Dropdown feature for Locale selection (#215)

* Add getLocales method to return locales list in PluginImpl (#211)

* Update textbox to dropdown for locale selection (#211)

* Add unit tests for PluginImpl (#211)

* Add comments to getLocales() method (#211)

* Use `f:select` and implement doFillSystemLocaleItems for better UI (#211)

* Add `Use Browser Default` Locale option (#211)

* Add `Use Browser Default` Locale option (#211)

* Fix Unit tests and bug to handle empty systemLocale (#211)

* Fix and Add Unit tests (#211)

* Fix bug in PluginImpl - MigrationTest is failing (#211)

* Add Jenkins supported Locales (#211)

* Update test for doFillSystemLocaleItems() method (#211)

* Fix the code using Spotless code style run (#211)

* Add helper text to locale limit (#211)

* Add test for systemLocale empty (#211)

* remove ionicons-api dependency (#211)

src/main/java/hudson/plugins/locale/PluginImpl.java

@@ -7,10 +7,16 @@
 import hudson.XmlFile;
 import hudson.init.InitMilestone;
 import hudson.init.Initializer;
+import hudson.util.ListBoxModel;
 import hudson.util.PluginServletFilter;
 import hudson.util.XStream2;
 import java.io.File;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
 import java.util.Locale;
+import java.util.Set;
+import java.util.stream.Collectors;
 import javax.servlet.ServletException;
 import jenkins.appearance.AppearanceCategory;
 import jenkins.model.GlobalConfiguration;
@@ -31,6 +37,14 @@ public class PluginImpl extends GlobalConfiguration {
     private String systemLocale;
     private boolean ignoreAcceptLanguage;
 
+    public static final String USE_BROWSER_LOCALE = "USE_BROWSER_LOCALE";
+
+    // Set of allowed locales
+    private static final Set<String> ALLOWED_LOCALES = new HashSet<>(Arrays.asList(
+            "bg", "ca", "cs", "da", "de", "el", "en_GB", "es", "es_AR", "et", "fi", "fr", "he", "hu", "it", "ja", "ko",
+            "lt", "lv", "nb_NO", "nl", "pl", "pt_BR", "pt_PT", "ro", "ru", "sk", "sl", "sr", "sv_SE", "tr", "uk",
+            "zh_CN", "zh_TW"));
+
     /**
      * The value of {@link Locale#getDefault()} before we replace it.
      */
@@ -74,7 +88,9 @@ public Locale get() {
     @Override
     public void load() {
         super.load();
-        setSystemLocale(systemLocale); // make the loaded value take effect
+        // make the loaded value take effect
+        if (systemLocale == null || systemLocale.isEmpty()) setSystemLocale(USE_BROWSER_LOCALE);
+        else setSystemLocale(systemLocale);
     }
 
     @Override
@@ -94,8 +110,17 @@ public String getSystemLocale() {
 
     public void setSystemLocale(String systemLocale) {
         systemLocale = Util.fixEmptyAndTrim(systemLocale);
-        Locale.setDefault(systemLocale == null ? originalLocale : parse(systemLocale));
-        this.systemLocale = systemLocale;
+        if (USE_BROWSER_LOCALE.equals(systemLocale)) {
+            Locale.setDefault(originalLocale);
+            this.systemLocale = USE_BROWSER_LOCALE;
+        } else {
+            Locale.setDefault((systemLocale == null || systemLocale.isEmpty()) ? originalLocale : parse(systemLocale));
+            this.systemLocale = systemLocale;
+        }
+    }
+
+    public String getUseBrowserLocale() {
+        return USE_BROWSER_LOCALE;
     }
 
     /**
@@ -134,6 +159,36 @@ public GlobalConfigurationCategory getCategory() {
         return GlobalConfigurationCategory.get(AppearanceCategory.class);
     }
 
+    /**
+     * Retrieves a ListBoxModel containing the available system locales.
+     * This method populates a ListBoxModel with the available system locales,
+     * sorted lexicographically by their string representations. Each locale's
+     * display name and string representation are added as options to the model.
+     *
+     * @return A ListBoxModel containing the available system locales.
+     */
+    public ListBoxModel doFillSystemLocaleItems() {
+        ListBoxModel items = new ListBoxModel();
+
+        // Use originalLocale to display the "Use Browser Locale" option
+        String originalLocaleDisplay = String.format(
+                "Use Browser Locale - %s (%s)", originalLocale.getDisplayName(), originalLocale.toString());
+        items.add(new ListBoxModel.Option(originalLocaleDisplay, USE_BROWSER_LOCALE));
+
+        Locale[] availableLocales = Locale.getAvailableLocales();
+        List<Locale> sortedLocales = Arrays.stream(availableLocales)
+                .filter(locale -> ALLOWED_LOCALES.contains(locale.toString())) // Ensure no empty or null locale strings
+                .sorted((locale1, locale2) -> locale1.getDisplayName().compareTo(locale2.getDisplayName()))
+                .collect(Collectors.toList());
+
+        for (Locale locale : sortedLocales) {
+            String displayText = String.format("%s - %s", locale.getDisplayName(), locale.toString());
+            items.add(new ListBoxModel.Option(displayText, locale.toString()));
+        }
+
+        return items;
+    }
+
     private static final XStream XSTREAM = new XStream2();
 
