fix: warn on effective controller removal in canister settings update

When --proxy is set, the proxy canister is the effective controller
making management calls. The self-removal warning now checks the proxy
principal instead of the caller's identity, preventing false prompts
(and "not a terminal" errors in tests) when adding controllers to
proxy-deployed canisters. Warning messages are also updated to be
accurate for each case.

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

Author: lwshang

crates/icp-cli/src/commands/canister/settings/update.rs

@@ -191,13 +191,25 @@ pub(crate) async fn exec(ctx: &Context, args: &UpdateArgs) -> Result<(), anyhow:
     if let Some(controllers_opt) = &args.controllers {
         controllers = get_controllers(controllers_opt, current_status.as_ref());
 
-        // Check if the caller is being removed from controllers
+        // Check if the effective controller is being removed from the controller list.
+        // When --proxy is set, the proxy canister is the one making management calls and
+        // is the effective controller. Without --proxy, it's the caller's identity.
+        let effective_controller = args.proxy.unwrap_or(caller_principal);
         if let Some(new_controllers) = &controllers
-            && !new_controllers.contains(&caller_principal)
+            && !new_controllers.contains(&effective_controller)
             && !args.force
         {
-            warn!("You are about to remove yourself from the controllers list.");
-            warn!("This will cause you to lose control of the canister and cannot be undone.");
+            if args.proxy.is_some() {
+                warn!(
+                    "You are about to remove the proxy canister ({effective_controller}) from the controllers list."
+                );
+                warn!(
+                    "This will prevent further management calls through this proxy and cannot be undone."
+                );
+            } else {
+                warn!("You are about to remove yourself from the controllers list.");
+                warn!("This will cause you to lose control of the canister and cannot be undone.");
+            }
 
             let confirmed = Confirm::new()
                 .with_prompt("Do you want to proceed?")

crates/icp-cli/tests/canister_settings_tests.rs

@@ -389,6 +389,8 @@ async fn canister_settings_update_through_proxy() {
             "my-canister",
             "--environment",
             "random-environment",
+            "--proxy",
+            &proxy_cid,
         ])
         .assert()
         .success()
@@ -1459,6 +1461,8 @@ async fn canister_settings_sync_through_proxy() {
             "my-canister",
             "--environment",
             "random-environment",
+            "--proxy",
+            &proxy_cid,
         ])
         .assert()
         .success()