fix merge issue, more tests

go-app/internal/domain/language.go

@@ -49,6 +49,15 @@ var (
 	}
 )
 
+func IsLanguageSupported(tag language.Tag) bool {
+	for _, supportedTag := range supportedLanguages {
+		if tag == supportedTag {
+			return true
+		}
+	}
+	return false
+}
+
 // GetMatcher returns the language matcher for supported languages
 func GetMatcher() language.Matcher {
 	return matcher

go-app/internal/domain/language_test.go

@@ -108,6 +108,26 @@ func TestUnsupportedSystemLanguageFallback(t *testing.T) {
 	assert.Equal(t, expectedTexts.BlankPageText, config.BlankPageText, "Blank page text should be in English")
 }
 
+func TestIsLanguageSupported(t *testing.T) {
+	tests := []struct {
+		lang language.Tag
+		want bool
+	}{
+		{language.German, true},
+		{language.English, true},
+		{language.French, true},
+		{language.Icelandic, false},
+		{language.Zulu, false},
+	}
+
+	for _, tt := range tests {
+		got := IsLanguageSupported(tt.lang)
+		if got != tt.want {
+			t.Errorf("IsLanguageSupported(%v) = %v, want %v", tt.lang, got, tt.want)
+		}
+	}
+}
+
 func TestParseLanguageCode(t *testing.T) {
 	tests := []struct {
 		name     string

go-app/internal/domain/minionTypes.go

@@ -101,8 +101,23 @@ func NewDefaultConfig(systemLanguage language.Tag) *MinionConfig {
 // MergeWith merges the current config with another config, giving precedence to the other config
 func (c *MinionConfig) MergeWith(other *MinionConfig) error {
 	if other == nil {
+		// don't change c if other is nil
 		return nil
 	}
+	// handle language separately:
+	// if other language is set, use it for all language-specific fields
+	// and set these fields to language-specific defaults.
+	if other.Language.String() != "" {
+		c.Language = other.Language
+		if IsLanguageSupported(other.Language) {
+			texts := DefaultTexts[other.Language]
+			c.ChapterPrefix = texts.ChapterPrefix
+			c.RunningHeader = texts.RunningHeader
+			c.PagePrefix = texts.PageNumber
+			c.PageCountPrefix = texts.PageCountPrefix
+			c.BlankPageText = texts.BlankPageText
+		}
+	}
 
 	// Only override non-zero values
 	if other.ConfigFileName != "" {

go-app/internal/domain/minionTypes_test.go

@@ -7,7 +7,6 @@ import (
 )
 
 func TestDefaultConfigIsEnglish(t *testing.T) {
-	// Setup a default config
 	base := NewDefaultConfig(language.English)
 
 	// the language specific values should be set to the English values
@@ -18,7 +17,6 @@ func TestDefaultConfigIsEnglish(t *testing.T) {
 }
 
 func TestDefaultConfigLanguageGerman(t *testing.T) {
-	// Setup a default config
 	base := NewDefaultConfig(language.German)
 
 	// the language specific values should be set to the German values
@@ -29,7 +27,6 @@ func TestDefaultConfigLanguageGerman(t *testing.T) {
 }
 
 func TestDefaultConfigLanguageFrench(t *testing.T) {
-	// Setup a default config
 	base := NewDefaultConfig(language.French)
 
 	assert.Equal(t, DefaultTexts[language.French].PageNumber, base.PagePrefix)
@@ -39,7 +36,7 @@ func TestDefaultConfigLanguageFrench(t *testing.T) {
 }
 
 func TestDefaultConfigLanguageUnknown(t *testing.T) {
-	// Setup a default config with an unknown language "Zulu"
+	// Set up a default config with an unknown language "Zulu"
 	base := NewDefaultConfig(language.Zulu)
 
 	// the language specific values should be set to the English values
@@ -49,11 +46,53 @@ func TestDefaultConfigLanguageUnknown(t *testing.T) {
 	assert.Equal(t, DefaultTexts[language.English].BlankPageText, base.BlankPageText)
 }
 
+// TestDefaultConfigMergeWithFlagEnglish merges an English default config with
+// --language German. The language specific values should be set to the German (default)
+func TestDefaultConfigMergeWithFlagGerman(t *testing.T) {
+	base := NewDefaultConfig(language.English)
+
+	german := &MinionConfig{
+		Language:  language.German,
+		SetFields: map[string]bool{"language": true},
+	}
+
+	// can merge without error
+	assert.NoError(t, base.MergeWith(german), "MergeWith should not return an error")
+
+	// the language specific values should be set to the German values
+	// the language specific values should be set to the German values
+	assert.Equal(t, DefaultTexts[language.German].PageNumber, base.PagePrefix)
+	assert.Equal(t, DefaultTexts[language.German].ChapterPrefix, base.ChapterPrefix)
+	assert.Equal(t, DefaultTexts[language.German].PageCountPrefix, base.PageCountPrefix)
+	assert.Equal(t, DefaultTexts[language.German].BlankPageText, base.BlankPageText)
+}
+
+// TestDefaultConfigMergeWithFlagEnglish merges an English default config with
+// --language French. The language specific values should be set to the German (default)
+func TestDefaultConfigMergeWithFlagFrench(t *testing.T) {
+	base := NewDefaultConfig(language.English)
+
+	french := &MinionConfig{
+		Language:  language.French,
+		SetFields: map[string]bool{"language": true},
+	}
+
+	// can merge without error
+	assert.NoError(t, base.MergeWith(french), "MergeWith should not return an error")
+
+	// the language specific values should be set to the German values
+	// the language specific values should be set to the German values
+	assert.Equal(t, DefaultTexts[language.French].PageNumber, base.PagePrefix)
+	assert.Equal(t, DefaultTexts[language.French].ChapterPrefix, base.ChapterPrefix)
+	assert.Equal(t, DefaultTexts[language.French].PageCountPrefix, base.PageCountPrefix)
+	assert.Equal(t, DefaultTexts[language.French].BlankPageText, base.BlankPageText)
+}
+
 func TestMinionConfig_MergeWithMinimal(t *testing.T) {
 	minimalBaseConfig := &MinionConfig{SourceDir: "/original/source"}
 	other := &MinionConfig{
 		SourceDir: "/new/source",
-		SetFields: map[string]bool{"Source": true},
+		SetFields: map[string]bool{"source": true},
 	}
 	assert.NoError(t, minimalBaseConfig.MergeWith(other), "MergeWith should not return an error")
 	assert.Equal(t, "/new/source", minimalBaseConfig.SourceDir)