     static {

src/main/resources/hudson/plugins/locale/PluginImpl/config.jelly

@@ -1,8 +1,8 @@
 <?jelly escape-by-default='true'?>
 <j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form">
-    <f:section title="${%Locale}">
-        <f:entry title="${%Default Language}" field="systemLocale">
-            <f:textbox />
+    <f:section>
+        <f:entry title="${%Default Language}" help="/plugin/locale/help/help-systemLocale.html">
+            <f:select field="systemLocale"/>
         </f:entry>
         <f:entry>
             <f:checkbox field="ignoreAcceptLanguage" title="${%description}" />

src/main/webapp/help/help-systemLocale.html

@@ -0,0 +1,3 @@
+<div>
+    <p>Only a limited number of locales are available due to project scope.</p>
+</div>

src/test/java/hudson/plugins/locale/MigrationTest.java

@@ -1,6 +1,7 @@
 package hudson.plugins.locale;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 
 import jenkins.model.Jenkins;
 import org.junit.Rule;
@@ -24,4 +25,14 @@ public void dataMigration_13() {
         assertEquals("en-US", plugin.getSystemLocale());
         assertEquals(true, plugin.isIgnoreAcceptLanguage());
     }
+
+    @LocalData
+    @Test
+    public void dataMigration_UnsetLocale() {
+        PluginImpl plugin = Jenkins.get().getExtensionList(PluginImpl.class).get(0);
+
+        // Assuming the default behavior if systemLocale is unset
+        assertEquals(PluginImpl.USE_BROWSER_LOCALE, plugin.getSystemLocale());
+        assertFalse(plugin.isIgnoreAcceptLanguage());
+    }
 }

src/test/java/hudson/plugins/locale/PluginImplTest.java

@@ -0,0 +1,97 @@
+package hudson.plugins.locale;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import hudson.util.ListBoxModel;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Locale;
+import java.util.Set;
+import jenkins.model.Jenkins;
+import org.junit.Before;
+import org.junit.Rule;
+import org.junit.Test;
+import org.jvnet.hudson.test.JenkinsRule;
+
+public class PluginImplTest {
+
+    @Rule
+    public JenkinsRule j = new JenkinsRule();
+
+    private PluginImpl plugin;
+
+    @Before
+    public void setUp() {
+        plugin = Jenkins.get().getExtensionList(PluginImpl.class).get(0);
+    }
+
+    // Set of allowed locales for the test
+    private static final Set<String> ALLOWED_LOCALES = new HashSet<>(Arrays.asList(
+            "bg", "ca", "cs", "da", "de", "el", "en_GB", "es", "es_AR", "et", "fi", "fr", "he", "hu", "it", "ja", "ko",
+            "lt", "lv", "nb_NO", "nl", "pl", "pt_BR", "pt_PT", "ro", "ru", "sk", "sl", "sr", "sv_SE", "tr", "uk",
+            "zh_CN", "zh_TW"));
+
+    @Test
+    public void testDoFillSystemLocaleItems() {
+        // Invoke the method
+        ListBoxModel model = plugin.doFillSystemLocaleItems();
+
+        // Expected size of the ListBoxModel
+        int expectedSize = ALLOWED_LOCALES.size() + 1; // +1 for the "Use Browser Locale" option
+
+        // Verify the returned ListBoxModel size
+        assertEquals("The returned ListBoxModel size is not as expected", expectedSize, model.size());
+
+        // Verify that the first option is "Use Browser Locale"
+        String expectedFirstOption = String.format(
+                "Use Browser Locale - %s (%s)",
+                Locale.getDefault().getDisplayName(), Locale.getDefault().toString());
+        assertEquals("The first option should be 'Use Browser Locale'", expectedFirstOption, model.get(0).name);
+
+        // Verify that the allowed locales are correctly added to the ListBoxModel, excluding the first option
+        for (String localeStr : ALLOWED_LOCALES) {
+            Locale locale = Locale.forLanguageTag(localeStr.replace('_', '-'));
+            String expectedOption = String.format("%s - %s", locale.getDisplayName(), locale.toString());
+
+            boolean found = false;
+            for (int i = 1; i < model.size(); i++) { // Start from 1 to skip the "Use Browser Locale" option
+                if (model.get(i).name.equals(expectedOption)) {
+                    found = true;
+                    break;
+                }
+            }
+            assertEquals("The ListBoxModel does not contain the expected locale: " + locale, true, found);
+        }
+    }
+
+    @Test
+    public void testSetSystemLocale() {
+        // Test setting systemLocale
+        String systemLocale = "en_US";
+        plugin.setSystemLocale(systemLocale);
+        assertEquals(systemLocale, plugin.getSystemLocale());
+    }
+
+    @Test
+    public void testSetIgnoreAcceptLanguage() {
+        // Test setting ignoreAcceptLanguage
+        boolean ignoreAcceptLanguage = true;
+        plugin.setIgnoreAcceptLanguage(ignoreAcceptLanguage);
+        assertEquals(ignoreAcceptLanguage, plugin.isIgnoreAcceptLanguage());
+    }
+
+    @Test
+    public void testNullSystemLocale() {
+        // Test setting systemLocale to null
+        plugin.setSystemLocale(null);
+        assertNull("System locale should be null", plugin.getSystemLocale());
+    }
+
+    @Test
+    public void testEmptySystemLocale() {
+        // Test setting systemLocale to empty string
+        plugin.setSystemLocale("");
+        assertNull("System locale should be empty", plugin.getSystemLocale());
+    }
+}

src/test/resources/hudson/plugins/locale/MigrationTest.dataMigration_UnsetLocale/locale.xml

@@ -0,0 +1,4 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<locale plugin="[email protected]">
+    <ignoreAcceptLanguage>true</ignoreAcceptLanguage>
+</locale>