string, cfg map[string]string, args []s return err } +// MutableFlagValue is used to signal whether it is safe to set a flag +// to another value if it has already been set before, i.e. if its +// current value (as a string) is the same as its default value. +type MutableFlagValue interface { + MutableFlagValue() +} + // ParseString returns the string passed with no error set. func ParseString(s string) (string, error) { return s, nil diff --git a/flag_test.go b/flag_test.go index 26568d6..1f36b63 100644 --- a/flag_test.go +++ b/flag_test.go @@ -110,4 +110,13 @@ func TestInitFlagSet(s *testing.T) { t.AssertEqual(tc.expStr, *fm) }) } + + t.Run("NoMutableFlagValue", func(t *core.T) { + fs := flag.NewFlagSet("", flag.PanicOnError) + fi := fs.Int("int", 0, "") + t.AssertErrorIs(nil, core.InitFlagSet(fs, nil, nil, []string{"-int=42"})) + t.AssertEqual(42, *fi) + t.AssertErrorIs(nil, core.InitFlagSet(fs, nil, nil, []string{"-int=21"})) + t.AssertEqual(42, *fi) + }) } |