fix: appId dropped when creating PropertiesCompatibleFileConfigRepository for non-default appId

DefaultConfigFactory.createPropertiesCompatibleFileConfigRepository() received an appId
parameter but called ConfigService.getConfigFile(namespace, format) — the two-arg overload
that ignores appId and resolves against the default app.id from app.properties.

Fixes the bug by:
1. Adding ConfigService.getConfigFile(appId, namespace, format) that delegates to the
   already-correct ConfigManager.getConfigFile(appId, namespace, format).
2. Updating DefaultConfigFactory to call the new three-arg overload so the caller-specified
   appId is preserved.

Adds tests:
- DefaultConfigFactoryTest.testCreatePropertiesCompatibleFileConfigRepositoryForwardsCustomAppId:
  verifies ConfigManager is invoked with the supplied appId, never the default.
- ConfigServiceTest.testGetConfigFileWithCustomAppId:
  verifies the new ConfigService.getConfigFile(appId, ns, format) overload returns a
  ConfigFile whose getAppId() equals the requested appId.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Shawyeok

apollo-client/src/main/java/com/ctrip/framework/apollo/ConfigService.java

@@ -101,6 +101,19 @@ public static ConfigFile getConfigFile(String namespace, ConfigFileFormat config
     return s_instance.getManager().getConfigFile(namespace, configFileFormat);
   }
 
+  /**
+   * Get the config file instance for the appId and namespace.
+   *
+   * @param appId            the appId of the config
+   * @param namespace        the namespace of the config, e.g. "application.yml"
+   * @param configFileFormat the config file format
+   * @return config file instance
+   */
+  public static ConfigFile getConfigFile(String appId, String namespace,
+      ConfigFileFormat configFileFormat) {
+    return s_instance.getManager().getConfigFile(appId, namespace, configFileFormat);
+  }
+
   public static ConfigMonitor getConfigMonitor(){
       return s_instance.getMonitor();
   }

apollo-client/src/main/java/com/ctrip/framework/apollo/spi/DefaultConfigFactory.java

@@ -163,7 +163,7 @@ PropertiesCompatibleFileConfigRepository createPropertiesCompatibleFileConfigRep
       String appId, String namespace, ConfigFileFormat format) {
     String actualNamespaceName = trimNamespaceFormat(namespace, format);
     PropertiesCompatibleConfigFile configFile = (PropertiesCompatibleConfigFile) ConfigService
-        .getConfigFile(actualNamespaceName, format);
+        .getConfigFile(appId, actualNamespaceName, format);
 
     return new PropertiesCompatibleFileConfigRepository(configFile);
   }

apollo-client/src/test/java/com/ctrip/framework/apollo/ConfigServiceTest.java

@@ -103,6 +103,34 @@ public void testMockConfigFactoryForConfigFile() throws Exception {
     assertEquals(someNamespaceFileName + ":" + someConfigFileFormat.getValue(), configFile.getContent());
   }
 
+  @Test
+  public void testGetConfigWithCustomAppId() throws Exception {
+    String customAppId = "customAppId";
+    String someNamespace = "mock";
+    String someKey = "someKey";
+    MockInjector.setInstance(ConfigFactory.class, someNamespace, new MockConfigFactory());
+
+    Config config = ConfigService.getConfig(customAppId, someNamespace);
+
+    assertEquals(customAppId + ConfigConsts.CLUSTER_NAMESPACE_SEPARATOR + someNamespace + ":" + someKey,
+        config.getProperty(someKey, null));
+  }
+
+  @Test
+  public void testGetConfigFileWithCustomAppId() throws Exception {
+    String customAppId = "customAppId";
+    String someNamespace = "mock";
+    ConfigFileFormat someConfigFileFormat = ConfigFileFormat.YML;
+    String someNamespaceFileName =
+        String.format("%s.%s", someNamespace, someConfigFileFormat.getValue());
+    MockInjector.setInstance(ConfigFactory.class, someNamespaceFileName, new MockConfigFactory());
+
+    ConfigFile configFile = ConfigService.getConfigFile(customAppId, someNamespace, someConfigFileFormat);
+
+    assertEquals(customAppId, configFile.getAppId());
+    assertEquals(someNamespaceFileName, configFile.getNamespace());
+  }
+
   private static class MockConfig extends AbstractConfig {
     private final String m_appId;
     private final String m_namespace;