feat: Also report Motoko stable compatibility warnings (#3887)

* Report Motoko stable compatibility warnings

---------

Reviewed by: Linwei Shang <[email protected]>

Author: luc-blaeser

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 # UNRELEASED
 
+### feat: Also report Motoko stable compatibility warnings
+
+Report upgrade compatibility warnings for Motoko, such as deleted stable variables, in addition to compatibility errors.
+
 ### feat: Support for Motoko's enhanced orthogonal persistence.
 
 Support Motoko's enhanced orthogonal persistence by automatically setting the canister upgrade option `wasm_memory_persistence` based on the Wasm metadata.

e2e/assets/upgrade/v5.mo

@@ -0,0 +1,11 @@
+actor {
+  stable var newState : Int = 0;
+  public func inc() : async Int {
+    newState += 1;
+    return newState;
+  };
+  public func f() : async ?Int {
+    return ?42;
+  };
+  public query func read() : async Int { return newState; };
+}

e2e/tests-dfx/upgrade_check.bash

@@ -33,7 +33,7 @@ teardown() {
   jq '.canisters.hello_backend.main="v2_bad.mo"' dfx.json | sponge dfx.json
   echo yes | (
   assert_command dfx deploy
-  assert_match "Stable interface compatibility check failed"
+  assert_match "Stable interface compatibility check issued an ERROR"
   )
   assert_command dfx canister call hello_backend read '()'
   assert_match "(0 : nat)"
@@ -78,3 +78,17 @@ teardown() {
   assert_command dfx canister call hello_backend f '()'
   assert_match "(opt \"\")"
 }
+
+@test "warning when dropping stable variable" {
+  install_asset upgrade
+  dfx_start
+  dfx deploy
+  dfx canister call hello_backend inc '()'
+  jq '.canisters.hello_backend.main="v5.mo"' dfx.json | sponge dfx.json
+  echo yes | (
+  assert_command dfx deploy
+  assert_match "Stable interface compatibility check issued an ERROR"
+  )
+  assert_command dfx canister call hello_backend read '()'
+  assert_match "(0 : int)"
+}

src/dfx/src/lib/operations/canister/install_canister.rs

@@ -105,9 +105,13 @@ pub async fn install_canister(
         let stable_types = read_module_metadata(agent, canister_id, "motoko:stable-types").await;
         if let Some(stable_types) = &stable_types {
             match check_stable_compatibility(canister_info, env, stable_types) {
-                Ok(None) => (),
-                Ok(Some(err)) => {
-                    let msg = format!("Stable interface compatibility check failed for canister '{}'.\nUpgrade will either FAIL or LOSE some stable variable data.\n\n", canister_info.get_name()) + &err;
+                Ok(StableCompatibility::Okay) => (),
+                Ok(StableCompatibility::Warning(details)) => {
+                    let msg = format!("Stable interface compatibility check issued a WARNING for canister '{}'.\n\n", canister_info.get_name()) + &details;
+                    ask_for_consent(&msg)?;
+                }
+                Ok(StableCompatibility::Error(details)) => {
+                    let msg = format!("Stable interface compatibility check issued an ERROR for canister '{}'.\nUpgrade will either FAIL or LOSE some stable variable data.\n\n", canister_info.get_name()) + &details;
                     ask_for_consent(&msg)?;
                 }
                 Err(e) => {
@@ -375,11 +379,17 @@ async fn wait_for_module_hash(
     Ok(())
 }
 
+enum StableCompatibility {
+    Okay,
+    Warning(String),
+    Error(String),
+}
+
 fn check_stable_compatibility(
     canister_info: &CanisterInfo,
     env: &dyn Environment,
     stable_types: &str,
-) -> anyhow::Result<Option<String>> {
+) -> anyhow::Result<StableCompatibility> {
     use crate::lib::canister_info::motoko::MotokoCanisterInfo;
     let info = canister_info.as_info::<MotokoCanisterInfo>()?;
     let stable_path = info.get_output_stable_path();
@@ -399,10 +409,13 @@ fn check_stable_compatibility(
         .current_dir(canister_info.get_workspace_root())
         .output()
         .context("Failed to run 'moc'.")?;
+    let message = String::from_utf8_lossy(&output.stderr).to_string();
     Ok(if !output.status.success() {
-        Some(String::from_utf8_lossy(&output.stderr).to_string())
+        StableCompatibility::Error(message)
+    } else if !output.stderr.is_empty() {
+        StableCompatibility::Warning(message)
     } else {
-        None
+        StableCompatibility::Okay
     })
 }