Do not prevent ini defaults overriding builtin defaults

Issue #326.

ini.go

@@ -541,9 +541,8 @@ func (i *IniParser) parse(ini *ini) error {
 				continue
 			}
 
-			// ini value is ignored if override is set and
-			// value was previously set from non default
-			if i.ParseAsDefaults && !opt.isSetDefault {
+			// ini value is ignored if parsed as default but defaults are prevented
+			if i.ParseAsDefaults && opt.preventDefault {
 				continue
 			}
 
@@ -576,14 +575,25 @@ func (i *IniParser) parse(ini *ini) error {
 				}
 			}
 
-			if err := opt.set(pval); err != nil {
+			var err error
+
+			if i.ParseAsDefaults {
+				err = opt.setDefault(pval)
+			} else {
+				err = opt.set(pval)
+			}
+
+			if err != nil {
 				return &IniError{
 					Message:    err.Error(),
 					File:       ini.File,
 					LineNumber: inival.LineNumber,
 				}
 			}
 
+			// Defaults from ini files take precendence over defaults from parser
+			opt.preventDefault = true
+
 			// either all INI values are quoted or only values who need quoting
 			if _, ok := quotesLookup[opt]; !inival.Quoted || !ok {
 				quotesLookup[opt] = inival.Quoted

ini_test.go

@@ -903,6 +903,51 @@ func TestIniOverrides(t *testing.T) {
 	assertString(t, opts.ValueWithDefaultOverrideCli, "cli-value")
 }
 
+func TestIniOverridesFromConfigFlag(t *testing.T) {
+	file, err := ioutil.TempFile("", "")
+
+	if err != nil {
+		t.Fatalf("Cannot create temporary file: %s", err)
+	}
+
+	defer os.Remove(file.Name())
+
+	_, err = file.WriteString("value-with-default = \"ini-value\"\n")
+	_, err = file.WriteString("value-with-default-override-cli = \"ini-value\"\n")
+
+	if err != nil {
+		t.Fatalf("Cannot write to temporary file: %s", err)
+	}
+
+	file.Close()
+
+	var opts struct {
+		Config                      func(filename string) `long:"config"`
+		ValueWithDefault            string                `long:"value-with-default" default:"value"`
+		ValueWithDefaultOverrideCli string                `long:"value-with-default-override-cli" default:"value"`
+	}
+
+	p := NewParser(&opts, Default)
+
+	opt := p.FindOptionByLongName("config")
+	opt.Default = []string{file.Name()}
+
+	opts.Config = func(filename string) {
+		parser := NewIniParser(p)
+		parser.ParseAsDefaults = true
+		parser.ParseFile(filename)
+	}
+
+	_, err = p.ParseArgs([]string{"--value-with-default-override-cli", "cli-value"})
+
+	if err != nil {
+		t.Fatalf("Failed to parse arguments: %s", err)
+	}
+
+	assertString(t, opts.ValueWithDefault, "ini-value")
+	assertString(t, opts.ValueWithDefaultOverrideCli, "cli-value")
+}
+
 func TestIniRequired(t *testing.T) {
 	var opts struct {
 		Required string               `short:"r" required:"yes" description:"required"`

option.go

@@ -280,6 +280,17 @@ func (option *Option) set(value *string) error {
 	return convert("", option.value, option.tag)
 }
 
+func (option *Option) setDefault(value *string) error {
+	if err := option.set(value); err != nil {
+		return err
+	}
+
+	option.isSetDefault = true
+	option.preventDefault = false
+
+	return nil
+}
+
 func (option *Option) showInHelp() bool {
 	return !option.Hidden && (option.ShortName != 0 || len(option.LongName) != 0)
 }
@@ -309,6 +320,10 @@ func (option *Option) empty() {
 }
 
 func (option *Option) clearDefault() error {
+	if option.preventDefault {
+		return nil
+	}
+
 	usedDefault := option.Default
 
 	if envKey := option.EnvKeyWithNamespace(); envKey != "" {
@@ -327,11 +342,11 @@ func (option *Option) clearDefault() error {
 		option.empty()
 
 		for _, d := range usedDefault {
-			err := option.set(&d)
+			err := option.setDefault(&d)
+
 			if err != nil {
 				return err
 			}
-			option.isSetDefault = true
 		}
 	} else {
 		tp := option.value.Type()

parser.go

@@ -311,10 +311,6 @@ func (p *Parser) ParseArgs(args []string) ([]string, error) {
 
 	if s.err == nil {
 		p.eachOption(func(c *Command, g *Group, option *Option) {
-			if option.preventDefault {
-				return
-			}
-
 			err := option.clearDefault()
 			if err != nil {
 				if _, ok := err.(*Error); !ok {