fix: envconfig, use OS-specific config file paths (#2762)

* use OS-specific config file paths

* address pr nits

Author: THardy98

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

@@ -5,11 +5,22 @@
 import com.fasterxml.jackson.dataformat.toml.TomlMapper;
 import io.temporal.common.Experimental;
 import java.io.*;
+import java.nio.file.Paths;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.Objects;
 
-/** ClientConfig represents a client config file. */
+/**
+ * ClientConfig represents a client config file.
+ *
+ * <p>The default config file path is OS-specific:
+ *
+ * <ul>
+ *   <li>macOS: $HOME/Library/Application Support/temporalio/temporal.toml
+ *   <li>Windows: %APPDATA%\temporalio\temporal.toml
+ *   <li>Linux/other: $HOME/.config/temporalio/temporal.toml
+ * </ul>
+ */
 @Experimental
 public class ClientConfig {
   /** Creates a new builder to build a {@link ClientConfig}. */
@@ -32,13 +43,31 @@ public static ClientConfig getDefaultInstance() {
     return new ClientConfig.Builder().build();
   }
 
-  /** Get the default config file path: $HOME/.config/temporalio/temporal.toml */
   private static String getDefaultConfigFilePath() {
     String userDir = System.getProperty("user.home");
     if (userDir == null || userDir.isEmpty()) {
       throw new RuntimeException("failed getting user home directory");
     }
-    return userDir + "/.config/temporalio/temporal.toml";
+    return getDefaultConfigFilePath(userDir, System.getProperty("os.name"), System.getenv());
+  }
+
+  static String getDefaultConfigFilePath(
+      String userDir, String osName, Map<String, String> environment) {
+    if (osName != null) {
+      String osNameLower = osName.toLowerCase();
+      if (osNameLower.contains("mac")) {
+        return Paths.get(userDir, "Library", "Application Support", "temporalio", "temporal.toml")
+            .toString();
+      }
+      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 Paths.get(appData, "temporalio", "temporal.toml").toString();
+      }
+    }
+    return Paths.get(userDir, ".config", "temporalio", "temporal.toml").toString();
   }
 
   /**

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

@@ -7,6 +7,7 @@
 import io.grpc.netty.shaded.io.netty.handler.ssl.SslContext;
 import io.temporal.serviceclient.WorkflowServiceStubsOptions;
 import java.io.*;
+import java.nio.file.Paths;
 import java.util.Collections;
 import org.junit.Assert;
 import org.junit.Test;
@@ -302,6 +303,28 @@ public void loadClientConfigProfileMissingFileReturnsDefault() throws IOExceptio
     Assert.assertNull(profile.getNamespace());
   }
 
+  @Test
+  public void defaultConfigFilePath() {
+    // macOS: ~/Library/Application Support
+    Assert.assertEquals(
+        Paths.get("/Users/test", "Library", "Application Support", "temporalio", "temporal.toml")
+            .toString(),
+        ClientConfig.getDefaultConfigFilePath("/Users/test", "Mac OS X", Collections.emptyMap()));
+
+    // Windows: %APPDATA%
+    Assert.assertEquals(
+        Paths.get("C:/Users/test/AppData/Roaming", "temporalio", "temporal.toml").toString(),
+        ClientConfig.getDefaultConfigFilePath(
+            "C:/Users/test",
+            "Windows 10",
+            Collections.singletonMap("APPDATA", "C:/Users/test/AppData/Roaming")));
+
+    // Linux: ~/.config
+    Assert.assertEquals(
+        Paths.get("/home/test", ".config", "temporalio", "temporal.toml").toString(),
+        ClientConfig.getDefaultConfigFilePath("/home/test", "Linux", Collections.emptyMap()));
+  }
+
   @Test
   public void parseToml() throws IOException {
     String toml =