Fix - provide default (empty) client config when default user config dir does not exist (temporalio#2828)

Author: THardy98

temporal-envconfig/src/main/java/io/temporal/envconfig/ClientConfig.java

@@ -44,13 +44,16 @@ public static ClientConfig getDefaultInstance() {
   private static String getDefaultConfigFilePath() {
     String userDir = System.getProperty("user.home");
     if (userDir == null || userDir.isEmpty()) {
-      throw new RuntimeException("failed getting user home directory");
+      return null;
     }
     return getDefaultConfigFilePath(userDir, System.getProperty("os.name"), System.getenv());
   }
 
   static String getDefaultConfigFilePath(
       String userDir, String osName, Map<String, String> environment) {
+    if (userDir == null || userDir.isEmpty()) {
+      return null;
+    }
     if (osName != null) {
       String osNameLower = osName.toLowerCase();
       if (osNameLower.contains("mac")) {
@@ -60,7 +63,7 @@ static String getDefaultConfigFilePath(
       if (osNameLower.contains("win")) {
         String appData = environment != null ? environment.get("APPDATA") : null;
         if (appData == null || appData.isEmpty()) {
-          throw new RuntimeException("%APPDATA% is not defined");
+          return null;
         }
         return Paths.get(appData, "temporalio", "temporal.toml").toString();
       }
@@ -122,6 +125,10 @@ public static ClientConfig load(LoadClientConfigOptions options) throws IOExcept
       if (file == null || file.isEmpty()) {
         file = getDefaultConfigFilePath();
       }
+      // No config dir available — return default empty config
+      if (file == null) {
+        return getDefaultInstance();
+      }
       try {
         ClientConfigToml.TomlClientConfig result = reader.readValue(new File(file));
         return new ClientConfig(ClientConfigToml.getClientProfiles(result));

temporal-envconfig/src/test/java/io/temporal/envconfig/ClientConfigProfileTest.java

@@ -325,6 +325,22 @@ public void defaultConfigFilePath() {
         ClientConfig.getDefaultConfigFilePath("/home/test", "Linux", Collections.emptyMap()));
   }
 
+  @Test
+  public void loadDefaultConfigMissingHomeDir() throws IOException {
+    String original = System.getProperty("user.home");
+    try {
+      System.setProperty("user.home", "");
+      ClientConfig config =
+          ClientConfig.load(
+              LoadClientConfigOptions.newBuilder().setEnvOverrides(Collections.emptyMap()).build());
+      Assert.assertEquals(ClientConfig.getDefaultInstance(), config);
+    } finally {
+      if (original != null) {
+        System.setProperty("user.home", original);
+      }
+    }
+  }
+
   @Test
   public void parseToml() throws IOException {
     String toml =