fix(swingset): supervisor-xs: tolerate console.log(BigInt)

We serialize console.log arguments (to send over the pipe to the kernel
process) with JSON.stringify, which doesn't tolerate BigInt. Use a simple
replacer to turn them into Numbers first; we can tolerate the loss of
fidelity for console.log.

closes #2936

packages/SwingSet/src/kernel/vatManager/supervisor-subprocess-xsnap.js

@@ -108,6 +108,13 @@ function abbreviateReplacer(_, arg) {
   return arg;
 }
 
+function bigIntReplacer(_, arg) {
+  if (typeof arg === 'bigint') {
+    return Number(arg);
+  }
+  return arg;
+}
+
 /**
  * @param { ReturnType<typeof managerPort> } port
  */
@@ -122,8 +129,10 @@ function makeWorker(port) {
    * @param { string } tag
    */
   function makeConsole(tag) {
-    const log = level => (...args) =>
-      port.send(['console', level, tag, ...args]);
+    const log = level => (...args) => {
+      const jsonSafeArgs = JSON.parse(JSON.stringify(args, bigIntReplacer));
+      port.send(['console', level, tag, ...jsonSafeArgs]);
+    };
     const cons = {
       debug: log('debug'),
       log: log('log'),

packages/SwingSet/test/workers/vat-target.js

@@ -15,6 +15,7 @@ function ignore(p) {
 
 export function buildRootObject(vatPowers, vatParameters) {
   console.log(`vat does buildRootObject`); // make sure console works
+  console.log(BigInt(0)); // make sure BigInt is tolerated: #2936
   // note: XS doesn't appear to print console.log unless an exception happens
   vatPowers.testLog('testLog works');