feat: allow controllers to call __motoko_stable_var_info query endp…

…oint (#4103)

This was originally spec-ed, but there was no possibility to implement it (a canister couldn't get its own controller list).
In the meantime canisters can get their controller list (via query), but a query cannot call another query 🫤.

So we had to wait until the `ic0.is_controller` syscall became available. Now it is there and the implementation is easy.

(It was technically possible to call it before, but it invariably trapped.)

Changelog.md

@@ -1,5 +1,8 @@
 # Motoko compiler changelog
 
+  * Allow canister controllers to call the `__motoko_stable_var_info` query endpoint (#4103).
+    (Previously only self-queries were permitted.)
+
 ## 0.9.5 (2023-07-05)
 
 * motoko (`moc`)

src/ir_def/construct.ml

@@ -95,8 +95,8 @@ let primE prim es =
     | ICStableSize _ -> T.nat64
     | IdxPrim
     | DerefArrayOffset -> T.(as_immut (as_array_sub (List.hd es).note.Note.typ))
-    | NextArrayOffset _ -> T.nat
     | ValidArrayOffset -> T.bool
+    | NextArrayOffset _
     | GetPastArrayOffset _ -> T.nat
     | IcUrlOfBlob -> T.text
     | ActorOfIdBlob t -> t
@@ -111,9 +111,10 @@ let primE prim es =
     | OtherPrim "trap" -> T.Non
     | OtherPrim "call_perform_status" -> T.(Prim Nat32)
     | OtherPrim "call_perform_message" -> T.text
-    | OtherPrim "array_len" -> T.nat
-    | OtherPrim "blob_size" -> T.nat
+    | OtherPrim "array_len"
+    | OtherPrim "blob_size"
     | OtherPrim "text_len" -> T.nat
+    | OtherPrim "is_controller" -> T.bool
     | _ -> assert false (* implement more as needed *)
   in
   let effs = List.map eff es in

src/lowering/desugar.ml

@@ -438,8 +438,9 @@ and export_footprint self_id expr =
   ([ letD (var v typ) (
        funcE v (Shared Query) Promises [bind1] [] [ret_typ] (
            (asyncE T.Fut bind2
-              (blockE [expD (assertE (primE (I.RelPrim (caller, Operator.EqOp))
-                                        [primE I.ICCallerPrim []; selfRefE caller]));
+              (blockE [expD (assertE (orE (primE (I.RelPrim (caller, Operator.EqOp))
+                                             [primE I.ICCallerPrim []; selfRefE caller])
+                                        (primE (I.OtherPrim "is_controller") [primE I.ICCallerPrim []])));
                        letD size (primE (I.ICStableSize expr.note.Note.typ) [expr])
                  ]
                  (newObjE T.Object

test/run-drun/ok/query-footprint.drun-run.ok

@@ -1,7 +1,7 @@
 ingress Completed: Reply: 0x4449444c016c01b3c4b1f204680100010a00000000000000000101
 ingress Completed: Reply: 0x4449444c0000
-ingress Err: IC0503: Canister rwlgt-iiaaa-aaaaa-aaaaa-cai trapped explicitly: assertion failed at .:0.1
-Err: IC0503: Canister rwlgt-iiaaa-aaaaa-aaaaa-cai trapped explicitly: assertion failed at .:0.1
+ingress Completed: Reply: 0x4449444c016c01c1c1cee2047801005118000000000000
+Ok: Reply: 0x4449444c016c01c1c1cee2047801005118000000000000
 ingress Completed: Reply: 0x4449444c0001785118000000000000
 ingress Completed: Reply: 0x4449444c0001785118000000000000
 Ok: Reply: 0x4449444c0001712973657276696365203a207b0a202064656c65676174653a202829202d3e20286e61743634293b0a7d0a

test/run-drun/ok/query-footprint.ic-ref-run.ok

@@ -3,9 +3,9 @@
 => update install_code(record {arg = blob ""; kca_xin = blob "\00asm\01\00\00\00\0...
 <= replied: ()
 => update __motoko_stable_var_info()
-<= rejected (RC_CANISTER_ERROR): canister trapped: EvalTrapError region:0xXXX-0xXXX "canister trapped explicitly: assertion failed at .:0.1"
+<= replied: (record {size = (6225 : nat64)})
 => query __motoko_stable_var_info()
-<= rejected (RC_CANISTER_ERROR): canister trapped: EvalTrapError region:0xXXX-0xXXX "canister trapped explicitly: assertion failed at .:0.1"
+<= replied: (record {size = (6225 : nat64)})
 => update delegate()
 <= replied: ((6225 : nat64))
 => update delegate()