fix: fix error on decoding service type (#731)

* fix error on decoding service type

* changelog

* fix

* fix

* fix

* fix

* fix

* add back test

docs/generated/changelog.html

@@ -20,6 +20,9 @@ <h2>Version x.x.x</h2>
         <li>
           fix: typo in JsonnableWebAuthnIdentitiy, breaking change that requires users to update their imports to JsonnableWebAuthnIdentity when this type is used
         </li>
+        <li>
+          fix: fix a bug in decoding service types, when function types come after the service type in the type table
+        </li>
       </ul>
       <h2>Version 0.15.7</h2>
       <ul>

packages/candid/src/idl.test.ts

@@ -180,7 +180,9 @@ test('IDL encoding (arraybuffer)', () => {
   IDL.encode([IDL.Vec(IDL.Nat8)], [new Uint8Array()]);
   IDL.encode([IDL.Vec(IDL.Nat8)], [new Uint8Array(100).fill(42)]);
   IDL.encode([IDL.Vec(IDL.Nat16)], [new Uint16Array(200).fill(42)]);
-  expect(() => IDL.encode([IDL.Vec(IDL.Int8)], [new Uint16Array(10).fill(420)])).toThrow(/Invalid vec int8 argument/);
+  expect(() => IDL.encode([IDL.Vec(IDL.Int8)], [new Uint16Array(10).fill(420)])).toThrow(
+    /Invalid vec int8 argument/,
+  );
 });
 
 test('IDL encoding (array)', () => {
@@ -349,6 +351,12 @@ test('IDL encoding (service)', () => {
     '4449444c026a0171017d00690103666f6f0001010103caffee',
     'service',
   );
+  testDecode(
+    IDL.Service({ foo: IDL.Func([IDL.Text], [IDL.Nat], []) }),
+    Principal.fromText('w7x7r-cok77-xa'),
+    '4449444c02690103666f6f016a0171017d0001010103caffee',
+    'service',
+  );
   test_(
     IDL.Service({ foo: IDL.Func([IDL.Text], [IDL.Nat], ['query']) }),
     Principal.fromText('w7x7r-cok77-xa'),

packages/candid/src/idl.ts

@@ -1796,8 +1796,17 @@ export function decode(retTypes: Type[], bytes: ArrayBuffer): JsonValue[] {
   }
 
   rawTable.forEach((entry, i) => {
-    const t = buildType(entry);
-    table[i].fill(t);
+    // Process function type first, so that we can construct the correct service type
+    if (entry[0] === IDLTypeIds.Func) {
+      const t = buildType(entry);
+      table[i].fill(t);
+    }
+  });
+  rawTable.forEach((entry, i) => {
+    if (entry[0] !== IDLTypeIds.Func) {
+      const t = buildType(entry);
+      table[i].fill(t);
+    }
   });
 
   const types = rawTypes.map(t => getType(t));