inspector: rewrite inspector test helper

Helper was rewritten to rely on promises instead of manually written
queue and callbacks. This simplifies the code and makes it easier to
maintain and extend.

PR-URL: nodejs#14460
Reviewed-By: James M Snell <jasnell@gmail.com>

test/common/README.md

@@ -99,6 +99,15 @@ Tests whether `name` and `expected` are part of a raised warning.
 
 Checks if `pathname` exists
 
+### fires(promise, [error], [timeoutMs])
+* promise [<Promise]
+* error [<String] default = 'timeout'
+* timeoutMs [<Number] default = 100
+
+Returns a new promise that will propagate `promise` resolution or rejection if
+that happens within the `timeoutMs` timespan, or rejects with `error` as
+a reason otherwise.
+
 ### fixturesDir
 * return [<String>]
 

test/common/index.js

@@ -814,6 +814,32 @@ function restoreWritable(name) {
   delete process[name].writeTimes;
 }
 
+function onResolvedOrRejected(promise, callback) {
+  return promise.then((result) => {
+    callback();
+    return result;
+  }, (error) => {
+    callback();
+    throw error;
+  });
+}
+
+function timeoutPromise(error, timeoutMs) {
+  let clearCallback = null;
+  let done = false;
+  const promise = onResolvedOrRejected(new Promise((resolve, reject) => {
+    const timeout = setTimeout(() => reject(error), timeoutMs);
+    clearCallback = () => {
+      if (done)
+        return;
+      clearTimeout(timeout);
+      resolve();
+    };
+  }), () => done = true);
+  promise.clear = clearCallback;
+  return promise;
+}
+
 exports.hijackStdout = hijackStdWritable.bind(null, 'stdout');
 exports.hijackStderr = hijackStdWritable.bind(null, 'stderr');
 exports.restoreStdout = restoreWritable.bind(null, 'stdout');
@@ -827,3 +853,19 @@ exports.firstInvalidFD = function firstInvalidFD() {
   } catch (e) {}
   return fd;
 };
+
+exports.fires = function fires(promise, error, timeoutMs) {
+  if (!timeoutMs && util.isNumber(error)) {
+    timeoutMs = error;
+    error = null;
+  }
+  if (!error)
+    error = 'timeout';
+  if (!timeoutMs)
+    timeoutMs = 100;
+  const timeout = timeoutPromise(error, timeoutMs);
+  return Promise.race([
+    onResolvedOrRejected(promise, () => timeout.clear()),
+    timeout
+  ]);
+};